Global Warming Spawned the Age of Reptiles

Harvard researchers find rapid evolution of reptiles was triggered by nearly 60 million years of global warming and climate change

Peer-Reviewed Publication



Studying climate change-induced mass extinctions in the deep geological past allows researchers to explore the impact of environmental crises on organismal evolution. One principal example is the Permian-Triassic climatic crises, a series of climatic shifts driven by global warming that occurred between the Middle Permian (265 million years ago) and Middle Triassic (230 million years ago). These climatic shifts caused two of the largest mass extinctions in the history of life at the end of the Permian, the first at 261myo and the other at 252myo, the latter eliminating 86% of all animal species worldwide.

The end-Permian extinctions are important not only because of their magnitude, but also because they mark the onset of a new era in the history of the planet when reptiles became the dominant group of vertebrate animals living on land. During the Permian, vertebrate faunas on land were dominated by synapsids, the ancestors of mammals. After the Permian extinctions, in the Triassic Period (252-200 million years ago), reptiles evolved at rapid rates, creating an explosion of reptile diversity. This expansion was key to the construction of modern ecosystems and many extinct ecosystems. These rapid rates of evolution and diversification were believed by most paleontologists to be due to the extinction of competitors allowing reptiles to take over new habitats and food resources that several synapsid groups had dominated before their extinction.

However, in a new study in Sciences Advances researchers in the Department of Organismic and Evolutionary Biology and the Museum of Comparative Zoology at Harvard University and collaborators reveal the rapid evolution and radiation of reptiles began much earlier, before the end of the Permian, in connection to the steadily increasing global temperatures through a long series of climatic changes that spanned almost 60 million years in the geological record.

“We found that these periods of rapid evolution of reptiles were intimately connected to increasing temperatures. Some groups changed really fast and some less fast, but nearly all reptiles were evolving much faster than they ever had before,” said lead author postdoctoral fellow Tiago R Simões.

Previous studies on the impacts of these changes have often neglected terrestrial vertebrates due to limited data availability, focusing mostly on the response from marine animals

In this study, Simões and senior author Professor Stephanie E. Pierce (both at Harvard) worked alongside collaborators Professor Michael Caldwell (University of Alberta, Canada) and Dr. Christian Kammerer (North Carolina Museum of Natural Sciences) to examine early amniotes, which represent the forerunners of all modern mammals, reptiles, birds, and their closest extinct relatives, at the initial phase of their evolution. At this point in time the first groups of reptiles and mammal ancestors were splitting from each other and evolving along their own separate evolutionary paths.

“Reptiles represent an ideal and rare terrestrial system to study this question as they have a relatively good fossil record and survived a series of climatic crises including the ones leading up to the largest extinction in the history of complex life, the Permian-Triassic mass extinction,” said Simões.

Reptiles were relatively rare during the Permian compared to mammalian ancestors. However, things took a major shift during the Triassic when reptiles underwent a  massive explosion in the number of species and morphological variety. This lead to the appearance of most of the major living groups of reptiles (crocodiles, lizards, turtles) and several groups that are now entirely extinct.

The researchers created a dataset based on extensive first-hand data collection of more than 1,000 fossil specimens from 125 species of reptiles, synapsids, and their closest relatives during approximately 140 million years before and after the Permian-Triassic extinction. They then analyzed the data to detect when these species first originated and how fast they were evolving using state-of-the-art analytical techniques such as Bayesian evolutionary analysis, which is also used to understand the evolution of viruses such as SARS-COVID 19. The researchers then combined the new dataset with global temperature data spanning several million years in the geological record to provide a broad overview of the animals’ major adaptive response towards climatic shifts.

“Our results reveal that periods of fast climatic shifts and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions,” said Pierce, “and this process started long before the Permian-Triassic extinction, since at least 270 million years ago, indicating that the diversification of reptile body plans was not triggered by the P-T extinction event as previously thought, but in fact started tens of million years before that.”

“One reptile lineage, the lepidosaurs, which gave rise to the first lizards and tuataras, veered in the opposite direction of most reptile groups and underwent a phase of very slow rates of change to their overall anatomy,” said Simões, “essentially, their body plans were constrained by natural selection, instead of going rogue and radically changing like most other reptiles at the time.” The researchers suggest this is due to pre-adaptations on their body size to better cope with high temperatures.

