A Field Kit for Critical Thinking

This post is the final lesson to students in my Spring 2020 anatomy courses, which were disrupted mid-semester by the COVID-19 pandemic. In our live sessions, it was fun to help them sort through the rampant misinformation and promising leads on COVID-19 treatment, and they asked if we could keep meeting throughout the summer. Maybe we will, but in any case, I hope that this guide gives them a few last pointers on how to survive in this bizarre new era.

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We live in the Misinformation Age.

Open your news feed, Facebook, or your inbox full of emails from That One Uncle we all have, and you’re going to be tangled in wild and contradictory claims about science. Left, Right, and Center… if humans are involved, then people are going to be spinning B.S. It’s enough to drive many to despair - nothing is real, everything is dumb - but hear me out, there’s hope!

A side perk of taking a science course is that it should give you a few new tools out of the Field Kit for Critical Thinking. As you stride forward into the strange days ahead, I hope you’ll wield these to cut through this dense forest of B.S. and keep you and yours out of trouble. These tools work together, but in rough order of use:

TOOL 1: Check your dang sources! What is the claim, is it accurately reported, and what evidence supports it?
On the face of it, this is the easiest to do and doesn’t have to be particularly time-consuming. Unless you’re a practicing scientist in a narrow field, very few of us sit down with a cup of coffee and a scientific journal to read hardcore primary research. Everything else is filtered through a different outlet: a University press release, a newspaper, a dedicated science aggregator (like sciencenews.org), or entertainment media. The further you get from the original science, the more likely you are to encounter outright errors or severe distortion of the research findings. So, what do we do?

First, demand a source if one isn’t provided. Lots of claims can be immediately exposed as, er, “creative narrative” with no basis in reality. To be charitable, there are some fanciful imaginations out there! Everyone is entitled to their own opinion, but not their own facts. Despite many recent arguments to the contrary, facts are still a thing (convenient or otherwise) and we can objectively learn about the universe using reason and evidence. Willfully ignoring facts because you don’t like them is magical thinking, is prevalent throughout the political spectrum, and is extremely dangerous.

Next, quickly check out the source. Is it from a remotely credible outlet [more on this in Tools 2 + 3]? If not, can you cross-check it with other, more trustworthy sources? For something sufficiently important, or if you’re embroiled in an argument with someone, there’s no substitute for going to the original research… except that much of the time, this is behind a paywall or completely opaque to non-experts. Are there discrepancies in how different sources are reporting the claim, such as numbers not matching up, how the conclusions are being spun, and so on?

If you take one thing away from this, it’s this key from the legendary Carl Sagan: Extraordinary claims require extraordinary evidence. Despite what typical, formulaic science reporting would have you believe, scientists aren’t constantly “baffled” and don't have to “have to rewrite the textbooks” three times a week. Science very seldom moves forward in huge leaps! Mature fields have a good idea of what’s going on in their little corner of science, and new evidence mostly refines that understanding or fills in gaps. Completely overturning a robust explanation of something requires pretty darn strong evidence to justify it. For example, we have a deep understanding of how viruses in general work and respond to treatment, so it would take an awful lot of careful studies with strong conclusions to substantially change that model. Similarly, our understanding of new fields (like the biology and treatment of COVID-19, a novel virus) can be modified quickly based on decent evidence. If we don’t yet firmly grasp what’s going on, lots of little nudges in the same direction can bring about large changes in our understanding.

Most people live their daily lives this way: if you have a very good reason to believe something, it takes a lot to convince you otherwise; but if you aren’t sure, it’s easier. Science is fundamentally different from matters of faith because if the evidence is strong enough, good scientists are obligated to change their minds. In short, “keep an open mind, but not so open that your brain falls out.”

TOOL 2: Evaluate expertise! Is this person really qualified to make that claim?
Now we’re getting into the tougher stuff. Who is making the claim in your (hopefully) credible source? In descending order, here’s who you should trust to accurately report a claim:
1) The scientists who did the original research (the claim will be undistorted, but seek corroboration of its significance [see Tool 3 below]);
2) Other scientists in that same narrow field;
3) Non-partisan governmental organizations responsible for overseeing research and making recommendations, like the CDC;
4) Relatively unbiased and accurate media outlets reporting news, NOT Opinion articles that are easily confused with news, even in otherwise legitimate outlets. Here is a link to a widely used media bias chart that can help you assess sources.
5) Everyone else.

Number 5 is where the real danger comes in. To see why, let’s pause to talk about expertise.

Expertise means having true mastery of a skill or knowledge. This isn’t something you get in a day, a week, or a year; expertise is earned over many dedicated years of study and practice. Consider a master electrician, a physician, or someone who has run a restaurant for 30 years. Expertise is real, powerful, and very narrow in scope. Just as you don’t want a dentist installing new gas lines in your home, or a skilled carpenter taking out your gall bladder, those with expertise need to stay in their lane. Unfortunately, there’s a trap here. It’s all too easy for those with expertise in one specific field to incorrectly assume that they are also experts in other fields that may or may not be closely related to their area of mastery! “I am the world’s expert in how viruses replicate their genomes, and therefore I can confidently talk about how viruses spread in a population.” Uh, no. You really can’t. These “appeals to authority” are a very common informal logical fallacy, and unfortunately, lots of otherwise brilliant people get themselves into trouble this way. It’s particularly visible among older Nobel laureates, who sometimes start spouting nonsense using the exposure won through their past successes.

Here’s the best way I’ve found to help people avoid falling into this trap, particularly if they’re older, confident adults with expertise of their own (for example, relatives at Thanksgiving…). Say your uncle spent his career designing jet engines. Ask him how much he thinks the general public understands about designing jet engines, versus his personal expertise. He’ll laugh and say, “not a darn thing!” Then gently point out that this is how the experts in any field feel about EVERYONE ELSE outside of that field. Experts in vaccine development recognize that you know “not a darn thing!” about vaccine safety, just as they know nothing of designing jet engines. Intellectually honest people should really stop and reflect on that for a while.

Those who don’t absorb this lesson exemplify what’s called the Dunning-Kruger effect (and look this up, it’s wild). In short, people with the least knowledge about a subject most strongly overestimate their knowledge of it! It’s easy to understand why: they don’t know enough to know what they don’t know. Yeah, read that again. If you’ve ever walked into a test feeling like a rockstar, but then completely bombed it because you didn’t realize that you were unprepared… that’s Dunning-Kruger. We’ve all been there.

Clearly, no one can be an expert on everything. Your professors are typically world experts in one very specific topic, and they can (with varying degrees of success) extend that expertise to teach you about the broader field. Hopefully they are honest about that and will tell you, when they start to get outside of their lane, “That’s a great question! I don’t know, but I’ll find out!” On many occasions in my courses, particularly when we covered something so truly bizarre/horrifying that it stretched belief, I would always make a point of encouraging you to fact-check me. Some of you would do that, and return with haunted eyes. That’s implied in every lesson for every class you will ever take: trust, but verify.

Why am I belaboring this explanation of expertise? I warned you that there’s a danger here, and it’s in confusing experts in a field who can credibly comment on a claim (#2 above) with experts in different fields who aren’t staying in their lanes but are seen as authorities because of their unrelated expertise and credentials (#5). For examples, let’s talk about two prominent media personalities who have been back in the news lately: Dr. Oz and Dr. Phil.

Dr. Mehmet Oz is an accomplished cardiac surgeon on the faculty at Columbia University. He also hosts a television program in which he makes dubious medical claims about supplements and other interventions. Independent evaluators have demonstrated that at least half of these are either inaccurate or totally baseless. In fact, he was summoned to testify before Congress, and an attempt was made at formal censure by the American Medical Association. Why would he do this? We’ll think about that below in Tool 3. Recently, although he has zero expertise in epidemiology or virology, he has regularly appeared on TV programs making claims about COVID-19 that are again contradicted by best evidence.

