Old human fossils break new ground

 

The oldest know fossils of modern humans have been unearthed in Ethiopia. They tell strange tales of ritual burials and butchered hippos, writes Dick Ahlstrom.An Irish engineer designed a diving bell so that men could workunderwater, excavating and levelling a site. His work transformed Dublin's docklands, writes Mary Mulvihill

aPalaeontologists in Ethiopia have found the oldest known fossils of near-modern humans, pushing back the appearance of our earliest modern ancestors to about 160,000 years ago. The scientists also discovered intriguing clues about how our ancestors lived and what they ate.

The research teams found the skulls of two adults and a child, plus skull pieces and isolated teeth from seven other individuals. All were of the same species and were found in a geological layer that included ancient river and beach deposits.

Details of the remarkable finds are detailed today in the journal, Nature. The scientists were working in Ethiopia's Middle Awash area of Afar Regional State near Herto village. It took three years to clean and restore the fossils before they could be compared and analysed.

Also recovered were stone artefacts including tools plus modified animal bones that showed signs of tool marks. The human skulls also showed signs of cut marks made by tools, leading the researchers to suggest that this demonstrated a form of early mortuary practice. Not in doubt was what these early humans had when dinner rolled around. The Herto study area was first identified when palaeontologists discovered a butchered fossil hippopotamus skull and associated stone artefacts.

One adult cranium was found in situ, still embedded in the sediments, but the child's skull was found in 200 pieces scattered over a wide area. The scientists assumed that it had eroded from the sediments to be then broken up and scattered by grazing animals, wind and rain wash. Dr Berhane Asfaw in Ethiopia first cleaned the pieces and then undertook the painstaking reconstruction of this skull. He was able to use tiny anatomical clues in the process, such as impressions of individual blood vessels that allowed him to align each skull fragment.

"It was an anatomical puzzle in three dimensions," he says. "I was able to use modern human skulls as the key to put the child's cranium back together again." There were no clues as to the relationship between any of these individuals. And while there was no evidence of intentional burial of the crania, no other bones of the skeletons have yet been found.

Contemporaries of these hominids handled these skulls for some time, however. One of the adult skulls showed parallel incisions around the perimeter of the skull, superficial cut marks made by a stone tool.

The markings on the child's cranium were even more intriguing. The skull base showed signs of cut marks made by a very sharp stone flake. The rear of the cranium was broken away and these broken edges were then polished. All of these skull markings were in place before the skulls found their way into the sediments that eventually fossilised them. This discovery lends yet more credence to the belief that modern humans first arose in Africa according to Dr Tim White of the University of Berkeley. "Now we have a great sequence of fossils showing that we evolved in Africa, and not all over the globe," he says.

The report on duck fossils will now run in Science Today on Thursday June 26th