Still believe an asteroid killed the dinosaurs? Think again—new theory suggests

April 4, 2018, University at Albany
Still believe an asteroid killed the dinosaurs? Think again--new theory suggests
Psychology professor Gordon Gallup (left) and his former student Michael Frederick (right) claim that due to a psychological deficit, the dinosaurs were dying off long before the notorious asteroid hit.  Credit: University at Albany

Some experts have long believed that a massive asteroid was a primary cause of dinosaurs' extinction some 65 million years ago, but new analysis from a University at Albany psychology professor suggests that the dinosaurs were in trouble long before the asteroid hit.

Professor and evolutionary psychologist Gordon Gallup and his former student Michael J. Frederick, now of the University of Baltimore, assert that the emergence of toxic combined with dinosaurs' inability to associate the of certain foods with danger had them already drastically decreasing in population when the asteroid hit.

"Learned taste aversion" is an evolutional defense seen in many species, in which the animal learns to associate the consumption of a plant or other food with negative consequences, such as feeling ill. To explain the defense mechanism, Gallup offers the example of rats.

"A reason why most attempts to eliminate rats have not been successful is because they, like many other species, have evolved to cope with plant toxicity," said Gallup. "When rats encounter a new food, they typically sample only a small amount; and if they get sick, they show a remarkable ability to avoid that food again because they associate the taste and smell of it with the negative reaction."

The first flowering plants, called angiosperms, appear in the fossil record well before the asteroid impact and right before the dinosaurs began to gradually disappear. Gallup and Frederick claim that as plants were evolving and developing toxic defenses, dinosaurs continued eating them despite gastrointestinal distress. Although there is uncertainty about exactly when flowering plants developed toxicity and exactly how long it took them to proliferate, Gallup and Frederick note that their appearance coincides with the gradual disappearance of dinosaurs.

In addition to studying the proliferation of while dinosaurs were alive, Gallup and Frederick examined whether or not birds (considered to be a descendant of dinosaurs) and crocodilians (also considered to be descended from dinosaurs) could develop taste aversions. They found that the birds, rather than forming aversions to taste, developed aversions to the visual features of whatever made them sick. Still, they knew what they shouldn't eat in order to survive. In a previous study in which 10 crocodilians were fed different types of meat, some slightly toxic, Gallup discovered that like dinosaurs, crocodilians did not develop learned taste aversions.

"Though the asteroid certainly played a factor, the psychological deficit which rendered dinosaurs incapable of learning to refrain from eating certain plants had already placed severe strain on the species," said Gallup. "The prevailing view of dinosaur extinction based on the asteroid impact implies that the disappearance of should have been sudden and the effects should have been widespread, but the evidence clearly shows just the opposite: Dinosaurs began to disappear long before the and continued to gradually disappear for millions of years afterward."

The full paper is published in the peer-reviewed Ideas in Ecology and Evolution.

Explore further: Dinosaurs were 'too successful for their own good'

More information: The demise of dinosaurs and learned taste aversions: The biotic revenge hypothesis: ojs.library.queensu.ca/index.p … EE/article/view/6802

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Jonseer
1 / 5 (5) Apr 04, 2018
When will they discover the truth that it was militant lesbianism that killed off the dinosaurs.

Just before the meteor hit, female dinos united in their deep loathing for the males of their various specious decided they would never let any of them procreate with them again. Instead they opted for a conscious effort to force the development of parthenogenetic form of reproduction which would males unnecessary.

On the cusp of success lesbianasaurs across the world were called to and attended massive, female born only conclaves to announce the news that females would be able to reproduce at will on their own.

As fate would have it just as the last speaker was winding up her speech the meteor struck.

