Biologists establish the origin date of the earliest tetrapods and discover they acquired several of the major new adaptive traits that enabled vertebrate life on land at accelerated evolutionary rates.

In a study published August 23 in Nature Ecology and Evolution Harvard researchers establish the origin date of the earliest tetrapods and discover they acquired several of the major new adaptive traits that enabled vertebrate life on land at accelerated evolutionary rates.

The study led by Dr. Tiago R. Simoes, postdoctoral researcher, and senior author Professor Stephanie E. Pierce, both from the Department of Organismic and Evolutionary Biology, Harvard University, applied recently developed statistical methods (Bayesian evolutionary analysis) to precisely estimate the time and rates of anatomical evolution during the rise of tetrapods. The Bayesian method was adapted from methods originally developed in epidemiology to study how viruses like COVID-19 evolve and only recently became a tool in paleontology for the study of species evolution.

The study also innovates by combining data from fossil footprints and body fossils to pinpoint the time of origin of the tetrapods. «Normally footprint data shows up after body fossils of their track makers. In this case, we have tetrapod footprints much older than the first body fossils by several million years, which is extremely unusual. By combining both footprint and body fossils, we could search for a more precise age for the rise of tetrapods,» said Pierce.

«We were able to provide a very precise age for the origin of tetrapods at approximately 390 million years ago, 15 million years older than the oldest tetrapod body fossil,» said Simoes.

The researchers also found that most of the close relatives to tetrapods had exceptionally slow rates of anatomical evolution, suggesting the fish relatives to tetrapods were quite well adapted to their aquatic lifestyle.

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