Just over 250 million years ago, during the end of the Permian period and the start of the Triassic, reptiles had one heck of a coming-out party.
Their numbers and rates of diversity surged, leading to a dizzying variety of abilities, body types, and traits and helping to firmly establish them as one of the most successful animal groups the Earth has ever seen. For years scientists attributed that success largely to luck: Two of the biggest mass-extinction events (around 261 and 252 million years ago) in the history of the planet wiped out much of their competition.
But a new Harvard-led study has added a second major factor to the reptile success story after tracing how the bodies of ancient reptiles evolved in ways that were evolutionarily advantageous amid millions of years of climate change. In fact Harvard paleontologist Stephanie E. Pierce’s lab found that the morphological evolution and diversification seen in early reptiles actually started years before the mass-extinction events took place and were driven by rising global temperatures.
“We are suggesting that we have two major factors at play — not just this open ecological opportunity that has always been thought by several scientists — but also something that nobody had previously come up with, which is that climate change actually directly triggered the adaptive response of reptiles to help build this vast array of new body plans and the explosion of groups that we see in the Triassic,” said Tiago R. Simões, a postdoctoral fellow in the Pierce lab and lead author on the study.
“Basically, [rising global temperatures] triggered all these different morphological experiments — some that worked quite well and survived for millions of years up to this day, and some others that basically vanished a few million years later,” Simões added.