60 million years of global warming triggered the rise of reptiles: Harvard study

New York, August 20 Sixty million years of climate change triggered the meteoric rise of reptiles around 250 million years ago, not a mass mammalian extinction as previously thought, according to a new study by Harvard University.

Just over 250 million years ago, at the end of the Permian and the beginning of the Triassic, the rates of evolution and diversity of reptiles began to explode, resulting in a dizzying variety of abilities, body plans and of lines.

For a very long time, this bloom was explained by the fact that their competition was wiped out by two of the greatest mass extinction events (about 261 and 252 million years ago) in the history of the planet. .

Research by Harvard paleontologist Stephanie Pierce shows that the evolution and diversification seen in early reptiles not only began years before these mass extinction events, but was instead directly driven by what caused them. primarily caused by the increase in global temperatures due to climate change.

“Climate change has actually directly triggered the adaptive response of reptiles to help build this wide range of new body plans and the explosion of groups that we see in the Triassic,” said Tiago R. Simoes, postdoctoral fellow in the lab. Pierce and lead author. on the study.

In the paper, published in the journal Science Advances, the researchers took a close look at the evolution of a large group of organisms due to climate change, which is particularly relevant today as temperatures continue to rise.

In fact, the rate of carbon dioxide released into the atmosphere today is about nine times greater than it was during the period that culminated in the greatest mass extinction of all time due to climate change. climate, 252 million years ago: the Permian-Triassic mass extinction.

“Major changes in global temperature can have dramatic and variable impacts on biodiversity,” said Stephanie E. Pierce, curator of vertebrate paleontology at the Museum of Comparative Zoology.

The study involved nearly eight years of data collection as Simees traveled to more than 20 countries and more than 50 different museums to take scans and snapshots of more than 1,000 reptilian fossils.

The dataset showed that the rise in global temperatures, which began around 270 million years ago and lasted until at least 240 million years ago, was followed by body changes fast in most lineages of reptiles.

For example, some of the larger cold-blooded animals have evolved to become smaller so that they can cool themselves more easily; others have evolved to live in water for the same effect.

The smaller reptiles, which gave rise to the first lizards and tuataras, followed a different path than their larger reptile brethren, researchers have said.

Their rates of evolution have slowed and stabilized in response to rising temperatures.

This is because small-sized reptiles were already better adapted to the increasing heat since they can more easily shed heat from their bodies compared to large reptiles when temperatures rose very quickly all around the Earth.

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Teresa H. Sadler