LACTOSE INTOLERANCE IN ANCIENT EUROPEAN FARMERS
By analysing DNA
extracted from the petrous bones of skulls of ancient Europeans, scientists
have identified that these peoples remained intolerant to lactose (natural
sugar in the milk of mammals) for 5,000 years after they adopted agricultural
practices and 4,000 years after the onset of cheese-making among Central European
Neolithic farmers.
The findings published
online in the scientific journalNature Communications (21 Oct) also
suggest that major technological transitions in Central Europe between the
Neolithic, Bronze Age and Iron Age were also associated with major changes in
the genetics of these populations.
For the study, the
international team of scientists examined nuclear ancient DNA extracted from
thirteen individuals from burials from archaeological sites located in the
Great Hungarian Plain, an area known to have been at the crossroads of major
cultural transformations that shaped European prehistory. The skeletons sampled
date from 5,700 BC (Early Neolithic) to 800 BC (Iron Age).
It took several years
of experimentation with different bones of varying density and DNA preservation
for the scientists to discover that the inner ear region of the petrous bone in
the skull, which is the hardest bone and well protected from damage, is ideal
for ancient DNA analysis in humans and any other mammals.
According to Professor
Ron Pinhasi from the UCD Earth Institute and UCD School of Archaeology,
University College Dublin, the joint senior author on the paper, "the high
percentage DNA yield from the petrous bones exceeded those from other bones by
up to 183-fold. This gave us anywhere between 12% and almost 90% human DNA in
our samples compared to somewhere between 0% and 20% obtained from teeth,
fingers and rib bones."
For the first time,
these exceptionally high percentage DNA yields from ancient remains made it
possible for scientists to systematically analyse a series of skeletons from
the same region and check for known genetic markers including lactose
intolerance.
"Our findings
show progression towards lighter skin pigmentation as hunter and gatherers and
non-local farmers intermarried, but surprisingly no presence of increased
lactose persistence or tolerance to lactose" adds Professor Pinhasi.
"This means that
these ancient Europeans would have had domesticated animals like cows, goats
and sheep, but they would not yet have genetically developed a tolerance for
drinking large quantities of milk from mammals," he says.
According to Professor
Dan Bradley from the Smurfit Institute of Genetics, Trinity College Dublin,
co-senior author on the paper, "our results also imply that the great
changes in prehistoric technology including the adoption of farming, followed
by the first use of the hard metals, bronze and then iron, were each associated
with the substantial influx of new people. We can no longer believe these
fundamental innovations were simply absorbed by existing populations in a sort
of cultural osmosis."
Comments
Post a Comment