For more on the highly questionable practices of Dr. Oz, check out this article in the American Medical Association’s Journal of Ethics.

Dr. Phil McGraw, another television personality raised to prominence by Oprah Winfrey, is a clinical psychologist… not even a physician and not licensed to practice (check out his Wikipedia biography for some sordid details). Like Dr. Oz, he has also been back on the media circuit making claims about COVID-19, and his celebrity has granted him a platform to talk about something that is very far indeed from his area of expertise. So, uh. Why do people do this?

TOOL 3: Evaluate motivations! What are they trying to sell you… and what are you trying to sell to yourself?
When someone makes a claim, always ask yourself: what are they trying to sell me? Everyone is trying to sell you something… otherwise, they wouldn’t be engaging with you in the first place. Much of the time, this will be some kind of political/policy stance, meant to influence you to their side (and reinforce their own opinions too). They may be trying to sell you a physical product, with convenient links on their website. They may even just be sowing chaos for “fun,” like typical online trolls. Some do all of these at once! Alex Jones, the prominent host of InfoWars, has built an empire selling bogus conspiracy theories and physical products. The cornerstone of his legal defense during a custody trial for his children (which he lost) was that he is a “performance artist” and his InfoWars personality is a dramatized character not meant to be taken seriously. This is important context for his legions of dedicated fans, particularly as he continues to insert himself into national politics… as a self-proclaimed cartoon character.

Fear is an incredibly powerful motivator, driving people to want clear-cut and simple solutions (or denials) of their problems. Bad actors thrive in this environment, making it more important than ever to tread lightly and use your tools. If everyone is trying to sell you something, find the “products” that are most legitimately fact-based, helpful, and transparent. If you’re looking at an accurately reported claim [Tool 1], made by a governmental body like the CDC that is typically apolitical and charged with tracking the progress of a pandemic and the nation’s response [Tool 2], then they are most likely trying to “sell” you a fact-based set of recommendations on how to keep yourself safe and improve national outcomes. If you’re looking at a medical claim without cited supporting evidence [Tool 1], by a TV personality with a very poor track record of providing accurate advice [Tool 2], and they receive promotional consideration ($) for touting that product while maintaining their national brand [Tool 3], it’s probably B.S. In his response to a formal complaint by other physicians, Dr. Oz said he presents his claims “without conflict of interest.” Well sure, if you totally ignore the money and airtime; the estimated net worth of Dr. Oz is disputed, but in the tens of millions of dollars at the low end of the range. The most famous huckster in history, P.T. Barnum, recognized that when people are given a choice between attractive “humbug” and cold, hard reality… reality doesn’t stand a chance.

That is a deeply important lesson, and one that brings us to our last point. What are you trying to sell to yourself?

Everyone suffers from cognitive biases… it’s just how humans work. We want certain things to be true because they reinforce our values, our self-image, or are otherwise attractive or reassuring. In many cases, bright people with expertise can become even more susceptible to B.S. because they are skilled at motivated reasoning, coming up with justifications for false beliefs that sound plausible but don’t stand up to scrutiny. If you really want something to be true, take a step back and carefully reassess why you want it to be true and the extent to which that influences your view of the claim. Oh man, does this take practice. Motivated reasoning has never been more of an attractive nuisance than it is today in the Misinformation Era of narrowcast media. It is easier than ever to get trapped in an echo chamber of identical, self-reinforcing viewpoints that may or may not correlate with reality. Navigating this strange world, just like success in science, requires an awful lot of humility. Recognize that your expertise is limited, that you are probably wrong about many things in ways both large and small, and that the search for Truth is going to require you to cut through that forest of B.S. seeded daily by swindlers, politicians, and otherwise well-meaning but confused people. Hidden in this shady grove are still some good folks trying to help.

It’s wild out there. Good luck - I believe in you.

-NA

And another one

So Iowa has embraced a horrific Race To The Bottom, considering and too often adopting wildly regressive policies statewide. One of the latest is House File 7, introduced by a particularly benighted member of the State House, which would effectively extend vaccination exemptions to anyone who just doesn't really feel like participating.

I took exception to this and, as is my custom, made my opinion known.

The QC Times published my letter today; please check it out. Text below, for archival purposes.

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This letter is in regard to House File 7, the bill that would broaden vaccination exemptions in Iowa.

This is not a personal freedom issue, this is a public health crisis. Just as we no longer allow our streets to serve as open sewers, nor our ER waiting rooms to be cigar lounges, we should not open the door to vaccination exemptions that will only lead to the resurgence of easily preventable diseases. A population of vaccinated, healthy adults provides “community immunity,” keeping the most vulnerable members of our society - infants, cancer patients, transplant recipients - from catching potentially fatal infections.

In attempting to advance the noble cause of personal freedom, this bill’s authors seem to have missed the point that that your personal freedom stops at my, or my child’s, body.

It is ironic that the only reason that this bill is even under consideration is that vaccines have been tremendously effective at pushing the horrific epidemics of the past into fading memory. Listen to the pediatricians. Vaccination is both the moral and the rational choice.

Neil Aschliman, Ph.D.
Davenport

Letter to the editor

I've gotten old.

Once upon a time, I relished a good fight. It helped that I was a student of evolutionary biology at a university of around forty thousand who were decidedly neither Down With It nor afraid to show it. I'll never know who produced them, but maroon "Darwin Lied - Genesis 1:1" shirts were as commonplace as "Truth" fish, devouring Darwin sigils, on vehicles. I wanted a piece. Nineteen-year old business majors at the coffee shop, professing a profound mastery of biochemistry and physics that "disproved evolution"? Baited hooks. Mostly harmless crackpot Tom Short spouting nonsense on a sunny day in the quad, rocking Hawaiian shirts and six-day creationism? Blood in the water.

I was the kid who was first up on the mike in the Q&A sessions following engineers/executives/whatever who were brought in to attempt to discredit science. I could never understand why most of my professors, and in particular a short, irascible Yankee, would never get involved. Save one bizarre and ill-advised [more on this in a moment] debate between our department chair and Mike Behe, poster boy of Intelligent Design (think Creationism with a spoiler) and some weird beers out afterward, most of the silverbacks would just shake their heads and listen to me vent.

I loved the fight. Upon meeting Genie Scott, former director of the National Center for Science Education, while I was in grad school, I probably would have quit on the spot to accept a job offer.

I've gotten old.

...but I haven't given up the fight. It took me a long time to realize that my advisors weren't choosing to abstain, to abdicate some responsibility to the maintenance of sanity and reason in society. They were just doing it smarter, and they didn't have the teenage Gibraltar-on-one's-shoulder that I bore. They knew that Some Men You Just Can't Reach. Indeed, that's why I would go spar with Tom Short; not to win anyone over, but to correct any gross falsehoods (and boy, were there some howlers!) that he or his scions would sling to see what stuck.

These guys just coolly breathed science and reason into everything they did in class. Arguably the best positioned to do so was not the Evo prof, but rather the mild-mannered and brilliant guy teaching Embryology. There is perhaps no better class for demonstrating key principles of both evolution and development, and without the Day One stigma to the recalcitrant of a class called "Evolution."

This is the best that we can do through science. Demonstrate how evolution is the only remotely viable lens through which to view the objective reality of life on Earth; in other words, Daniel Dennett's "universal acid." This has so far been my joy of the semester - teaching a small but bright group of students how "Life found a way" across the scope of biodiversity.

So what do we do for everyone else? Not for the pre-physical therapist or budding researcher, but for the lawyers and librarians and contractors of the world, who are every bit as bright but are neither a captive nor particularly interested audience (on average)?

The one thing we should not do is consent to the entirely sisyphean, futile prospect of public debate. I've seen it in our Chair vs. Behe, in Bill Nye vs. Ken Ham. Civil debates work, and only work, if the participants present data that are generally recognized to be credible and can bolster one perspective or position or the other. That is most definitely not how "debates" over evolution vs. creationism work. Please indulge a dramatic reenactment:

Participant A: "Here is something that is the case."
Participant B: "That is false."
Audience: "Well, crap. I guess we have to go look everything up when we go home."

