This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
When I was a child, I wanted a pet dinosaur. If I’m at all honest, I still do, and I don’t mean a budgie or an emu. I wanted a Brontosaurus of my very own to ride to school, her long neck angled through the windows in the warmer months so that I could feed her leafy treats during the day. (I hadn’t given much thought to how a sauropod would handle icy New Jersey winters.) But I knew this could never be. Every dinosaur book I devoured in school and public libraries was crystal clear that dinosaurs were totally, irrevocably extinct, and there were about as many ideas about their demise as there were paleontologists.
The books I read were almost all out of date, the libraries not exactly keeping up with the burgeoning Dinosaur Renaissance, and by the time I was reading them paleontologists were still fiercely debating whether or not an asteroid strike could have caused the mass extinction at the end of the Cretaceous. The answer, in part if not in whole, turned out to be “Yes.” The devastation caused by an extraterrestrial chunk of rock has time and again been underscored as the deciding factor in why the non-avian dinosaurs were erased from Earth’s faunal list, even if precisely how
the minutes, hours, days, weeks, months, and years after the impact are still being discussed.
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This hasn’t stopped a pair of outside experts from proposing a weird idea to explain the death of our favorite dinosaurs.
“The demise of dinosaurs and learned taste aversions: The biotic revenge hypothesis” is a paper that could very well have come out in 1978. That time is what paleontologist Michael Benton terms the “Dilettante Phase” of dinosaur extinction theorizing, when just about any academic with half an idea and some spare time could publish their peculiar view of what happened to the dinosaurs. This was the time when cataracts, slipped discs, egg-eating mammals, and hungry, hungry caterpillars were all implicated in one way or another, potentially tipping the dinosaurs into extinction but not explaining the rest of the biodiversity plummet - including pterosaurs, ammonites, reef-building clams, and more - roundabout 66 million years ago.
The new paper, by Michael Frederick and Gordon Gallup, Jr., would fit right in with those discarded ideas. Here’s how it goes. Plants have always been in an evolutionary arms race with the animals that eat them, throwing up all sorts of defenses through evolutionary time. This includes toxins that cause stomach aches, Frederick and Gallup, Jr. write, which causes modern animals to avoid those plants or foods they associate with them. But what if dinosaurs were incapable of learning which plants would make them ill? If this were the case, Frederick and Gallup, Jr., propose, then herbivorous dinosaurs would have been in a terrible state of gastric distress when the asteroid struck and somehow made them more vulnerable to extinction.
There’s no evidence to support this.
We don’t know which plants were toxic to dinosaurs, or how those plants would have affected them. Frederick and Gallup, Jr. propose that there must have been toxic angiosperms that cramped dinosaur bowels, and perhaps that was so, but there’s no direct evidence of such a reaction. (Not to mention that conifers can contain toxins, as well, and were being munched on by dinosaurs for far longer than flowering plants.) Instead Frederick and Gallup, Jr. claim that dinosaurs were in decline for about 10 million years before the asteroid strike, arguing that increasing plant toxicity could explain this. The problem is that dinosaurs were still going strong at the end of the Cretaceous, and a coordinated, synchronous, planet-wide decline across species, families, and continents requires some pretty solid evidence to back. There is none.
So Frederick and Gallup, Jr. did something weird to drum up support for their claim. Mistakenly casting caimans are representative of dinosaur ancestors, they created a study sample of 10 of the crocodylians split into two groups. One was given a sickness-inducing shot in association with being fed chicken, and the other group just got the shot with their regular diet. (Apparently there was no control group.) Neither seemed to show any food aversions despite being made sick. Frederick and Gallup, Jr., take this as a scientific victory, proof that dinosaurs would not have been able to learn taste aversions - all despite the fact that we know avian dinosaurs can learn to avoid sickness-inducing foods, plus the fact that caimans are carnivores and not that closely related to dinosaurs. They call this the plant’s “biotic revenge,” although it’s hard to see how that title fits when the entire idea was that dinosaurs were too careless or unaware to get the signals plants were sending them.
I checked the paper more than once to make sure it wasn’t released on April 1st. And Michael Frederick really is listed as a psychologist at the University of Baltimore, with Gordon Gallup, Jr. listed as an evolutionary psychologist at University of Albany. The official press release I got in my inbox only further had me scratching my head as to whether this is a real proposal or a hoax to see if news outlets or other researchers would run with it.
The truth is that we still have a lot to learn about why the non-avian dinosaurs went extinct. Why I can’t saddle up a sauropod today. Perhaps it’s as simple as the devastation unleashed by the asteroid strike was too much for the non-avian dinosaurs to survive. Even lineages that made it through took heavy losses, after all. And perhaps the strike caught dinosaurs at a time of transition, changes in sea level and the effects of massive volcanic eruptions in paleoIndia putting various species under pressure. There’s even been some ecological work suggesting that a life shifted to eating seeds might have allowed toothless birds to survive while more carnivorous toothed birds and non-avian dinosaurs perished. The last word on the end of the Cretaceous has yet to be written.
But the biotic revenge hypothesis winds up as nothing more than selective speculation, not to mention the concerning fact that the paper has no information on the ethical standards and supervision of making captive caimans sick. There’s not even much of a connection between the dinosaurian GI tract disorders and their ultimate demise. The herbivorous dinosaurs were sick, and therefore more likely to die in the hot-cold blasts of the impact’s aftermath, the argument goes, but this is like saying someone had a bit of a stomach flu the day before getting stabbed. Nor does the hypothesis explain anything about the mass extinction or any of the other affected groups. Dinosaurs bring out the weird ideas because they’ll get more media play than rudist clams or the last plesiosaurs, so at most the dinosaur tummyache hypothesis can just be added to the long list of fringe speculation that has surrounded one of the all time worst days in Earth history.