“The physiology of organisms is really dependent on their body size,” said Simões, “small-bodied reptiles can better exchange heat with their surrounding environment. The first lizards and tuataras were much smaller than other groups of reptiles, not that different from their modern relatives, and so they were better adapted to cope with drastic temperature changes. The much larger ancestors of crocodiles, turtles, and dinosaurs could not lose heat as easily and had to quickly change their bodies in order to adapt to the new environmental conditions.”

Simões, Pierce, and collaborators also mapped out how body size changed across geographical regions during this timeframe. They revealed that climatic pressures on body size were so high there was a maximum body size for reptiles to survive in tropical regions during the lethally hot periods of this time.

“Large-sized reptiles basically took two routes to deal with these climate shifts,” said Pierce, “they either migrated closer to temperate regions or invaded the aquatic world where they didn’t need to worry about overheating because water can absorb heat and maintain its temperature much better than air.”

“This strong association between rising temperatures in the geological past and a biological response by dramatically different groups of reptiles suggests climate change was a key factor in explaining the origin and the explosion of new reptile body plans during the latest Permian and Triassic,” said Simões.

The researchers would like to thank the Museum of Comparative Zoology (MCZ), Harvard University, vertebrate paleontology staff and the curators across 50+ natural history collections worldwide for their help with specimen access. Funding was provided by: Alexander Agassiz Postdoctoral Fellowship, MCZ; National Sciences and Engineering Research Council of Canada (NSERC) postdoctoral fellowship; Grant KA 4133/1-1 from the Deutsche Forschungsgemeinschaft; NSERC Discovery Grant #23458 and NSERC Accelerator Grant; Faculty of Science, Chairs Research Allowance, University of Alberta; Lemann Brazil Research Fund; Funds made available through Harvard University.



Science Advances




Successive climate crises in the deep past drove the early evolution and radiation of reptiles



From EurekAlert!

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Ron Long
August 19, 2022 6:11 pm

Here we go again. The Modern Warm Period is giving rise to reptiles again, especially snakes and lizards, who dress up like normal humans, intending to avoid detection, but given away by their embracing CAGW Looney Nonsense. We may have to wait for the next glacial cycle to solve the problem.

Joao Martins
Reply to  Ron Long
August 20, 2022 1:13 pm

You arrived first: I was going to write a very similar comment, asking if we need to wait some thousand years to have Climate Change produce rational humans again… Harvard used to be a good school…

August 19, 2022 6:14 pm

Ah ha. Global warming and increasing CO2 are indeed good for life on earth. #CelebrateCO2.

Reply to  John Shewchuk
August 20, 2022 9:28 pm

Exactly!! It seems to me they forgot to mention it was the extreme COLD of the Permian extinction (Ice Ball Earth iirc is the term the paleontologists like to use) that derailed the mammals – actually, check that – that nearly wiped out all life on this planet, made the Cretaceous extinction look like a slip in the bathtub. When what shred of life managed to hang on and the warmth return, that increasing warmth lead to the most beautiful and terrible biosphere with creatures and plant life filling the world from pole to pole and everywhere in between and around. Makes our cold world look like a dry, cold desert in comparison – because that’s what it is. If the green nuts get their way this world would go back to the cold of 300-400 years ago, or worse if they succeed in carbon capture schemes the removal of significant amounts of co2.

Reply to  PCman999
August 21, 2022 4:55 am

Correct — and we are in a CO2 famine …

Gary K Hoffman
Reply to  PCman999
August 21, 2022 8:14 am

I thought that Snow Ball Earth preceded the Permian, by several hundred millions of years.

August 19, 2022 6:26 pm

Is this relevant to global warming in the 21st century?

August 19, 2022 6:59 pm

It’s a plug for evolution.

August 19, 2022 7:14 pm

I, for one, will welcome our new reptilian overlords.

They have got to be better than the current bunch running our governments.

Reply to  H.R.
August 19, 2022 7:29 pm

I don’t think we’d see much of a difference seeing that both only have reptilian brains.
Or in the case of Biden, a senile reptilian brain – vicious and self serving but forgetting why.

Richard (the cynical one)
Reply to  Brad-DXT
August 19, 2022 10:20 pm

As opposed to a Marelagosaurus reptilian brain, also vicious and self serving, and never forgetting why.