And, without fail, people will cleave to their narrowcast sources of choice and will reinforce their previous opinions irrespective of anything that actually transpired on stage. It certainly doesn't help that much of the subject matter is esoteric as all get-out; see coverage of the Dover v. Kitzmiller trial if you want to visualize a judge's eyes rolling back in his head from days of testimony over the majestic bacterial flagellum.

I have been invited to participate in such a debate, and I will no more fall into this snare than engineers on the Apollo project will debate moon landing hoaxers. The optimal outcome is that I would do a passable job of defending the notion that we can use our minds to learn more about objective reality, with the inevitable side effect of lending credence to mysticism by elevating it to a position of false equivalency and providing the opposition with exposure and a fund-raising opportunity.

It worked out pretty well for Ken Ham, and we was trashed by The Science Guy.

So. Uh. Why are we here today? Because this letter to the editor was published in our local paper last week, and I saw in it an opportunity to respond from a less conventional perspective.

Probably the thing I love most about my school, which is a church-affiliated institution, is the opportunity it's given me to befriend and collaborate with bright, thoughtful theologians. Last spring, I gave a joint lecture with my buddy on the Biology and Theology of Monsters ("T-Rex vs. Leviathan" - more on this in upcoming posts), and our friendship has broadened my perspectives on the historical interplay between religion and science / natural philosophy.

The truth is that young-earth creationism is a bankrupt philosophy that in its current, fundamentalist form is surprisingly young and born of a rejection of societal change. Think of it as a weed. Refuting (again, ultimately up to the audience to fact-check claims with reputable sources, a grueling exercise) scientific claims one-by-one is like snipping the terminal leaves of the weed. It won't kill or keep it in check.

You have to go for its deep roots, exposing them as deeply and philosophically rotten: science is not inherently evil nor anti-religious, and indeed science and religion have been and continue to be two complementary Tools of Knowing for most of humanity.

When I chose to respond to the creation "science" letter, I knew it was fruitless to lance sciencebolts from on high. I took the other path. Here is the link to the QC Times letter, which is edited and for which I am trying hard not to read the comments, although I was pleasantly surprised by the retorts to the creationists' post. Below, I reprint the original, uncut letter.

I hope my nineteen-year old self would approve. My biologist and theologian friends have.

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To address Mr Brouard’s comments in his recent letter:

The claim that science must “hide behind judges” is one of the most astonishing bits of misdirection I have seen outside of the caucuses. It is in fact creationists who have fled to litigation as well as legislation after being soundly defeated in court. From 2004 to 2011, over forty “academic freedom” bills promoting creationism in public school science classes were filed in 13 states. Science and rational thought are on defense for once.

Mr Brouard lists several prominent scientists who believed in a Creator. This is irrelevant. All of these men were also white males. Are only theistic, white males capable of good science? The tremendous technological achievements of recent decades suggest otherwise.

The statement about “falsehoods” is a mishmash of, ironically, abject falsehoods and straw men. Trotting out old Haeckel’s drawings to undermine modern biology is akin to denying modern astronomy because early sketches of Mars were inaccurate. Just as we now have rovers and orbiters exploring the red planet, biology has advanced to a degree that Mr Brouard would likely find incredible.

Finally, the idea that science leads inevitably to atheism belies a poor understanding of both theology and history. This is known as the “wedge strategy” of those who recognize that they can’t win with science. Historically, scientists used natural philosophy as a way to interpret creation and God’s design. Metaphors in the Bible were understood to be just that: symbols. Biblical literalism is a surprisingly recent contrivance of Western society.

Creationism is head-in-the-sand denialism that is neither science nor sound philosophy. It obscures two of the most beautiful truths of all: the objective history of life on Earth, and our place in God’s creation. Science and religion can be in harmony if we use evidence and our gift of reason to shine light on the How of creation, and our hearts to understand the Why.

Neil C. Aschliman, Ph.D.

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After publication, I received a voicemail invitation to debate, as well as a letter from the NCSE that mentioned cribbing my "head-in-the-sand denialists" line and made me geek out pretty hard.

It was a good day.

The Devil Ray's in the Details

So mantas aren't a thing anymore... - paraphrase, David Shiffman's liveblog of my talk at the recent meeting of the American Elasmobranch Society.

Wow, is that going to require some explanation! Did I steal these guys away under cover of night? Did they pull a "so long, and thanks for all the fish" on us? No, this is a story about the power of naming, and one that may have serious implications for the conservation of these amazing animals and their close relatives.

Human beings love to name things. We do it vigorously and redundantly: a single fish species may be christened with a dozen or more common names by people in different geographic areas, times, or even marketing departments! It helps to have an international-standard system of naming animals to give this enterprise some consistency. It doesn't matter if you know it as Chilean Sea Bass or the Patagonian Toothfish, people worldwide will be happy to confirm for you that Dissostichus eleginoides is indeed one ugly customer.

This system of precise identification in which scientists apply a formal code to name organisms is called binominal nomenclature ("two-part name"). This is often incorrectly called "binomial" nomenclature ("two number," a mathematical expression), even by professionals! The first part of the name is the genus, which can apply to between one and many species that are closely related and resemble each other. The second part of the name is the specific epithet, which applies to one and only one species. These names are usually derived from Greek and Latin. For example, Batrachognathus volans translates as "flying frog-jawed" one, an apt appellation for an odd pterosaur from the Late Jurassic.

A genus (plural genera) should describe some small set of similar organisms. This group should be defined by a common ancestor, all of its descendants, and nothing else (Figure 1A). We call these natural groups, or clades.

This is the ideal case. What happens if you end up with something like Figure 1B? Here, you can see that one genus is "nested" inside the other one: Mobula is not a natural group because it inappropriately excludes Manta. It's easy to analogize this to how, in some cultures, family names are passed down the paternal line. If you, your father, his father, and all male relatives in between are named "Lannister" but one of your brothers is named "Baratheon," something's gone wrong in the process of naming!

Under the current classification scheme, there are two genera of "devil rays": two species in the genus Manta and nine species in the genus Mobula. Besides some slight differences in body proportions, there are a few characteristics that distinguish Manta from Mobula. Most notably, Manta lack teeth on the upper jaw and have a mouth at the end of the head, while the mouth of Mobula is underslung as in most sharks. In recent years it has usually been held that the classification of devil rays is a valid arrangement, following Figure 1A.

However...

Evidence from both DNA sequences and comparative anatomy suggests that current devil ray classification actually fits Figure 1B, making it invalid.

DNA sequence analyses from my doctoral dissertation work ^[1], followed by a large-scale study performed by my graduate advisor and colleagues ^[2], suggested that Manta is nested within Mobula. While not all species were sequenced, Manta birostris was indicated to be more closely related to Mobula japanica than it is to other sequenced Mobula. This is based mostly on evidence from one or two genes, with a couple of others rather uninformative. It was compelling enough to get me to delve back through the scientific literature on the anatomy of the group, and what I found was surprising.

It turns out that biologists who have taken a close look at devil ray anatomy have been quietly suggesting for nearly 15 years that Mobula is not a natural group! ^[3,4] For example:

 • Most devil rays have comb-like teeth, while Manta, Mobula japanica, and Mobula mobular have distinctive peg-like teeth. ^[3,4]

 • Mobula japanica (>3m wide) and Mobula mobular (>5m?) are among the largest devil rays, comparable in size to the recently described Manta alfredi. ^[5,6]

 • Among devil rays, only Manta, Mobula japanica, and Mobula mobular have caudal spines (the "sting" in "stingrays"). ^[5,6]

So is this enough to overturn the current system of classification for devil rays? Not yet. If any changes are to be proposed, someone first needs to perform a formal "taxonomic revision" of both Manta and Mobula. This means that they need to present a sound, peer-reviewed case for the reclassification of these species, which will require physically re-examining them and ideally presenting corroborating DNA evidence. This must include the "type species" for each genus: Manta birostris and Mobula mobular. A type species is the one to which the name of the genus is permanently attached; in this case, it defines "what a Mobula should be." There are to date no available DNA sequence data for Mobula mobular, although we can predict that they will group most closely with Manta and Mobula japanica.

