Understanding and Dating Primate Fossils

100 years of primate paleontology 

By: Richard F. Kay 

Summarized by Ethan Schimpf. Ethan Schimpf is a geology major at USF. He graduates in December of 2019. Upon graduation, he plans to move to Idaho and get a job in the mining field. During his free time he like hunting, fishing, and working on cars.

What data were used? 336 different primate species have been identified through the discovery of fossils as of 2017. Most of these fossils are found in North America and consists of jaws and teeth. 

Methods: This study used amino acid traces left in the fossils to date major changes in primate evolution, like when the split between New World Monkeys and Old World Monkeys occurred and when the split between humans and chimpanzees likely happened. 

Results: Some major traits used to differentiate the two major types (New and Old World) were the shape of the skull and the ability to walk on two legs. This major split occurred around 30 million years ago. With the advancement of technology over the past 100 years, humans are able to study fossils on the molecular and genetic level. The fossils are analyzed for changes in amino acid chains. This allows them to see the evolution of the DNA itself over time. Being able to witness this enables a more accurate timing to be assigned to major changes in primate evolution. In using this process, it was discovered that chimpanzees and humans shared a common ancestor about 5 million years ago. It was also discovered that the genetic molecular evolution rate would slow down as the species grew to a larger body mass as well as a larger brain size.

This graph shows the increase of fossils found within the last 100 years, starting with the first to be described, Adapsis, in 1821. With the abundance of fossils that have been found, scientists have been able to learn a lot more about the evolutionary history of the group that includes humans.

Why is this study important? Over the last 100 years the number of primate fossils being discovered has increased dramatically. The amount of primate fossils is still very low compared to other organisms and the quality of fossils is low. When putting together the evolution of primates through the fossil record, a major distinction was made between Old World Monkeys and New World Monkeys. The New World monkeys consist of shrew and lemur type primates, while the Old world Monkeys included groups like gorillas and chimpanzees. A later a common ancestor was found between humans and chimpanzees. This study allows us to date when major splits occurred during primate evolution. Through the examination of primate fossils major distinctions between common ancestor could be discovered and dated.

The big picture: The geographical distribution of different primates is thought to be due to the changes in sea level over time. At times of low sea level, land bridges formed and allowed primates to travel to different land masses. Then, when the sea levels rose,  primates became stuck in certain areas or separated from other populations of species. The timing of major primate evolution can be dated to similar times of higher seas when species were forced to remain in a particular area. This forced isolation resulted in the gain and loss of traits and, ultimately, new species forming. When dating the different primate fossils, changes in the DNA can be linked to major environment changes due to Earth’s changing climate.

Citation: Kay, Richard F. 100 years of primate paleontology. American journal of physical anthropology 165.4 (2018): 652-676.