Reply to  Richard (the cynical one)
August 19, 2022 11:01 pm

Good thing we sent thirty armed agents to check the Marelagaosaurus for keeping some documents. Or flushing documents down the toilet. Or nuclear secrets. Or being an agent of Saudi Arabia (by the way, what were the Saudis getting for their oil prior to Jan 2021?). Or hiding North Korean notes on napkins, apparently in Mrs. Marelagaosuarus’s wardrobe.

Gary Pearse
Reply to  anthropic
August 20, 2022 9:01 am

Nancy Palosiosaurus is a green marine dinosaur.

Here she is swimming

comment image

Gary Pearse
Reply to  Gary Pearse
August 20, 2022 9:03 am

comment image

Reply to  Gary Pearse
August 20, 2022 9:17 pm

Thank God you didn’t actually post a picture of her swimming! Oh the nightmares that would have caused!

Reply to  PCman999
August 21, 2022 8:38 am

That is her … without the spackle and lipstick she looks different.

Reply to  anthropic
August 20, 2022 9:07 am

Mrs. Marelagaosuarus’s wardrobe was searched just to sniff and possibly hand off to “the Big Guy”.

I think she is hot. Yeah, I’m old.

Dave Fair
Reply to  Brad-DXT
August 20, 2022 1:40 pm

She’s hot, no matter your age.

Shoki Kaneda
August 19, 2022 7:20 pm

Did dinosaurs have Suburbans?

Reply to  Shoki Kaneda
August 19, 2022 7:46 pm

Heck, no, Shoki. They all drove EVs and just look what happened, runaway global warming. Politicians take note.

John Tillman
Reply to  Shoki Kaneda
August 19, 2022 7:50 pm

No, but the methane released by sauropods might well knock out modern humans.

Reply to  Shoki Kaneda
August 20, 2022 3:21 pm

Jet fighters and cheap air travel. AFAIK. 😎

Walter Sobchak
August 19, 2022 7:33 pm

Fun with numbers. So what.

Richard Page
Reply to  Walter Sobchak
August 20, 2022 1:29 pm

Absence of significant numbers – they are very, very keen to omit things like varying oxygen levels in their theory; obviously nothing else must intrude into the ‘climate change’ narrative!

Smart Rock
August 19, 2022 7:39 pm

Our results reveal that periods of fast climatic shifts ….. are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions

Stating the blindingly obvious and boldly claiming that they discovered it.

Surviving Pleistocene glaciations by rapid adaption is what made us, as a species, capable of developing the internet (among other achievements). Future historians can debate whether this was a good thing or not.

Reply to  Smart Rock
August 19, 2022 9:21 pm

Future paleontologists more likely! lol

Coach Springer
Reply to  Smart Rock
August 20, 2022 7:24 am
August 19, 2022 7:48 pm

Whilst they seem intent on tying temperature to the evolution of the reptiles, given all life forms as we know now are carbon based, I assume all earlier ones were too, and given we also know how the CO2 levels in the atmosphere are directly related to plant growth, I am surprised that they haven’t made the same CO2 connection for those early reptiles.

CD in Wisconsin
August 19, 2022 7:52 pm

“One principal example is the Permian-Triassic climatic crises, a series of climatic shifts driven by global warming that occurred between the Middle Permian (265 million years ago) and Middle Triassic (230 million years ago).”


So now natural drivers of climate cause climate crises too? Now I’ve heard it all. 

Reply to  CD in Wisconsin
August 20, 2022 11:37 am

Nah, there must have been an ancient civilization that drove too many SUVs and heated with coal.

August 19, 2022 7:56 pm

What do the terms “fast”, “rapid” mean in this article? A million years?

Why does any article that contains the term “climate” have to sound breathless and hysterical even when it is discussing evolution on a millions of years time scale.

August 19, 2022 7:57 pm

Harvard used to be amongst the pinnacles of education…

Now, they’re rapidly following the dinosaurs.

Our results reveal that periods of fast climatic shifts and global warming are associated with exceptionally high rates of anatomical change in most groups of reptiles as they adapted to new environmental conditions,” said Pierce”

And Harvard found high resolution records to track “exceptionally high rates of anatomical change”?


“We found that these periods of rapid evolution of reptiles were intimately connected to increasing temperatures. Some groups changed really fast and some less fast, but nearly all reptiles were evolving much faster than they ever had before,” said lead author postdoctoral fellow Tiago R Simões.”

Isn’t that just a sound scientific statement? “faster than they ever had before”…

Reply to  ATheoK
August 19, 2022 10:47 pm

Along with “really fast”.