The fact that almost all female dinos were in a few locations packed together at the conclaves
close to the strike meant the vast majority of female dinos were the first to die ensuring the extinction of all of them. ;-)
humy
3.3 / 5 (3) Apr 05, 2018
There are things wrong with this theory (not the above posted 'militant lesbianism' one but the 'toxic plants' one from the article).
Many toxic plants must have inevitably evolved in response to millions of years of insect and millepede attack, which were a problem for plants LONG before the first dinosaurs which came MUCH later. This is because it often only take one mutation in a plant for it to produce a new and protective toxin and there is no 'barrier' preventing such a mutation from occurring.
So that means plenty of time for the smaller fast-evolving ancestors of dinosaurs to evolve to respond to toxic plants by stop eating them and there is no 'barrier' preventing that evolution from happening.
antialias_physorg
1 / 5 (1) Apr 05, 2018
OK, I don't quite buy this theory. Even when a certain plant develops a toxicity it doesn't replace all those plants overnight. Much less all other plants (such mutations don't just magically transfer over to other species. Yes, there are cross cutting vectors such as bacteria and viruses which can effect a gene transfer, but that is no way effective enough to make a mutation in one plant suddenly proliferate in all plant types that serve as a food source).

Moreover such a toxicity is a very potent selection agent in the dinosaur population. There should have been rapid adaptation (as opposed to the learned aversion, which they rightly pointed out can be duped). Certainly not a weakness that persisted for "millions of years" without having any selection effect whatsoever.
Nik_2213
5 / 5 (1) Apr 05, 2018
Perhaps it was the 'Large Igneous Province' pumping out inorganic toxins, which then accumulated in the food chain ??
dustywells
4 / 5 (1) Apr 05, 2018
The toxin need not be a fatal poison. It could be as addictive as sugar but result in a reduction of fertility while the feces would help to spread the seeds.
gculpex
3 / 5 (2) Apr 05, 2018
The toxin need not be a fatal poison. It could be as addictive as sugar but result in a reduction of fertility while the feces would help to spread the seeds.

Like apples are...
rrwillsj
1 / 5 (1) Apr 05, 2018
Clickbait headlines contradicted by some of the conclusions within the article. Though the remainder were vague enough to sustain the hypothesis.

What I take away from this type of writing? Is a healthy boost to my innate skepticism. For instance, crocodiles are reptiles not dinosaurs.

Previous research described the species we lump together as dinosaurs in a cycle of retrenchment before the K2 Event. Instead of a hundred different types of exotic families differentiated by local adaption to an assortment of ecological niches? With a stable environment, diversification became unnecessary. Over all population density remained constant, just with fewer varieties of dinosaurs.

I suppose it was possible that smaller dinosaurs consumed flowers? Is that evidenced in their corprolite?

Today, it is leaves that gain toxicity during the growth cycle. That's why color vision. Pale red shoots of leaves? Yummy good. Later in season, dark green? Yucky, bad!

antialias_physorg
not rated yet Apr 05, 2018
The toxin need not be a fatal poison. It could be as addictive as sugar but result in a reduction of fertility while the feces would help to spread the seeds.

That would still constitute a selective agent. Dinosaurs that are less prone to the addictive component would quickly outbreed the ones that are. Drugs don't work the same on every member of a species (heck, some people get drunk easily others hardly at all)
grandpa
1 / 5 (2) Apr 06, 2018
I have to believe that birds spread pathogens at too fast a rate for the dinosaurs to survive.
humy
4 / 5 (1) Apr 06, 2018
I have to believe that birds spread pathogens at too fast a rate for the dinosaurs to survive.

would that mean elephants also wouldn't survive?
Da Schneib
not rated yet Apr 06, 2018
Hmmm, I'd want to see more on how long it took the big dinosaurs to die off. Quite a few species are present before the impact signs and absent after them; it's pretty well established that there was a mass extinction at that time.
katesisco
1 / 5 (1) Apr 06, 2018
I am waiting for the Delphi Oracle to pronounce the demise as being toxic earth gases.
James_Mooney
not rated yet Apr 06, 2018
I think tiny, fast mammals that loved eggs just raided the lumbering dinosaurs nests and ate them to extinction.
humy
not rated yet Apr 07, 2018
I think tiny, fast mammals that loved eggs just raided the lumbering dinosaurs nests and ate them to extinction.

the strong shells of the huge dinosaur eggs would have given them some protection against small mammals which would have found it difficult to bite through the thick shells just like modern mice cannot bite through the thick shells of ostrich eggs.

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