Assuming the evidence continues to build that Manta is nested within Mobula, what happens next? The most likely case is that the genus Manta will cease to be valid, subsumed under Mobula as a "junior synonym." Mobula has precedence under the rules since it was described in 1810, versus 1829 for Manta. There are mechanisms by which a name can be suppressed: the proposed renaming of the fruit fly species that's the cornerstone of much of modern biology would be a nightmare beyond measure (see here), but Manta is unlikely to qualify. Their common names will remain "Manta Rays" and the world will go on turning. Given the scarcity of materials from some species and their often colossal size, I don't envy the gal/guy to undertake the formal review of the devil rays... but it needs to be done. Five bucks says that Manta is going away in the next ten years.*

So why does this matter? Legal issues and conservation.

Savvy folks sitting in the conference room or reading David's liveblog quickly seized upon this question. With Manta recently receiving protection under the Convention on International Trade in Endangered Species (CITES), would lumping these guys in with Mobula expose them (1) under a legal technicality and/or (2) as less unique and worthy of conservation than when they had their own genus? Fortunately, shark conservation experts including Sonja Fordham (President at Shark Advocates International / Deputy Chair at IUCN Shark Specialist Group / conservation rockstar) were on hand to address these concerns.

Fears of CITES loopholes appear to be unfounded. Current protection schemes are thought to be engineered to continue to protect the two named (plus a third suspected but undescribed) species of Manta. Prying at loopholes is sadly unnecessary: countries that would otherwise seek to do so can apparently just opt out of CITES protections (I am aiming an unimpressed glare squarely at you, Canada and Guyana).

In short, this is less a threat to mantas than it may be an opportunity to extend protections to the other devil rays. Most of these species are heavily affected by both targeted fisheries and as bycatch, but they exhibit human-like life histories that make them extremely vulnerable to such pressure. Despite this shared and imminent danger, only Manta - with its tremendous charisma - seems to have found many champions in conservation, evidenced by the fact that only Manta species were proposed for CITES listing. Changing its name won't make these folks give up the cause, but folding all of the devil rays into a single genus can underscore the similarities in vulnerability across species in this group, strengthening the case for offering them equal safeguards in the future.

"Mantas aren't a thing anymore"? Sounds good to me.

*Offer valid for first claimant as of ten years from the date of this article's publication. If I win, I'll pick one of you at random and demand my fiver.

References
¹ Aschliman NC (2011) The batoid tree of life: recovering the patterns and timing of the evolution of skates, rays and allies (Chondrichthyes: Batoidea). Dissertation, Florida State University
² Naylor GJP, Caira JN, Jensen K, Rosana KAM, Straube N, Lakner C (2012) Elasmobranch phylogeny: a mitochondrial estimate based on 595 species. In: Carrier JC, Musick JA, Heithaus MR (eds) Biology of sharks and their relatives, 2nd edn. CRC Press, Boca Raton, Florida, pp 31-56
³ Herman J, Hovestadt-Euler M, Hovestadt DC, Stehmann M (2000) Contributions to the study of the comparative morphology of teeth and other relevant ichthyodorulites in living supra-specific taxa of Chondrichthyan fishes. Part B: Batomorphii 4c: Order: Rajiformes - Suborder Myliobatoidei - Superfamily Dasyatoidea - Family Dasyatidae - Subfamily Dasyatinae - Genus: Urobatis, Subfamily Potamotrygoninae - Genus: Potamotrygon, Superfamily Plesiobatoidea - Family Plesiobatidae - Genus: Plesiobatis, Superfamily Myliobatoidea - Family Myliobatidae - Subfamily Myliobatinae - Genera: Aetobatus, Aetomylaeus, Myliobatis and Pteromylaeus, Subfamily Rhinopterinae - Genus: Rhinoptera and Subfamily Mobulinae - Genera: Manta and Mobula. Addendum 1 to 4a: erratum to Genus Pteroplatytrygon. Bull Inst R Sci Nat Belg Biol 70:5-67
⁴ Adnet S, Cappetta H, Guinot G, Notarbartolo di Sciara G (2012) Evolutionary history of the devilrays (Chondrichthyes: Myliobatiformes) from fossil and morphological inference. Zool J Linn Soc 166:132-159
⁵ Notarbartolo di Sciara G (1987) A revisionary study of the genus Mobula Rafinesque, 1810 (Chondrichthyes: Mobulidae), with the description of a new species. Zool J Linn Soc 91:1-91
⁶ Marshall AD, Compagno LJV, Bennett MB (2009) Redescription of the genus Manta with resurrection of Manta alfredi (Krefft, 1868) (Chondrichthyes; Myliobatoidei; Mobulidae). Zootaxa 2301:1-28

Photos from Wikimedia Commons
Manta: LINK
Mobula: LINK

Shattering the Vegetarian Myth: Meat Consumption Was Intrinsic to Human Evolution

Apologies for the absence. It takes time to finish one life and start another.

At least this dragged me back into the scene: Kathy Freston's "Shattering the Meat Myth: Humans Are Natural Vegetarians." The piece is, and I hesitate to write this in an age where one's Google News feed bears a striking resemblance to The Onion, a breathtakingly poor scrap of doggerel. Even for ill-researched propaganda, this beast is remarkable in its reckless and wanton distortion of not only science, but of history as well.

This rebuttal in no way touches upon the relative morality or nutrition of diets that include or exclude animal products. In fact, the article came to my attention via Facebook by a respected friend and colleague who takes a valid moral stance against meat consumption. However, with 20,000 other Facebook Likes at the moment, I cannot let the grotesque inaccuracy of the arguments from biology stand. To crib from Samuel L. Jackson's character in Pulp Fiction, "Well, allow me to retort!"

Freston argues as follows (and by all means, read the original to evaluate my summary).
1. The inclusion of meat in the human diet is a product of agricultural civilization (circa 10,000 years ago) and is incompatible with a plant-based biochemistry that dates back "at least tens of millions of years." Prior to the rise of herding, "we may have needed a bit of meat… in times of scarcity."
2. "Humans are herbivores" because we lack physical adaptations that make it easy to tear flesh and hide, such as overdeveloped canine teeth and claws. We resemble the other great apes in that we process food with our hands and must have similarly had "a largely plant-based diet."
3. Humans have "never adapted" to a meat-inclusive diet because meat-eaters have a higher incidence of heart disease, cancer, and diabetes.

Freston's deeply flawed arguments can be attacked from historical, evolutionary, and logical angles. Let's get the observed history out of the way so we can get on to the evo.

A History of Meat Consumption
Let us assume, for the purposes of clarity (since Freston surely provided little), that the "natural" state of humanity refers to traits expressed prior to civilization and its concomitant horrors. Freston has asserted that, before the advent of agriculture-dependent herding 10,000 years ago, humans consumed only small quantities of meat in times of hardship.

Um. But.

This ignores the physical record of at least 70,000 years of hunting. Hunting big things. From some of the earliest human art on cave walls depicting the hunt, to no shortage of archaeological sites riddled with thousands of mammoth bones (one example), remains of other large and small mammals, deep middens of fish bones and mollusk shells, and so on. By about 10,000 years ago, we were in part responsible for the disappearance of nearly every large mammal in the Western Hemisphere by eating them toward extinction.

South African cave art. Photo Credit San Felszeichnung, from Wikimedia Commons.