Reply to  Retired_Engineer_Jim
August 20, 2022 12:20 am

And ”less fast”.

Reply to  ATheoK
August 20, 2022 12:24 am

Hey! I’ll have you know this was peer reviewed thank you very much!

August 19, 2022 8:08 pm

Non-bird dinosaurs lived between about 245 and 66 million years ago, in a time known as the Mesozoic Era. This was many millions of years before the first modern humans, Homo sapiens, appeared. Scientists divide the Mesozoic Era into three periods: the Triassic, Jurassic and Cretaceous.

Until about 215 million years ago, the Triassic period had experienced extremely high CO2 levels, at around 4,000 parts per million — about 10 times higher than today. But between 215 and 212 million years ago, the CO2 concentration halved, dropping to about 2,000ppm.

What were CO2 levels in the Jurassic period?
CO2 concentration in the range of ~ 750–975 ppm was calibrated from the fossil material, with a best-estimated mean of ~ 900 ppm.

Michael ElliottMichael Elliott
Reply to  Richard Greene
August 19, 2022 8:24 pm

When they refer to rapid change, they are talking about millions of years, not a few hundred from the peak of the Little Ice Age.

As for that small increase in temperature of one Celsius, so what.

It’s all cycles, warmer, colder, wetter, dryer.

As real science has been silenced, we will just have to wait until the lights start to go out.

Michael VK5ELL

Richard Page
Reply to  Richard Greene
August 20, 2022 1:39 pm

Possibly the wrong question. Now if you’d asked about the Oxygen concentrations and linked that to possible CO2 concentrations it might be interesting. Oxygen was around 30% in the Permian era, dropping to somewhere around 10-15% in the late Permian/early Triassic, rising to roughly 20-21%, somewhere near todays value, by the late Triassic. I’m guessing that the fluctuations in Oxygen and CO2 may be linked.

Reply to  Richard Page
August 20, 2022 9:35 pm

Are you sure about that? There were still large insects in existence in the late Cretaceous that would have suffocated in today’s low concentration. O2 % must have been in the 30’s all through the T-J-C period.

August 19, 2022 8:10 pm

But, I thought Earth’s climate was perfect until the first coal fired power plant came on line.

Reply to  Alan
August 20, 2022 3:22 pm

First steam engine. Much earlier. Damned Cornish!

Mike Lowe
August 19, 2022 9:36 pm

Haven’t we heard somewhere that “Correlation is not proof of Causation”? Isn’t my guess as good as theirs?

Reply to  Mike Lowe
August 20, 2022 1:04 am

I’m reminded of a woke argument that HV power lines “cause” cancer in children. Data offered in support was the number of cancer cases within 300m of HV lines. Someone pointed out that many of these lines went through low socio-economic areas particularly in the built-up areas because building them is less opposed and they have lower land acquisition costs. Ah yes – maybe other causes contribute within 300m of HV lines, You know like smoking, poor health services, poverty stress, poor nutrition, dangerous jobs, etc. So Correlation not necessarily Causation. But within 20m might have been a completely different thing if only they had the data. Max: missed it by that much.

Johne Morton
August 19, 2022 9:59 pm

This whole bit is confusing. They’re talking about “rapid” climate changes occurring over millions of years as the continents slowly moved and mountain ranges came and went over eons. Meanwhile, we’ve had the lightning-fast changes since the beginning of the Pleistocene and no mass extinctions until some guys with bearskins, spears, and modern dogs showed up…

Reply to  Johne Morton
August 20, 2022 3:25 pm

What mass extinctions? The Dodo and the passenger pigeon. Two species.

Johne Morton
Reply to  Chaswarnertoo
August 21, 2022 5:23 pm

Wooly mammoth, mastodon, dire wolf etc. The ice age megafauna. We, and probably with the help of newly domesticated man’s best friend, did that.

Brian Pratt
August 19, 2022 10:10 pm

I have a hard time believing the elevated sea surface temperatures claimed for the Lower and Middle Triassic. Ref. 47 doesn’t look all that reliable to me, and I confess to not having checked the S1 data file. In any case, lumping the whole story together and crunching the numbers without the specific geological context of each locality is obviously bound to be misleading. There is so much of this sort of thing.

