-- Robert Preidt
THURSDAY, Aug. 25 (HealthDay News) -- Interbreeding between
modern humans, Neanderthals and another close relative may have
passed on genes that boost peoples' immune systems today,
Modern humans, Neanderthals and a recently discovered relative
called Denisovans share a common African ancestor, the team of
scientists explained in the Aug. 25 online issue of
Science. However, the groups diverged into separate, distinct populations about 400,000 years ago, noted the Stanford University School of Medicine researchers.
Neanderthals moved into Europe and West Asia, Denisovans
migrated into East Asia, and modern humans remained in Africa until
about 65,000 years ago. But as modern humans expanded their range
out of Africa they came into contact with the two other groups and
interbreeding is thought to have occurred.
The last Neanderthals died about 30,000 years ago, but research
has shown that some modern humans have as much as 4 percent
Neanderthal DNA. People living today also have up to 6 percent of
their DNA from Denisovans, a species which has only recently been
The authors of this new study have found that this crossbreeding
gave modern humans new variants of immune system genes called HLA
class I genes. This DNA plays a crucial role in people's ability to
identify and kill pathogens.
"The cross breeding wasn't just a random event that happened, it gave something useful to the gene pool of the modern human," senior author Peter Parham, a professor of structural biology and of microbiology and immunology, said in a Stanford news release.
The amount of people's HLA class I genes attributed to
now-extinct Neanderthals or Denisovans varies widely depending on
geography, his team added. For example, people from Papua New
Guinea owe up to 95 percent of their gene variants from one class
of HLA to this intermixing with the two other species, compared to
80 percent for Asians and 50 percent for Europeans.
The Smithsonian Institution has more about
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