Oldest-Ever Skulls Back ‘Out of Africa’ Theory
Berkeley researchers have discovered the oldest-known skulls of modern humans, 160,000-year-old Ethiopian fossils from the dawn of humanity that strongly support the theory that modern humans evolved in Africa.
The three skulls -- two from an adult and one from a child -- suggest that people very much like us were thriving on the shores of a now-vanished freshwater lake in Ethiopia, butchering hippopotamuses and scaling fish, at a time when Europe was suffering a severe ice age. Eventually, as their numbers grew, they left this idyllic region to populate the rest of the world.
Genetic studies have long suggested an African origin for the human species, but the fossil evidence supporting such an idea has been sparse -- fossils have been fragmentary and their dating has often been ambiguous.
Intact Skulls
The new skulls are intact, however, and the dating is firm, placing them at least 30,000 years earlier than the best previously known skulls, and perhaps as much as 60,000 years earlier.
“Now, the fossil evidence meshes with the molecular evidence,” said paleoanthropologist Tim White of UC Berkeley, lead author of the two papers published today in the journal Nature. “With these new crania, we can now see what our direct ancestors looked like.”
The new skulls “are probably some of the most significant discoveries of early Homo sapiens so far, owing to their completeness and well-established antiquity,” said Chris Stringer of London’s Natural History Museum, one of the leading proponents of the “Out of Africa” theory of human evolution. “These are wonderful finds.”
A series of fossils from Ethiopia now shows the complete evolution of humans from nearly 2 million years ago until the present.
“Now, we have a great sequence of fossils showing that we evolved in Africa and not all over the globe,” White said.
The new fossils also provide strong evidence that the Neanderthals of Europe -- who appeared about 230,000 years ago and disappeared 200,000 years later -- were an evolutionary dead end that did not contribute to our genetic heritage.
The fossils “show that near-humans had evolved in Africa long before the European Neanderthals disappeared,” said Berkeley biologist F. Clark Howell. “They thereby demonstrate conclusively that there was never a Neanderthal stage in human evolution.”
White and his colleagues have been working for more than two decades in the fossil-rich Middle Awash area of Ethiopia, in the Afar Depression. The new finds were located at Herto village on the Bouri peninsula, about 140 miles northeast of Addis Ababa.
White himself discovered the area on Nov. 16, 1977, when he observed the fossilized skull of a hippopotamus that had been butchered and stone artifacts protruding from the surface. When the team returned 11 days later, members found the hominid, or human-like, fossils.
Ultimately, Berkeley graduate student David DeGusta found the intact skull of a 20- to 30-year-old embedded in ancient cemented sands.
‘A Taste for Hippos’
Turkish paleontologist Cesur Pehlevan subsequently found a less intact adult skull nearby, and Berhane Asfaw of the Rift Valley Research Service in Addis Ababa found a child’s shattered cranium.
The team also found skull pieces and teeth from seven other hominids, large numbers of hippopotamus and fish bones and more than 640 stone artifacts, including hand axes, flake tools and rare blades. The bones “clearly show that the Herto people had a taste for hippos, but we can’t tell whether they were killing them or scavenging them,” said anthropologist Yonas Beyene of Ethiopia’s Authority for Research and Conservation of the Cultural Heritages.
It took the researchers three years -- working around their teaching and administrative duties -- to clean up the fossils for further study. Asfaw painstakingly assembled the more than 200 pieces of the child’s cranium to complete the skull, which, like the others, is lacking a jaw bone.
All the skulls remain at the National Museum of Ethiopia, where the work was performed.
Meanwhile, teams at the Berkeley Geochronological Center and the Los Alamos National Laboratory in New Mexico dated soil samples taken from above and below the fossils, yielding a very precise date for them.
All three skulls were clearly Homo sapiens, although with slight differences that mark them as more primitive, White says. Key findings were that the skulls did not have the prominent brow ridges characteristic of older species; they also had a higher cranial vault. The team decided to give them the sub-species name Homo sapiens idaltu, from the Afar word for “elder.”
The male skull is long and rugged, with heavily worn upper teeth. The skull itself is slightly larger than the largest modern human skulls, and the cranial capacity -- the space for the brain -- slightly larger. An anthropological reconstruction of the face looks very much like that of a modern human.
The skulls also provide insight into early mortuary practices, including the de-fleshing of skulls. The second adult skull had superficial cut marks made by a tool that had been drawn repeatedly across the skull’s surface. The marks are distinct from those usually produced in the de-fleshing of a skull.
Cuts on Skull
In the child’s skull, cut marks made by a very sharp stone flake were found deep in nooks and crannies of the skull’s base. The rear part of the cranial base was broken away and the edges polished. The sides of the skull show a deep polish that may have formed from repeated handling after it was de-fleshed.
This evidence, along with the lack of other body parts, suggests that the skulls were processed separately from the rest of the body. Similar modifications have been observed in societies, including some in New Guinea, in which the skulls of ancestors are preserved and worshiped.
Despite the accumulating evidence for the “Out of Africa” theory, there are still holdouts, notably University of Michigan anthropologist Milford Wolpoff. This group argues that modern humans evolved independently at several different locations around the world, including Europe, China and Indonesia. This group’s interpretation is based on controversial fossil skulls that are fragmentary, however, and the dates are less conclusive.
“There will always be skeptics,” White said, but “the evidence that modern humans basically came form Africa is now very large.”
