The first primates evolved right after the dinosaurs died out

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A team of researchers announces that they have analyzed the oldest fossils of primates known to date. They were discovered in the Hell’s Creek Formation, Montana (United States). Details of the study are published in the journal Royal Society Open Science.

Analysis of the plesiadapiform mammals, a stem group from which all modern primates (including you) descend, is essential to understanding our evolutionary origins. With that in mind, we just took an incredible leap back.

The oldest primates

Paleontologists have recently isolated the remains (jaws and some teeth) of two specimens that lived between 105,000 and 139,000 years after the extinction of the Cretaceous-Paleogene which precipitated the disappearance of 75% of terrestrial life.

Prior to this discovery, the oldest evidence of stem primates in the fossil record dates back to the first 300,000 to 500,000 years of the Paleocene (the post-Mesozoic era). Gregory Wilson Mantilla, University of Washington, and Stephen Chester, City University of New York, initiated this study.

These two specimens represent two species named Janise Purifying and Purifying Mckeeveri. The first was already known to paleontologists, but P. mckeeveri (identified by three teeth) is a newly described species.

As part of this work, researchers examined fossils held at the University of California Paleontology Museum, which houses the largest collection of P. janisae remains. They also had epoxy casts of other Purgatorius fossils to work with, as well as enlarged 3D models. Finally, they relied on a technique called “geometric morphometry” to digitize and compare the characteristics of fossils to other known species.

According to paleontologists, the fact that two species evolved so soon after the Cretaceous-Paleogene mass extinction means that the ancestor of the plesiadapiformes appeared for the first time in the Upper Cretaceous, and not in the Paleocene.

High resolution scan of teeth and jawbones belonging to Purgatorius. Credit: Gregory Wilson Mantilla / Stephen Chester

An arboreal life

Nowadays, many primates can be distinguished by certain traits like the ability to grasp, jump, a herbal diet, improved vision, and a certain level of intelligence. However, we know from the fossil record that not all of these characteristics evolved at the same time.

In their time, the researchers point out that these two species were already enjoying a grasping ability (hands and feet) and dental features (specialized molars) allowing them to feed on fruits and insects. Also, the researchers point out that these animals lived most of their time in trees.

These characteristics, which therefore evolved very early in the evolution of primates, were essential to their evolution immediately after the disappearance of the dinosaurs “and within a million years after the mass extinction event“, Conclude the authors.

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