Of course, then civilization struck and, well… a grand total of zero of the remotely successful cultures on the planet, now or in recorded history, have categorically excluded meat from their diet. Jared Diamond has a little more to say on the subject.

But let's throw Freston a bone (hah) and examine her argument in the time frame of millions of years. What does biology have to say?

Pretty Much The Same Thing
Freston views humanity through the lens of our closest living relatives, the other great apes, so let's follow. Our sister group, the two chimpanzee species, eat lots of lovely fruits and vegetable bits. Er, and also insects, birds, and mammals including other primates and small relatives of cows and pigs(!). Meat only comprises about 5% of their caloric intake, but for a species relying on its hands, primitive tools and wits, it's seriously impressive that they can muster as much.

Is Freston correct that the human gut tract is like the intestines "of other herbivores" in being very long? No, we're rather intermediate on the spectrum between hypercarnivores and herbivores. Incidentally, carnivore gut tracts are not particularly short "so they can quickly get rid of all that rotting flesh they eat" - another of the bountiful instances in which Freston's sensationalism throws science on the fire. Carnivores have a short and efficient intestinal tract in that they don't need to process large quantities of generally indigestible plant fibers. Our barrel-shaped rib cages, rather than the conical arrangement exhibited by primates that consume more plant matter, in part reflects this reduction in gut length.

Freston laments the absence of wicked claws and fangs (actually, in primates the size of the canine teeth is strongly correlated with social structure rather than with diet) and such. If only humans had a way of compensating for that!

Oh. Right. The whole running and tools thing.

A proper treatment is well beyond the scope of this post, but the evolution of the human body plan from that of a four-footed ancestor appears to have been driven in large part by selective pressure on the ability to run long distances efficiently - and later, while holding tools. Our legs and feet are superbly adapted to long distance running. The NYT has a decent, if brief summary of a few of these characters, and there's a skeletal outline of the endurance running hypothesis over at Wiki. This ability may be nearly 2 million years old, dating back to Homo erectus.

There are a couple reasons for us to run long distances: to poach kills (in fact, that's how we got tapeworms from large cats and hyenas), and to run prey into the ground. Turns out we're pretty good at that (awesome Attenborough video!). We run, we track, and unlike many of our large prey, we can sweat to cool off in the chase. Persistence pays off.

Might meat consumption have put evolutionary pressure on not only our body plans, but on our developmental timing as well? Humans wean their offspring at a very early age relative to other great apes (2 years and change in humans / 5 in chimps / 7 in orangutans, which consume very little animal protein). This is a pattern common to carnivorous mammals (PLoS ONE original). Carnivores wean their offspring faster than do herbivores due to improved milk quality and/or the ability of the offspring to eat high-energy meat. After weaning, females again become receptive to mates; the upshot is that a shorter weaning period increases reproductive capacity.

The preponderance of evidence suggests that Freston's thesis could not be more wrong. The increased means to acquire and utilize meat was likely one of the major driving forces behind the evolution of our bipedal body plan optimized for endurance running, our ability to make and manipulate tools, and our developmental timing. There are other human relatives that were more clearly geared toward eating tough plant matter. They didn't make it.

But It'll Still Kill You
Meat is an extremely efficient source of nutrients, including proteins, fats, vitamins, and minerals. When combined with leafy greens and other nutritious foods and an active life style, it helps build healthy bodies. In the short term. In the long term, the consumption of, in particular, red and processed meats is linked to increased risk of cardiovascular disease, certain cancers, and diabetes.

Apparently needing a screamingly ludicrous sound bite from an otherwise distinguished individual, Freston concludes her sad crusade with this gem from Dr. William Roberts, editor of the American Journal of Cardiology. In its entirety: "Although we think we are, and we act as if we are, human beings are not natural carnivores. When we kill animals to eat them, they end up killing us, because their flesh, which contains cholesterol and saturated fat, was never intended for human beings, who are natural herbivores." Coupled with another MD suggesting that "our bodies have never adapted to [eating meat]," it begs the obvious question: why did our ancestors eat meat - and as we have seen above, they certainly did - if it predisposed them to disease? The answer, again, rests in timing.

Except in cases of gross excess and sedentary life styles, these pathologies tend to strike late in life. Specifically, they largely affect post-reproductive (or nearly so) individuals. If you die at 55 from a heart attack but raise ten vigorous, meat-fed offspring, you still have dramatically higher fitness than a vegetarian who lives to 90 but raised five offspring before menopause. Additionally, during the course of human history, "post-reproductive" is a luxury that an incredibly small portion of the population would ever live to see; those disorders would be invisible to natural selection. The MDs' argument is completely vacuous. While they may mean well, I won't stand by to see them misinform the public in order to do so.

It's good to be back.

[Note: Desmond Morris tackled the evolution of humans as a balancing act between carni- and herbivory in his classic The Naked Ape.]

A Day Late and a Dollar Short

Please forgive the absence. June was spent running analyses and putting together my talk for the Joint Meeting of Ichthyologists and Herpetologists (nerds working on fishes and reptiles/amphibians, respectively) in Providence. Two glad tidings: I have returned to wax scientific on subjects, and I was honored to receive the ASIH Stoye award in General Ichthyology at the conference. Before the year is out, I will write an article here on the same: what the interrelationships of batoid fishes, my study group (skates, rays and allies), can tell us about widespread convergent evolution and the effects of the end-Cretaceous extinction event on their current patterns of diversification.

Speaking of mass extinction...

This one has been a while coming. Toward the end of last year, several science news outlets picked up a striking article in the journal Biological Conservation. In short, it suggested that current guidelines for setting minimum population sizes for protected species, like the black rhinoceros, are at least an order of magnitude (10x) too low to adequately protect them from extinction in this century. The current guidelines adhere to a "50/500" rule, in which a minimum of 50 adults are required to avoid the negative effects of inbreeding, and a minimum of 500 to be able to adapt to long-term environmental changes or rebound from a catastrophic event.

Ten times too low. Put a big, flashing exclamation point at the end of that one. Horrifying corollaries are immediately evident: many species are already too far gone to be preserved in the long term even if we dropped everything to triage them now, and species we think we've done a bang-up job of protecting to date may just need one calamity to drop them below that point of no return. In light of the political difficulties - an understatement by any measure - of maintaining even today's meager/modest conservation measures, a tenfold increase will never happen. These species, humble to majestic, mountain gorilla (~400) to desert pupfish (42!), are going away sooner than we'd like.

It is not an encouraging picture.


Black rhinoceros. Photo credit John and Karen Hollingsworth, USFWS, from Wikimedia Commons.

This is not a political blog, so we'll leave the issue behind and look at what these numbers mean. Why do we need X number of animals to avoid catastrophe? The first barrier, inbreeding, is intuitively obvious: offspring are produced by close genetic relatives. Put another way, the two copies that an individual carries of each her genes have a high probability of being identical by descent, or having come from the same ancestor (grandma) independently through each parent. Gross, yeah. But why is this necessarily a bad thing? Every human has two identical copies - alleles - of at least some genes, and we're not all running around with horrible genetic abnormalities. Things go south (no pun intended; I am from Texas after all) when you deal with genes that have a healthy version and a defective one.

At many gene locations in your DNA, you have one healthy allele and one defective one. In most cases, the normal copy steps up and does a stalwart job compensating for the freeloader. You'll never notice that one copy is bad, and so we call that copy a recessive, or hidden allele. That's the good news. The bad news is that they're ticking time bombs on a generational timescale. When you reproduce, one of those alleles is "drawn" at random to end up in your sperm or eggs. If you pass on the healthy version, great, your child will be A-OK for that gene. If not, you'd better hope that your mate contributes a healthy copy to pull the weight for your freeloader. If two recessive alleles end up in the offspring, she won't be able to make that gene's normal protein product. The effects may be mild, and even desirable to some: blond hair or blue eyes. Or instead, they may cause a serious genetic malady like cystic fibrosis or sickle cell anemia. If you have one healthy and one hidden, defective allele for a disease-associated gene, you are a carrier. Everyone on the planet is a carrier for an unknown, but probably not inconsiderable, number of genetic disorders. This is the basis behind genetic testing, which is becoming cheaper and more widely available every year.

