Immobilized Caimans, Toxic Plants, and Alternative Theories – Dinosaur Exctinction Revived

Armed with the power of evolutionary theory, you can study and come to understand just about anything. Darwin was smart – but his genius resided not in his brain, but in his theory – which was even smarter than he was. The basic principles of evolutionary theory allow for an integrative and powerful lens to understand life – all aspects of life. This point resides at the core of the Evolutionary Studies (EvoS) Consortium, which is well on its way to revolutionizing higher education across continents (see Wilson, Geher, Waldo, & Chang, 2011). New research from Binghamton shows that EvoS students have a demonstrable intellectual edge over non-EvoS students – as a function of their EvoS education. In short, this research (to be published soon) shows that, as David Sloan Wilson puts it: EvoS makes you smarter.

At its core, EvoS has no tolerance for disciplinary boundaries. Constraining a research question within a micro-area of a traditional academic discipline is like trying to understand a car by being expert only in one section of the exhaust system. To really understand what’s going on, you need a big picture. And that’s what EvoS provides to students of all disciplines who come to the table with an open mind.

When it comes to applying evolution to a broad array of questions, Gordon Gallup of Albany may well take the cake. His research productivity has been nearly unmatched in the behavioral sciences since the 1960s. His research has addressed such disparate phenomena as self-recognition in non-humans (Gallup, 1970), the psychogenic effects of seminal fluid (Gallup, Burch, & Platek, 2002), the mating-relevant functions of the human voice (Hughes, Dispenza, & Gallup, 2004), reactions to children’s faces in the context of paternal certainty (Platek, Burch, Panyavin, Wasserman, & Gallup, 2002), and a lot more.

To say that Gordon is a productive scholar is an understatement. But what’s particularly noteworthy here is the breadth of topics covered in his work. One might wonder HOW someone could possibly be an expert on all these topics? How could someone who studies the chemical nature of seminal fluid be an expert also on the psychology of facial recognition? How are these studies interconnected?

To any EvoS student, the answer’s actually quite simple: These topics are all connected by the powerful and elegant principles found in evolutionary theory. Organisms that have come to typify species on our planet are products of evolution – they are filled with physical and behavioral adaptations that serve the purpose of reproductive success (or that served this purpose under ancient conditions for the organism’s ancestors).

Armed with a solid understanding of how to apply evolutionary principles, you really can study anything – and come up with new insights into old problems.

Consider, as Gordon has, the demise of the dinosaurs. As an evolutionist with a background in animal behavior, this is an issue that can readily be examined by someone with Gordon’s background. And yesterday, the community at SUNY New Paltz was fortunate to have Gordon present his ideas on this topic as part of our EvoS Seminar Series.

In a provocative and engaging manner, Gordon encouraged the audience to question the going explanation of dinosaur extinction put forth by Alvarez, Alvarez, Asaro, and Michel (1980) – oft-known as the “asteroid theory.” This theory essentially argues that a massive asteroid strike led to a “nuclear winter” and dramatic ecology alterations that ultimately led to the demise of dinosaurs, whose bodies were not able to deal with the resultant ecological changes.

If the asteroid theory is right, argues Gordon, dinosaur extinction should have probably taken place abruptly. Rather, the fossil record suggests that the extinction took more than 10 million years since the time of the asteroid impact.

Something else was likely going on. Here’s an alternative theory: Perhaps dinosaurs, notorious for having small brains, were not able to develop learned taste aversions to toxic plants. Plant toxins had evolved by the time of the dinosaurs – as a significant defense against herbivores. But, as Gordon points out, non-lethal plant toxins really only work if the animals who eat them learn to avoid them in the future. For this kind of learning to take place, a sufficiently advanced learning system must typify the animal. An animal that was not able to learn to avoid the same plant that had made it sick at a prior time might be eating at its own peril – eating volumes of plants that would otherwise be non-lethal in lethal amounts.

According to this theory, as toxin-producing plants proliferated, small-brained dinosaurs faced increasing selection pressures – and herbivores did not fare well – opening the doors for the demise of carnivores, who, of course, ate the herbivores.

Now this is a provocative theory!

But Gordon is known for collecting data – and he collected some pretty interesting data along these lines. Based on phylogenetic analyses, it turns out that caimans, small members of the crocodile family from South America, evolved directly from ancestors shared with the dinosaurs. Do caimans, under laboratory conditions, show learned food aversions? Are they smart enough to avoid eating something that made them sick last time? The answer is “not quite” – they seem to lack the learned-taste-aversion process that Gordon hypothesizes was lacking in herbivorous dinosaurs.

