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Archiver > GENEALOGY-DNA > 2007-03 > 1172767486


From: ellen Levy <>
Subject: Re: [DNA] Lactose tolerance evolved recently
Date: Thu, 1 Mar 2007 08:44:46 -0800 (PST)
In-Reply-To: <BAY111-DAV9B8B8701C28FACAAD8843B1800@phx.gbl>


Lawrence & List:

I'm not sure what Alan R. meant by suggesting
tolerance to some degree existed in Europe "since the
beginning." I'm not sure Alan is still posting to the
list or wishes to comment. Obviously, I'm not clear
what evidence Alan was relying on for the suggestion
of tolerance "since the beginning" (I suspect the
language "beginning" merely indicates "pre-Neolithic
in origin). It may have just been speculation on his
part.

I think the archaeological record can address this
question to a certain extent. Unfortunately, I
haven't closely followed those archaeologists studying
and writing about domestication of dairying animals.
I would be very surprised if domestication of such
animals occurred first in northeastern Europe and not
in the Middle East. I assume the earliest dairying
cultures relied on sheep and goats, not cattle.

Regarding dairying in Europe, Joao Zilhao, an
archaeologist I written about before to the list, has
found evidence of domesticated sheep during the
earliest Neolithization of Portugal around 6900 BC.

However, the question of whether domestication is tied
to the Neolithic cultural package as a whole is
questioned by Didier Binder of the University of
Provence, who has studied the Mesolithic/Neolithic
transition in France and northern Italy. According to
Binder, there may be evidence of the presence of sheep
in the Late Mesolithic assemblages at Azzura cave,
Chateauneuf and Dourgne. These assemblages, however,
are very controversial and it appears Binder's view is
not widely supported. For example, at Azzure Cave,
the presence of sheep is believed to be an intrusive
element from the overlying ceramic layers. And at
Chateauneuf, the excavations in 1979 did not produce
evidence of Mesolithic sheep. However, Binder
complains that a precise faunal investigation of each
layer was never properly performed during earlier
excavations of the site, which would have more closely
addressed the issue of Neolithic intrusion.

According to Peter Bogucki of Princeton University,
the keeping of livestock in north-central Europe was
not the product of the local adoption of this
technology by indigenous foraging peoples. He states
a number of supportive factors for the demic diffusion
theory in general in this region, from no in situ
development of pottery in this region to distinctive
housing and settlement forms by Neolthic settlers. He
also notes that the two major livestock species -
sheep and goat - have no native, wild, conspecific
forms in Central Europe and were introduced from
southeast Europe and ultimately from southwest Asia.

I wanted to make one more comment concerning spread of
a lactose tolerant gene among the populations of
Europe. I am certainly not discounting the
possibility that such tolerance could have been tied
with specific haplogroups as part of the demic
diffusion process. The evidence suggests that
sedentary farming communities reproduced more quickly
and in greater numbers than hunter-gatherer
communities. As a result of their ever-expanding
population, it is easy to envision how a beneficial
dietary genetic mutation among these early
agriculturalists could have spread fairly quickly
among the European population.

However, one thing to consider is that if lactose
tolerance first developed in the Middle East, where
sheep and goats were first domesticated, would not the
expanding Neolithic agriculturalists into Europe
already have carried this beneficial gene? Another
interesting point to consider is that while the
Neolithic agricultural package first arrived in
southeastern and southern Europe, why did such
tolerance remain relatively limited in comparison to
northern and northeastern Europe, where such tolerance
became much more expansive? I assume that other
selective pressures may have eventually had an impact
on the spread of this gene, particularly ones based on
dietary subsistence. For example, if certain
populations in northern Europe became more
significantly reliant on domesticated sheep and cattle
for subsistence, then additional selective pressure
would have favored the spread of this gene than would
have been present among southern European and Middle
Eastern groups, which may have relied more on plant
resources.

Ellen Coffman






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