The rest is easy to follow. If you're a cheetah and there are only a handful of your species left (the cheetah-reality is not that dire), the odds that you are closely related to any other cheetah you see are much higher than they are for a species with larger population sizes, like industrialized humans. If you mate with that cheetah, your odds of having the same set of alleles from a common ancestor are high, and an increasing proportion of offspring will either have two healthy or two defective copies of a gene - allele fixation. You can see how the situation degrades quickly once disease traits become universal in a population. Lost genetic diversity takes a long, long time to be recovered.

The second, higher requirement for a minimum viable population size (the 500 of the 50/500 rule) is trickier to understand. It builds on the concept of inbreeding, but the higher number of organisms keeps a larger gene pool - the total genetic variation in a population - available into the future. High genetic variation gives a population options, so to speak, in the face of environmental change. There may be warmer-adapted cheetah alleles that would do better under increased temperatures, or slightly faster cheetahs that can better keep up with Thomson's gazelles, which are under similar pressures. Perhaps most importantly, it provides options for [pathogenic] disease resistance.

Viruses, bacteria, and other parasites are engaged in a constant arms race with their hosts at a molecular level. Genetic variability goes a long way to ensure that at least some cheetahs will survive a potent disease, while if they are genetically homogeneous, a single bacterial strain that has "figured them out" can wipe out the whole population in one fell swoop. As a great recent example, humans of European descent have a much higher incidence of a genetic mutation called CCR5-delta32 that provides resistance to HIV. This mutation also appears to confer resistance to the great historical European plagues. That is, some Europeans had this mutant allele and became resistant to plague, while other didn't and were selected against. If Europe's population had been much smaller, this mutation may have never arisen and the entire continent could have been taken out in one of those dread epidemics.

A grim picture, to be sure. The next steps are political, but having been introduced to the science, hopefully you are in a better position to weigh the costs and benefits of conservation measures for yourself.

Here's to an educated democracy.

This reView of Life(?): Viruses, Part 2

The first decade of this brave new century was characterized by dramatic upheavals, often violent, in politics, business... and film. Perhaps through widespread disillusionment in the wake of crises in security and finance, perhaps merely the pendulum swinging back from the fantastic (read: "divorced from reality") flavors of storytelling in the 1980s - early 90s, the public has rushed to embrace the gritty and believable. Joel Schumacher's candy-colored Batman films were usurped by Christopher Nolan's dark masterpieces, achieving almost ridiculous commercial success. Peter Jackson breathed life into a vision of The Lord of the Rings that eschewed most of the magic and occasional levity of the book, and also featured a rather mundane, if attractive, aesthetic. Additional existing franchises and concepts from other media leapt to the big screen or were rebooted, and surprisingly often attempt to feature some "scientific" hook to enhance the believability of the tale. One of the rising stars of this movement is our enigmatic acquaintance, the virus.

Viruses are now almost universally implicated as the nefarious causal agent in modern zombie tales or close cousins, such as the animalistic, deranged "infected" in 28 Days Later. Alas, the point of this article is not to tackle the questionable physiology of a zombie (actually, that sounds like a good one for another day), but rather to touch on Hollywood's mixed success in portraying the pathology of viruses.


The virus in 28 Days Later is particularly terrifying in that, 30 seconds after exposure, a victim is reduced to a hemorrhaging, raging volcano of virus-laden fluids. One infected person in a crowd can effect some sick parody of The End Times in mere minutes. Viruses in many other films spread with similar urgency, in some cases reanimating a corpse within two minutes of exposure (Dawn of the Dead reboot). What does the real world have to say about this?
©2002, 20th Century Fox.

Viruses are constrained by the same physical laws that the rest of us are, regardless of your definition of "life." A generic viral life cycle, and there are all sorts of bizarre variants, goes something like this:
 1) find a host cell;
 2) enter the host cell, or inject genetic material;
 3) use own or hijacked machinery to replicate genes and coat proteins;
 4) stay forever, or have all your copies erupt out of the host cell;
 5) repeat.

Each of these steps requires time, particularly step (3). This is even more of a problem for related scifi concepts involving rapid gains of animal/plant/fungal tissue, or what I call "The Werewolf Problem." I'll leave that for another day.

The window of time between initial exposure and the point at which symptoms first emerge is called the incubation period. During incubation, viruses are reproducing and spreading through host cells but are at insufficient numbers to make much of an impact. Yet. So how long is this timetable? Clearly 30 seconds for complete system takeover is unrealistic.

The fastest acting human virus, as far as I have been able to discover, is the stringy little fiend below, ebola. The incubation period of ebola is 2 - 21 days, but usually 5 - 18 [source: Emerging infectious diseases 9(11):1430-7; via Wikipedia]. The fastest.


Ebola virus. Photo Credit Centers for Disease Control, from Wikimedia Commons.

A common pattern of viral strategies is a correlation between their agressiveness and their ability to be transmitted. Ebola and similar viruses have evolved a strategy that is very much living (yes, I said it) on the edge. They emerge, spread and kill so quickly that they run the risk of not being able to find a new host and suffering local extinction. Compare this to the less common strain of the virus that causes AIDS, HIV-2. HIV-2 often degrades the immune system more slowly than does HIV-1, leading to higher long-term survival rates. It also is less successful at being transmitted between people. For an analogy in honor of the ongoing NBA finals, it may only shoot 60% from the field compared to HIV-1's 80%, but gets an extra five minutes of playing time. The natural world is full of these trade-offs, in which organisms fine-tune their life strategies over time.

The ones that fail? Well. We don't see those guys anymore.

On that note, next time I will likely bring up some recent, distressing speculations about the fates of endangered species.

This reView of Life(?): Viruses, Part 1

There are no absolutes in science. The closest you'll get is in physics, but most of the so-called Laws remain either fundamentally unexplained and/or not quite what we thought they were. If asked to name one "obvious truth" about the natural world, I suspect most folks would immediately come up with something about gravity. "If I let go of this cute kitten, it will fall." But would you believe that we have almost no idea why this is so? We have nothing but competing theoretical frameworks for why things fall, and to get more technical, why gravity should exactly equal an object's inertia. No [prevailing] idea whatsoever. To make matters worse, gravity appears to "misbehave" at astronomical distances. The concepts of dark matter and dark energy are stabs at explaining why our observations of big objects' movement through the universe do not at all conform to expectations under gravitational theory, and our most distant manmade satellites are typically not where we expected them to be. The explanations could be mundane... or not.

Biology is far messier, if much better understood. In fact, as a biologist it is difficult to even define our field! Think on this for a moment: how would you define life? Which set of characteristics makes something living, from people to peas to protists? Let us consider two different candidates.

The first is from NASA, whose stalwart crew of scientists are engaged in the very business of finding weird, unexpected kinds of life out there in the big empty.

"Life is a self-sustained chemical system capable of undergoing Darwinian evolution."


For a different perspective, let's go to the textbook I'm using to teach non-majors intro bio this summer, Essential Biology by eds. Campbell, Reece & Simon.
"The set of common characteristics that distinguish living organisms, including such properties and processes as order, regulation, growth and development, metabolism, response to the environment, reproduction, and the capacity to evolve over time."

Clearly there's something going on behind the scenes to have two such dramatically different definitions. NASA's definition is more inclusive, which is to be expected when anticipating exotic forms of "life," but what exactly are the textbook makers ruling out?

Why, it is your friend and mine, the pesky little bugger that's had me coughing and cursing for the last week: the virus.

