THE DISCOVERY OF THE SKULL OF HUMANKIND’S OLDEST ANCESTOR

By Charlotte Fox

Recently, a 3.8-million-year old fossil was discovered by a farmer in eastern Ethiopia, and it is believed to be the skull of humankind’s oldest known ancestor. The fossil belongs to an ancient Australopithecus Anamnesis, the direct ancestor of the “Lucy” species (Australopithecus Afarensis). It dates back to a time when our ancestors were coming out of the trees to walk on two legs, but still had defined ape-like jutting faces, powerful jaws and small brains. Previously, only ‘a handful of teeth, some limb bones and a few fragments of skull’ had been discovered to provide clues about the appearance and lifestyle of the Lucy species, but now there is a complete adult male skull, named MRD.

The skull shows that MRD had a small brain (a quarter the size of a modern human’s brain), and was already losing some of its ape-like features. Its teeth are smaller than the teeth seen in earlier fossils and the powerful jaw and prominent cheekbones seen in Lucy (which scientists think helped them chew tough food during dry seasons when less vegetation was available) had already started to develop. The dating of the skull also shows that the Lucy species coexisted for a period of at least 100,000 years, which challenges the idea of linear evolution, in which one species disappears and is replaced by a new one. Anamnesis, which stretches from 4.2 - 3.8 million years ago is still thought to be Lucy’s ancestor, but continued to exist after the Lucy group diverged from them. Geological evidence shows that the landscape featured extremely steep hills, volcanoes, lava flows and rifts that could have isolated populations, causing them to diverge. Fossil pollen grains and chemical remains of fossil plants and algae on the skull show that the individual lived by a river or lake surrounded by vegetation.

Professor Fred Spoon of the Natural History Museum described Anamnesis as the, “Oldest-known species that is unambiguously part of the human evolutionary tree.” Older fossils, such as Ardi, which is 4.4 million years old, are more controversial (some believe it is an ancestor of humans while others believe it is an extinct form of ape), and therefore is not considered the oldest known ancestor of humankind.

Spoon also said that, “This cranium looks set to become another celebrated icon of human evolution,” and that it will, “Substantially affect thinking on the evolutionary family tree of early hominins.”

Archaeologists are investigating the area in which the skull was found to see if there are any other extremely old fossils buried there, which will help to further explain and uncover the rules of evolution.