Philip CM
August 19, 2022 10:22 pm

Scientists are now offering opinions as scientific theory. Enjoy the era of fake science… right alongside of fake news. Progress! 🤔🤷‍♂️

Mike Dubrasich
August 19, 2022 11:13 pm

Following the Carboniferous-Permian Ice House climate, the Earth warmed ~265 million years ago (see this chart from WUWT Reference Pages – Paleoclimate here).

comment image

For the next ~263 million years the Earth was warmer than today — as much as 16°C warmer and averaging ~8°C warmer. That’s a long time, more than a quarter of a billion years. A lot happened: dinosaurs, mammals, birds, flowering plants, etc. The normative temperature of the planet was much warmer than today for all that evolution.

Only recently, in the last 1.8 million years, came our Ice Age, one of the coldest eras in geologic history. It’s really chilly, comparatively.

One might speculate, if one were so inclined, that Gaia invented humans (the only creatures that make fire) to warm up the planet. Gaia likes it warm. She doesn’t like Icy Earth. It’s not normal for the planet to be this cold.

Warmer Is Better. Fight The Ice.

NB: I intended to use the Edit Function for the lengthy link, but it isn’t working at this moment, for me, I don’t know why.

Old Man Winter
Reply to  Mike Dubrasich
August 20, 2022 2:36 am

I use Firefox & there are random times it will disappear my post & only show
the cancel & save buttons after I use the “edit” feature. I reload the page & it
then works normally. I don’t remember reloading not doing the trick. Anyone
else have a better way to fix the problem?

BTW, great comment! We’ve been enduring Quarternary glaciation
for ~2.5M yrs where we alternate between ice ages & interglacials. Brrrrrr! It’s freezing!

John Tillman
Reply to  Mike Dubrasich
August 20, 2022 2:30 pm

Your Phanerozoic temperature curve shows the PETM cooler than the Cretaceous. Most reconstructions have it at least as warm as the mid-Cretaceous Hot House. Scotese makes it two degrees C hotter, ie 26 v. 24.

Reply to  Mike Dubrasich
August 20, 2022 9:43 pm

Gaia invented us to put back the CO2 in the air, yes, but primarily to swat the next planet killing asteroid – she misses her dinos so much and certainly wouldn’t want the same fate to happen to pandas and koalas. Or us, for that matter.

August 20, 2022 12:22 am

Peer reviewed, meaningless speculation. Very good.

August 20, 2022 3:37 am

Well at least it is nice to see a paper that does not blame warming on what the “consensus” now has determined is the most powerful molecule on earth.

August 20, 2022 3:54 am

60 million years. Is that a trend or a wave? Inquiring minds and whatnot. 🤣

Rainer Facius
August 20, 2022 5:35 am


According to Scotese, atmospheric CO2 concentrations during the Permian and the initial Triassic period were at an all-time low, second only to that in the Pliocene to most of the Quaternary epoch, where it was lower by a factor of 2. Nevertheless, the dramatic Permian rise in temperatures by nearly 10K ( TEN! in words ) took place during the significant – more or less constant – CO2-deprivation since the late Carboniferous period, in comparison to the preceding 300 Mio. years.
Final ‘proof’ that only manmade CO2 is bad and drives the biosphere to extinction.
BTW, CO2 concentrations and Temperature were anti-correlated during most of the Cretacious – but again, that holds only for natural CO2.

August 20, 2022 6:47 am

We’re there cars and industry back then??? Must be dinosaur farts.

Gary Pearse
August 20, 2022 8:51 am

This is the messiest of scientific reports. They really haven’t discovered anything. They have underscored that warmth and high CO2 are exceptionally important factors in promoting life and biodiversity. I studied this in paleontology in the 1950s. The warmth certainly wasn’t a “crisis” and it was not anybody’s “fault”

The Great Greening Miracle is a modern proof that even modest increases in warming and CO2 are powerful life forces. It shows also, that at current levels the biosphere is hungry for more.

Reply to  Gary Pearse
August 20, 2022 3:27 pm

Sadly, even burning all available fossil fuel will not get us to the ideal 1000ppm.

Christopher Chantrill
August 20, 2022 11:59 am

“60 million years of global warming and climate change”

The Horror.

August 20, 2022 3:39 pm

Oh. Harvard. Yeah, right. Like there are any credible “scientists” at that institution.
I don’t think so.

August 20, 2022 4:20 pm

So what’s their point? Global warming now will make reptiles take over again? One look at Klaus Schwab and – maybe they’re right 😬

Paul Hurley (aka PaulH)
August 21, 2022 7:47 am

Maybe global warming will mean I’ll finally have a pet dinosaur!

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