Viruses and bacteria are together responsible for most human infectious diseases, but are fundamentally very different things. A bacterium is an organism by any definition, composed of a single discrete unit called a cell. Its arrangement into wholly or semi-autonomous cells puts it in the same league as all other life (by the textbook definition) on Earth: it grows, it divides, it responds to stimuli, and as an imperfect reproducer its populations are capable of change over time.

The virus is not a cell. Writers for pop media often get this dead wrong. For example, consider an episode of the current Fox television series Fringe. The show features both surprisingly excellent characters and some of the mostly howlingly terrible "science" I've ever seen. A sluglike parasite used in assassinations was revealed to be a genetically engineered supersized cold virus "cell." Sigh.

Viruses are actually a diverse grab-bag of maybe-organisms consisting, at a minimum, of genetic information and a protective coat. The info can be stored either as DNA, as in all cellular life on Earth, or as its chemical cousin RNA. The coat is made of protein and sometimes fats. A virus is basically the nasty hacker of the biosphere: it comes into contact with some cellular organism, injects its genetic material, and hijacks that cell's machinery to make more copies of the virus. In some cases, the cell basically explodes in order to release a swarm of new viruses. Other, more sinister viruses actually incorporate themselves into the host's DNA and "hitch a ride." Potentially forever. A good deal of the so-called "junk DNA" in your genome is actually viral information: some dormant, some not so much!

How do you fight something like that? We have antibiotics against cellular organisms, like bacteria: chemical compounds that selectively interfere with the pest's way of life. Not so with viruses. Antibiotics have zero effect on them, and are actually counterproductive in that they give rise to resistant strains of bacteria that can then feel free to rise up and take on humanity. Vaccination is currently the best defense against viruses, since the limited supply of drugs that can actually hamper the viral life(?) cycle often do a good deal of damage to the patient's cells too.

So. What do viruses lack that makes some consider them non-living? Do they possess order/structure? Of course; take a look at this micrograph of swine flu. So does ice, great. Reproduction? Check, but so does fire. Evolution? Yes oh yes. Metabolism? That one's a maybe, since it hijacks a host cell's metabolic machinery. The "problem" lies in virus' inability to directly grow (although they self-assemble) and, more importantly, maintain an internal environment different from what's outside their coat.
Swine flu (H1N1). Photo Credit C. S. Goldsmith and A. Balish, CDC, from Wikimedia Commons.

Okay, I could buy that, except some bacteria run into the same problem when they face certain stresses. In these circumstances they form spores, which are dormant, hardcore, last-chance structures used to ride out what would otherwise be certain death. Some important causes of human disease form spores, like the agents behind anthrax and botulism. Spores do not have metabolism, do not reproduce, do not grow, do not maintain that internal environment... they are basically virus-like, waiting for favorable circumstances before developing back into bacteria. While a bacterium may form a spore while it waits for nutrients to come along, viruses wait for new host cells.

Personally, I side with NASA and find it hard to call spores and viruses nonliving. There is a tremendous gulf between viruses and uncontroversially nonliving particles, far greater than that between viruses and some bacterial stages. At worst, viruses are renegade bits of life. Hypotheses of the origins of viruses, events which have probably occurred innumerable times through the history of life on Earth, usually stipulate these bits of genetic information "going rogue" and escaping the cell with the bare minimum of machinery for propagating themselves. Once they're out in the biosphere, evolution takes over and all hell breaks loose.

And that's what life is all about.

Next time: touching again on the misrepresentation of viruses in pop culture, particularly movies.

Brief Hiatus for A Related Project

Sorry for the extended absence. I'm currently writing my unit of this summer's Intro Bio for Non-Majors, which poses many interesting problems. Moreso given that I drew the "Cell and Genetics" unit, which is the driest by far of the lot. My task is thus: condense and sugar-coat a colossal and diverse set of fields into eight lectures for people who really, really don't want to be there.

So far, my syllabus includes includes beer, Ridley Scott's Alien, Maury, Jurassic Park, and mass extinction among others. I think I'm going to focus on three things: the molecular nature of life (and the nebulous definition of the latter), diseases/disorders, and how to recognize bad biology in movies, tv and other pop culture.

I suspect that I may adapt one or two of those topics for this blog.

Back soon.
-NA

Sharks, Stasis and Fake ID

You've heard it before: "Sharks are among Earth’s oldest life-forms," [Discovery Channel] having patrolled the seas, "essentially unchanged, for 400 million years" [National Geographic]. Among the most prevalent of sharky soundbites, gems like these are sensationalistic, misleading, and born of a strange sort of biased observation. Let's see if we can't challenge their grim persistence.

What of the first claim, that sharks are Very, Very Old? This one is repeated so often as to be clichéd and conceals an interesting and quite different reality. All living sharks (and rays, to which we'll return in a moment) are descended from a common ancestor dating to the Triassic Period, probably somewhere between 240 - 220 million years ago. This makes the set of all living sharks and rays about the same age as dinosaurs and, surprisingly, just a hair older than mammals! So how do they get away with the perception that they're almost twice as old as that: the paleontological equivalent of an eleven-year old bellying up to the bar and scoring a beer?

It turns out that living sharks and rays are the only survivors of a much older and previously much larger set of fishes. Collectively known as chondrichthyans, or fishes-with-cartilage-skeletons, this crew is at least 400 million years old and was both amazingly diverse and often bizarre in appearance. Calling a more recently derived subset (living sharks and rays) of this ancient group 400 million years old is like calling me 200 years old because that's how far back I can trace my lineage. It doesn't work.


Cladoselache, an early chondrichthyan. From Wikimedia Commons.

So when people speak of sharks as being twice as old as dinosaurs, they're hopefully not referring to the age of the living group (although I fear this is often the case), but rather to the broader idea of "the shark." This is a different concept, that of the body plan or general architecture of the beast. Torpedo-shaped, toothy, with the typically sharky complement of fins slicing through the water. In doing so, they are placing "the shark" in the same bin as "the shrimp": an artificial group of organisms that pretty much look the same. Critically, this ignores 400 million years of weird experiments in the shark body plan. Just a few examples of extinct chondrichthyans include forms that resemble lumpy rocks, or eels with a long spine behind their head, or strange little undersea birds, or one with a spiral of teeth that no one quite knows where to place on the fish. For some beautiful reconstructions of these oddities, check out this article in Dive Magazine.

And let's not forget about those living exceptions that happen to comprise the group I study: the rays. Rays, skates and their relatives (collectively called batoids) are the majority of living shark and ray species, and precious few of them look anything like sharks. One colleague has gone so far as to call her skates "charismatic slimy pancakes of wonder." The group also includes what is considered to be the most derived, non-sharklike chondrichthyan of all, the manta ray.


Manta ray. Photo credit Richard Harvey, from Wikimedia Commons.

With this background, we can finally address the second claim. Has the shark body plan remained "essentially unchanged" over deep time? [Some creationist websites claim zero change, which is ludicrious to anyone with eyes and Google - try it yourself.] The answer to this question is more complex than that of the first.

At first blush, it seems simple. Having defined "the shark" as a body plan rather than as a natural set of organisms, the comparison between ancient and modern sharks is revealed to be circular. We've designated starting and ending points based on their similarity and then raise our eyebrows when they turn out to be similar. Wow. Consider an analogy from finance. If a trader tracks a thousand stocks over the course of a year, most will finish either up or down from their starting price. A few will finish at, or close enough to, their initial value. Is it then meaningful for the trader to ignore all but those few static stocks, and in his bias marvel at how little they've changed over time?

But fortunately the natural world isn't the DJIA, and perhaps there is some kernel of wisdom that we can salvage from this debacle. Just how similar are the body plans of shark-like chondrichthyans today and those of 400 million years ago? There have been important modifications to jaw suspension, the internal girdles supporting the paired fins, and so on, but much beyond that we're going out of bounds of our artificial body plan playing field. Sharks' hydrodynamic, torpedo-shaped architecture is what some biologists cheekily call A Good Trick: a trait that a group retains or multiple groups independently stumble upon because it's highly adaptive for their environment and way of life.

