Big skull proves tiny changes: Drimolen skull shows evidence for micro-evolution

Big skull proves tiny changes: Drimolen skull shows evidence for micro-evolution

Publishing Date: 11/11/2020 9:00 AM

Newly discovered fossil documents small-scale evolutionary changes in an extinct human species. Fossil cranium suggests environmental conditions drove rapid changes

Paranthropus robustus is a big toothed, extinct species of human ancestor from South Africa. Scientists believed that male P. robustus were much larger than females. A new fossil from Drimolen, South Africa suggests that P. robustus evolved rapidly because of climate change about 2 million years ago. This specimen shows the Drimolen P. robustus looks different to those from nearby Swartkrans.


Evolution within a species can be difficult to see in the fossil record. The record usually shows large patterns, like when species appear or go extinct. "The new male from Drimolen, DNH 155, gives us a chance to look at this species with a magnifying lens," says project co-director Stephanie Baker. Baker is from the Palaeo-Research Institute (P-RI) at the University of Johannesburg. The DNH 155 cranium is one of the best-preserved P. robustus specimens known to science.

"We discovered DNH 155 on Father's Day 2018. It is fitting that a big male was found on a day when we celebrate fatherhood," explains Baker. 

Screenshot 2020-11-11 at 10.12.57.jpgParanthropus are known for their huge teeth and thick skulls so that they could eat very hard foods. As the climate became drier and cooler, they were able to survive on less desirable food stuffs. They lived alongside early Homo. Homo, the species in our genus, are known for their adaptability. Their teeth were smaller since they were eating fruits and meat.

But this wasn't the case for the Drimolen Paranthropus. The position of their chewing muscles meant they couldn't chew with as much force as the later populations. That means that the population from Drimolen was not as well adapted to a dry landscape as the later Swartkrans population. We can say that in only 200 thousand years, this species was able to adapt to the climate.

Baker says "Drimolen is fast becoming a hotspot for early hominin discoveries".  The site has a very constrained date of 2.04 to 1.95 million years old. Earlier this year we announced the oldest Homo erectus in the world, DNH 134 or 'Simon'. This means there were three species of fossil human 2 million years ago. The Drimolen team, a group of specialists from around the world, hope to expand our understanding of early human evolution.

"It is important to know how these early species adapted to the changing climate. We ourselves are facing rapid climate changes. This study shows how detailed research can give us insight into ancient populations."


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Stephanie Baker, Co-director of research at the Drimolen Fossil Hominin Site in the Cradle of Humankind.