As if that’s not enough, Gordon, who’s spent his life around animals of various species, couldn’t help but test some other things about the caimans. You don’t run into a caiman every day! As a hobby, Gordon has an interest in tonic immobility – putting animals into a peaceful, hypnotic state by putting them in an immobile situation. He’s done this with chickens and cattle – and was apparently pretty curious – could he do it with a caiman? Apparently, the answer is YES – caiman are prone toward being put in a state of tonic immobilization (as Gordon’s slides made clear!).

Sure, that’s an aside, but a fun one. An aside that, I think, should get young scholars and researchers to see how genuinely fun and exciting research can be!

In the end, Gordon raised a lot of questions and made everyone think. And that’s what academia should be about! Are his data conclusive? Is the asteroid theory overblown? Can evolutionary psychology help us understand mass extinctions? These questions, and more, emerged as a function of this great EvoS presentation.

Missed Gordon’s talk? No worries – here’s the link to the streaming video!

(all EvoS talks, for the most part, are taped, permanently uploaded, and collected at – the world’s primary repository for evolution-related lectures).

And to end how I started: Armed with the power of evolutionary theory, you can study and come to understand just about anything. Many thanks to Gordon Gallup for explicating this point so well.


Alvarez, L. W., Alvarez, W., Asaro, F., & Michel, H. V. (1980). Extraterrestrial cause for the Cretaceous–Tertiary extinction. Science, 208, 1095–1108.

Gallup, G.G., Jr. (1970). Chimpanzees: Self Recognition. Science, 167, 86-87.

Gallup, G. G., Jr., Burch, R. L., & Platek, S. M. (2002). Does semen have antidepressant properties? Archives of Sexual Behavior, 31, 289-293.

Hughes, S.M., Dispenza, F., Gallup, G.G., Jr., (2004). Ratings of voice attractiveness predict sexual behavior and body configuration. Evolution and Human Behavior, 25, 295-304.

Platek, S.M., Burch, R.L., Panyavin, I.S., Wasserman, B.H., & Gallup, G.G., Jr. (2002). Reactions to children’s faces: Resemblance affects males more than females. Evolution and Human Behavior, 23, 159-166 .

Wilson, D. S., Geher, G., Waldo, J., & Chang, R. S. (2011). The EvoS Consortium: Catalyzing Evolutionary Training in Higher Education Introduction to this Special Issue Devoted to the EvoS Consortium. Evolution: Education, and Outreach, 4, 8-10.

Glenn Geher

About Glenn Geher

Glenn Geher is professor and chair of psychology at the State University of New York at New Paltz. In addition to teaching courses at both the undergraduate and graduate levels, and conducting research in various areas related to evolutionary psychology, Glenn directs the campus’ EvoS program, one of the most successful, noteworthy, and vibrant features of a campus that prides itself (rightfully) on academic vibrance. In Building Darwin’s Bridges, Glenn addresses the details of New Paltz’s EvoS program as well as issues tied to the future of evolutionary studies in the rocky and often unpredictable landscape of higher education.
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2 Responses to Immobilized Caimans, Toxic Plants, and Alternative Theories – Dinosaur Exctinction Revived

  1. Phyllis Freeman says:

    There is at least one on line report of attempting conditioned taste aversion in fresh water crocs. See:

  2. Phyllis Freeman says:

    I listened to the engaging talk from my old friend Gordon with a few questions that have me thinking about his talk even a day later.
    1. Why did he conclude that the failure to find one trial conditioned taste aversion (the Garcia effect) in the caiman implicated the same pattern for the dino? yes, both are from a common ancestor. But… Seemed like a bit of a stretch to me since caimans survived(and crocs and alligators) survived and dinos did not.
    2. Furthermore I do wonder about the control condition for the taste aversion training. The experimental group got chicken (supposedly a novel taste for this gp of animals) followed by an injection of apomorphine. The control animals just received the apomorphine. Both gps failed to develop conditioned taste aversion. But aren’t there a number of alternative explanations for this null finding (no taste aversion in either gp)? latent inhibition, for example from previous exposure to chicken (at the supply house- I assume not a likely explanation)? Too long a delay between the novel food and illness? (perhaps a lag of more than 30 minutes is too long for these creatures), Age of the caimans (they looked pretty small in the powerpoint and these very nasty creatures get huge and even nastier, and the little I know about these creatures is that they won’t feed if the temp is too hot and the crowd is too big around them.
    3. Lastly I wonder why didn’t Dr Gallup run one of the typical control gps for the Garcia effect?

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