In one last attempt to address the question, let's turn for perspective to sharks' sister group, the osteichthyans or fishes-with-bony-skeletons. There are two subsets of these: the ray-finned fishes, which are nearly all "typical" fishes (see last week's post); and the lobe-finned fishes, which include coelacanths, lungfishes, and limbed vertebrates like... you! Both ray- and lobe-finned fishes date to a common ancestor that lived about 420 million years ago, which had that torpedo-shaped, vaguely shark-like body plan (the Good Trick). Since they've been evolving for as long as have sharks, what have they done with that body plan since?

Like their chondrichthyan cousins, the ray-finned fishes have diversified into many different amazing forms, from millstone-like sunfish to gulper eels to sleek barracuda. And also like chondrichthyans, the basic shark-like body plan persists as a common "starting material" for most of these daring experiments in anatomy. Some ray-finned fishes alive today resemble the earliest members of this group, at least to the extent that some modern sharks resemble their ancestors.

And the lobe-finned fishes? Living coelacanths and lungfishes number only enough species to count on both hands, but like living sharks and rays they represent formerly much larger groups that also explored weird body plan variations. Still being aquatic, they've retained the same basic architecture of their ancestors. But what about the third member of this group, the tetrapods ("four-footed" beasts)? Some surviving members have changed relatively little over time despite their own extinct and experimental offshoots, and again these are typically aquatic or amphibious forms like salamanders. Where we see dramatic deviations from the ancestral body plan are in groups that have escaped the water and stumbled upon a new Good Trick. Among many examples are: flight, which evolved three separate times in tetrapods; new, faster ways of running in mammals and dinosaurs; and treetop leaping and swinging in many primates. Others came full circle and returned to the water, re-evolving shark-like body plans from very different starting material. The best example of these are not whales but rather the ichthyosaurs ("fish-lizards").


Ophthalmosaurus, a Jurassic ichthyosaur. Ichthyosaurs re-derived a shark-like body plan from a lizard-like ancestor. Image credit Nobu Tamura, from Wikimedia Commons.

Perhaps, someday in the far future, humble mice will be the only surviving members of what was once the most body-plan-diverse group of vertebrates, the mammals. Will some alien television narrator compare these mice to their tiny ancestors that once crept around Jurassic jungles? Might she remark, "My! How little they have changed...?"
-NA

Nested Sets of Sushi

This colorful opinion piece in Time by Josh Ozersky followed the 175-nation Convention on International Trade in Endangered Species (CITES); the outcome of which was, to be charitable, an unmitigated disaster for science-based fisheries management. At issue were US- and EU-backed proposals to ban trade in a number of marine species including sharks and bluefin tuna, which are being overfished vastly beyond the ability of these large, slow-growing fishes to replenish their populations.

It is difficult to deliberately fish a widespread, open-ocean species into extinction. The commercial inviability of continuing to target vanishing fishes will in most cases spare them from true extinction. Where these beasts can get in trouble is if they're hit by one or more extra liabilities: for example, going through a bottleneck in their life history where it's easy to find and fish them all up, or if they command exorbitant prices sufficient to keep fishing pressure intense to the point of complete stock exhaustion. The Atlantic bluefin tuna Thunnus thynnus bears both of these albatrosses. These voracious, silver leviathans can reach ten feet and 1400 pounds, taking decades to reach maturity. Populations are harvested wholesale when they gather in the Mediterranean, which is one of their exactly two spawning grounds. And to top it off, they are tasty. Very tasty.


Tuna being shaped at Tsukiji fish market, Tokyo.

The Japanese in particular are crazy about these things. A single, epic fish sold for $175,000 in Tokyo last year. It was no surprise that Japan spearheaded the effort to torpedo the proposed CITES ban on bluefin trade, along with a number of fishing nation allies including Canada, Indonesia, Venezuela, UAE and friends. The proposed ban was destroyed by a vote of 68 to 20, with 30 abstentions. That is a go-limping-home kind of whooping, crowned by a strident Libyan denunciation of sound fisheries science as "lies." Nice.

But this post isn't about conservation. It's about a curious twist in Mr Ozersky's mostly rational and impassioned call to boycott his once-beloved o-toro, bluefin sushi, in response to the shenanigans of Japan et al. Ozersky writes:

"It's been around for more than 400 million years, which means it is older than the trees, older than the Himalayas, older than the Atlantic Ocean itself. ... But either way, the loss of a creature that has been living here since before the continents formed won't be on my hands."

Wait. Huh?

Four hundred million years is old. Even in evolutionary time, this goes back to approaching the rise of large animal life on the planet. Paired fins and jaws had just made the scene. At this time near the beginning of the Devonian period, jawed fishes were finally getting their act together and beginning to diversify while their jawless cousins began a slow decline into obscurity. Most of these fishes were armored oddities called placoderms that have no living descendents. The first dinosaurs, lithe little things, wouldn't trod the earth for another 170 million years. So... is the Atlantic bluefin nearly twice as old as dinosaurs??

To answer this strange puzzle, let's consider the nature of life as a series of nested sets. This is the pattern of evolution by cladogenesis, in which an ancestral species gives rise over time to two distinct daughter species. This also has the nice consequence of producing a hierarchical arrangement of organisms. For example, all ferrets belong to a larger group called mustelids, along with weasels and sea otters and wolverines. All mustelids are placental mammals. All placental mammals are vertebrates, and all vertebrates are animals. Therefore, you don't predict to find weasels before mammals evolved, or mammals before the advent of animals.

Now how about tunas? Tunas are in a family of fishes called scombrids along with mackerels, bonitos, and other tasty things. They are nested well within the "set" of fishes called teleosts, which comprise over 99% of all living bony fishes, and the next larger group we'll worry about are the ray-finned fishes. So we can't have tunas without teleosts, we can't have teleosts without ray-finned fishes. Here's the problem.


Divergence times for groups containing bluefin tuna.

Teleosts, the crown group of bony fishes from marlins to mollies, date to the early Triassic period at the dawn of the dinosaurs, sometime around 240 million years ago (with some uncertainty). Right off the bat, we can see that there is no way that the bluefin can be older than that - you can't be your own grandpa, so to speak. What about ray-finned fishes? They crop up around 420 million years ago in the period right before the Devonian. Could this be what Ozersky meant? Even given that benefit of the doubt, does it matter? His heart is in the right place, but conservation may be legitimately justified by appealing to the maintenance of viable commercial markets, or ecosystems, or even an organism's aesthetic value (which I submit the bluefin has). Lemurs are worth protecting because they represent the entirety of a major offshoot of the primate family tree, not because they are vertebrates or animals or organisms with a discrete nucleus.

Species longevity is an interesting concept that gets at the heart of the pattern of "punctuated equilibrium" characterizing the fossil record of many groups. Punctuation is itself intriguing: why did this plant/animal/fungus' morphology change rapidly in a short period of time? But the equilibrium often gets lost in punctuation's spotlight: why do so many species not visibly change over long periods of time?

Across vertebrate taxa, species longevity tends to be on the order of only a few million years; perhaps 2-5. Even without knowing more about the timing of the scombrid fishes' radiation, we would not predict that the Atlantic bluefin is much older than that. The number of "famous" animals that buck the trend and appear to have changed very little over time can be counted on one hand, but are usually overblown. We'll return to the coelacanth, sharks, and similar cases in the next post, with a revelation or two that may surprise you.
-NA

Welcome to "This reView of Life"

The line with which Darwin closed On The Origin of Species captures much of why I am, why I always knew I would be, a biologist.

"There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

And as Darwin ended his transformative work, so begins this humble experiment in running commentary on science. I am inexhaustibly fascinated with and often appalled by the portrayal or synopses of science in the media, and hope to use this outlet to highlight interesting topics, redress wrongdoings, and expound upon loose ends in articles that come my way. I hope you will join me.