Expatica news

Oldest hominid discovered is 7 million years old

   CHICAGO, February 27, 2008 – French fossil hunters have pinned down the
age of Toumai, which they contend is the remains of the earliest human ever
found, at between 6.8 and 7.2 million years old.
   The fossil was discovered in the Chadian desert in 2001 and an intense
debate ensued over whether the nearly complete cranium, pieces of jawbone and
teeth belonged to one of our earliest ancestors.
   Critics said that Toumai’s cranium was too squashed to be that of a hominid
— it did not have the brain capacity that gives humans primacy — and its
small size indicated a creature of no more than 120 centimetres (four feet) in
height, about the size of a walking chimp.
   In short, they said, Toumai had no right to be baptised with French
researcher Michel Brunet’s hominid honorific of Sahelanthropus tchadensis —
he was simply a vulgar ape.
   Toumai’s supporters used 3D computer reconstructions to show that the
structure of the cranium had clear differences from those of gorillas and
chimps and indicates that Toumai was able to walk upright on two feet,
something our primate cousins cannot do with ease.
   If Toumai is truly an early human, that means that the evolutionary split
between apes and humans occurred far earlier than previously thought.
   And pinning down his age is key to redrawing the evolutionary map.
   "The radiochronological data concerning Sahelanthropus tchadensis … is an
important cornerstone both for establishing the earliest stages of hominid
evolution and for new calibrations of the molecular clock," Brunet wrote in a
study which will appear in the March 4 edition of the Proceedings of the
National Academy of Sciences.
   "Thus, Sahelanthropus tchadensis testifies that the last divergence between
chimps and humans is certainly not much more recent than 8 Ma (million years
   Toumai also probably lived "very close in time to this divergence contrary
to the unlikely ‘provocative explanation,’ which recently suggested a
‘possible hybridization in the human-chimp lineage before finally separating
less than 6.3 (million years ago)," the authors concluded.
   If Toumai — the name means "hope of life" in the local Goran language —
is accepted as a human, the implications are profound.
   The fossil was found some 2,500 kilometers (1,500 miles) west of the Great
Rift Valley. If that is still seen as humankind’s ancestral home, it implies
the early hominids ranged far wider from East Africa, and far earlier, than
previously thought.
   The discovery also implies hominids evolved quickly from apes after they
split from a common primate ancestry.
   Hominids are considered the forerunners of anatomically modern humans, who
appeared on the scene about 200,000 years ago.
   Still unclear, though, is the exact line of genealogy from these small,
rather ape-like creatures to the rise of the powerfully-brained Homo sapiens.