'Out Of Africa' Theory
Boost: Skull Dating Suggests Modern Humans Evolved In Africa
ScienceDaily
(Jan. 12, 2007) — Reliably dated
fossils are critical to understanding the course of human evolution. A human
skull discovered over fifty years ago near the town of Hofmeyr, in the
Eastern Cape Province of South Africa, is one such fossil. A study by an
international team of scientists led by Frederick Grine of the Departments of
Anthropology and Anatomical Sciences at Stony Brook University in New York
published in Science magazine has dated the skull to 36,000 years ago. This
skull provides critical corroboration of genetic evidence indicating that
modern humans originated in sub-Saharan Africa and migrated about this time
to colonize the Old World. (Science January
12, 2007) "The Hofmeyr skull gives us the first insights
into the morphology of such a sub-Saharan African population, which means the
most recent common ancestor of all of us - wherever we come from," said
Grine.
The
Hofmeyr Skull. Scientists have now dated the skull as being 36,000 years old.
The great similarity of this skull to skulls of the same age from Eurasian
finds confirms the "Out of Africa"-hypothesis. Modern humans broke
out of their place of origin around 40,000 years ago - from Africa south of
the Sahara - and populated the world. (Image: Frederick
E. Grine) Although the skull was found over half a century
ago, its significance became apparent only recently. A new approach to dating
developed by Grine team member Richard Bailey and his colleagues at Oxford
University allowed them to determined its age at just over 36,000 years ago
by measuring the amount of radiation that had been absorbed by sand grains
that filled the inside of the skull’s braincase. At this age, the skull fills
a significant void in the human fossil record of sub-Saharan Africa from the
period between about 70,000 and 15,000 years ago. During this critical period,
the archaeological tradition known as the Later Stone Age, with its
sophisticated stone and bone tools and artwork appears in sub-Saharan Africa,
and anatomically modern people appear for the first time in Europe and
western Asia with the equally complex Upper Paleolithic archeological
tradition. In order to establish the affinities of the Hofmeyr
fossil, team member Katerina Harvati of the Max Planck Institute for
Evolutionary Anthropology in Leipzig, Germany, used 3-dimensional
measurements of the skull known to differentiate recent human populations
according to their geographic distributions and genetic relationships. She
compared the Hofmeyr skull with contemporaneous Upper Paleolithic skulls from
Europe and with the skulls of living humans from Eurasia and sub-Saharan
Africa, including the Khoe-San (Bushmen). Because the Khoe-San are
represented in the recent archeological record of South Africa, they were
expected to have close resemblances to the South African fossil. Instead, the
Hofmeyr skull is quite distinct from recent sub-Saharan Africans, including
the Khoe-San, and has a very close affinity with the European Upper
Paleolithic specimens. The field of paleoanthropology is known for its
hotly contested debates, and one that has raged for years concerns the
evolutionary origin of modern people. A number of genetic studies (especially
those on the mitochondrial DNA) of living people indicate that modern humans
evolved in sub-Saharan Africa and then left between 65,000 and 25,000 years
ago to colonize the Old World. However, other genetic studies (generally on
nuclear DNA) argue against this African origin and exodus model. Instead,
they suggest that archaic non-African groups, such as the Neandertals, made
significant contributions to the genomes of modern humans in Eurasia. Until
now, the lack of human fossils of appropriate antiquity from sub-Saharan
Africa has meant that these competing genetic models of human evolution could
not be tested by paleontological evidence. The skull from Hofmeyr has changed that. The
surprising similarity between a fossil skull from the southernmost tip of
Africa and similarly ancient skulls from Europe is in agreement with the
genetics-based "Out of Africa" theory, which predicts that humans
like those that inhabited Eurasia in the Upper Paleolithic should be found in
sub-Saharan Africa around 36,000 years ago. The skull from South Africa
provides the first fossil evidence in support of this prediction. Reference: F.E. Grine, R.M. Bailey, K.
Harvati, R.P. Nathan, A.G. Morris, G.M. Henderson, I. Ribot, A.W.G. Pike. Late
Pleistocene Human Skull from Hofmeyr, South Africa and Modern Human Origins. Science,
12. January 2007 Adapted from materials provided by Max Planck Society. |
