14 DAY TRIAL // Even if we may have separated totally from chimps 4 million years ago, new findings from Georgia reveal that 1.77-million years ago we were just little more than apes. The fossils of three adults and a teenager were dug near the Dmanisi town (Caucasus area) by a team led by David Lordkipanidze of the Georgian National Museum and show a higher variety in early humans than once believed.
The bones come with a surprising mixture of primitive and evolved traits, that does not match neatly into a continuous evolutionary lineage. The well-preserved fossils resemble Homo erectus, a Homo species that first emerged in Africa about 2 million years ago, being the first human species which spread out of Africa into Europe and Asia.
In fact, these are the oldest man fossils encountered outside Africa. The spines and lower limbs, with well developed arches, are very similar to ours, thus they were adapted for long distance travel and the relatively small size difference between males and females places this species closer to H. sapiens.
But unlike other H. erectus, these ones have some traits in common with the earlier Homo habilis (skilful man) and even with the more archaic genus of Australopithecus, which emerged in Africa about 4 million years ago: their brain-to-body mass ratio is extremely low, and their body size just slightly larger than that of a chimp. The biggest males in the group did not overcome 48-to-50 kg (96-110 pounds) in weight, and 1.47 to 1.61 m (56.4-64.4 inches) in height. Another surprising trait was their inability to rotate the forearm forward.
The teenager's skeleton was of especially great interest, as "post-cranial" (everything except the skull) skeleton is harder to fossilize.
Adding to the recent discoveries of Lake Turkana (Kenya), the Dmanisi findings point that the Homo genus spreading across Africa and Eurasia "was less modern and more variable than sometimes supposed," said Harvard's Daniel Leiberman. If the Georgian fossils are H. erectus, then "early H. erectus was not only quite widespread but also unusually variable in both body and brain size.", added Leiberman.
The odd mix of primitive and complex traits in the Dmanisi hominins may also mean they had adapted to the local environments, suggest the discoverers. Now it is less likely that H. erectus evolved from H. habilis, as the two co-existed, but rather had common ancestors.
The recent discovery of two African fossils, a H. erectus skull 1.55 million years old and a H. habilis jaw 1.44 million years old, increased greatly the co-habitance interval. "Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis. The fact that they stayed separate as individual species for a long time suggests that they had their own ecological niche, thus avoiding direct competition," said Meave Leakey, one of the discoverers of the African fossils.