Know Your Hominid Skulls
As scientists work to identify and catalog the now more than 800 hominid fossils recovered on the Rising Star Expedition, they pull from a body of knowledge accumulated over decades in their field.
An intimate knowledge not only of broad principles but of specific specimens around the world is their constant reference as each piece is brought to the tent marked “SCIENCE.”
While it’s entirely possible that somewhere in the cave below, hidden under dirt and other bones lies a perfectly intact skull, so far the the team is working with pieces brought up individually and carefully fitted together by Peter Schmid, an expert in reconstructions who gave Lucy her more accurate reassembly in the 1980s.
Peter was aided in his skull work last week by Darryl de Ruiter of Texas A&M University, who carefully examined every skull fragment and individual tooth in-hand and under a powerful digital microscope. At either scale, he looks for specific traits that when taken together help identify the species behind the pieces.
Here in South Africa, there are four main hominid species that have been discovered. The following sketches attempt to illustrate the tell-tale skull characteristics of each, as described to me by Darryl over lunch on his last day in camp.
Australopithecus africanus is the oldest hominid found in South Africa. The pillars that run from nose to canines is a particular hallmark. While there are more complete skulls, Darryl de Ruiter’s favorite is Sts-52, from the site of Sterkfontein, because of its complete upper and lower dentition. (Illustration by Andrew Howley)
In earlier posts, I referred to this species as “Paranthropus robustus.” Darryl prefers “Australopithecus robusuts,” because in his view the relationships between the two groups is still unclear. His favorite specimen is the cranial base Sk-18 from Swartkrans, because he prepared it and “it sat on my desk for two years.” (Illustration by Andrew Howley)
Also found in this region of South Africa by Lee Berger, Australopithecus sediba is one of the most recent additions to the ever-bushier human family tree, and made its debut with two remarkably complete skeletons. The skull is flatter and more square like ours, but the body has more primitive features in its shoulders and feet in particular. So far this skull, MH-1, is the only to be excavated, though the site of Malapa promises to hold more. (Illustration by Andrew Howley)
Most recent, and most clearly related directly to modern humans among the hominids found in South Africa is Homo erectus. The prominent brow ridge known as a supraorbital torus is the main giveaway for an erectus skull, though the big brain case is also not likely to be confused with those of the earlier species. Swarkrans’ SK-847 is the one Darryl favors, because it could be the oldest one there is. Others debate whether it is erectus or another species. Darryl sticks to his guns. Or rather, his stone hand axes. (Illustration by Andrew Howley)
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