http://www.sciencedaily.com/releases/2007/07/070718140829.htm
Science Daily — New research published in the journal Nature (19 July)
has proved the single origin of humans theory by combining studies of
global genetic variations in humans with skull measurements across the
world. The research, at the University of Cambridge and funded by the
Biotechnology and Biological Sciences Research Council (BBSRC),
represents a final blow for supporters of a multiple origins of humans
theory.
Competing theories on the origins of anatomically modern humans claim
that either humans originated from a single point in Africa and
migrated across the world, or different populations independently
evolved from homo erectus to home sapiens in different areas.
The Cambridge researchers studied genetic diversity of human
populations around the world and measurements of over 6,000 skulls
from across the globe in academic collections. Their research knocks
down one of the last arguments in favour of multiple origins. The new
findings show that a loss in genetic diversity the further a
population is from Africa is mirrored by a loss in variation in
physical attributes.
Lead researcher, Dr Andrea Manica from the University's Department of
Zoology, explained: "The origin of anatomically modern humans has been
the focus of much heated debate. Our genetic research shows the
further modern humans have migrated from Africa the more genetic
diversity has been lost within a population.
"However, some have used skull data to argue that modern humans
originated in multiple spots around the world. We have combined our
genetic data with new measurements of a large sample of skulls to show
definitively that modern humans originated from a single area in
Sub-saharan Africa."
The research team found that genetic diversity decreased in
populations the further away from Africa they were - a result of
'bottlenecks' or events that temporarily reduced populations during
human migration. They then studied an exceptionally large sample of
human skulls. Taking a set of measurements across all the skulls the
team showed that not only was variation highest amongst the sample
from south eastern Africa but that it did decrease at the same rate as
the genetic data the further the skull was away from Africa.
To ensure the validity of their single origin evidence the researchers
attempted to use their data to find non-African origins for modern
humans. Research Dr Francois Balloux explains: "To test the
alternative theory for the origin of modern humans we tried to find an
additional, non-African origin. We found this just did not work. Our
findings show that humans originated in a single area in Sub-Saharan
Africa."
Note: This story has been adapted from a news release issued by
Biotechnology and Biological Sciences Research Council.
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