Tom Bri:
...
>
> I am guessing that neolithic peoples mostly made the transition with
> little
> difficulty. Not saying it was 100% good for them. Just that it didn't
> make
> them sick to their stomachs.
>
> I have met people who just simply can not drink milk. They really get
> seriously sick on it. But that is a pretty uncommon thing.
Except that that doesn't jibe with what I found in these articles that claim
that cattle were first domesticated about 9,000 years ago but people didn't
start drinking their milk until "later" and lactose tolerance didn't develop
until about 7,000 years ago. It doesn't make sense that Paleolithic hunter
gatherers were drinking milk, then stopped drinking it after they
domesticated cattle.
Also, wouldn't lactose intolerance effects have had to be fairly significant
for enough people to give the lactose tolerant genes the "enormous selective
advantage" that scientists found they provide? The theory stated in one of
the articles is that lactose tolerant people "not only gained extra energy
from lactose but also, in drought conditions, would have benefited from the
water in milk" because people "who were lactose intolerant could have risked
losing water from diarrhea."
--------------
The Evolution of Lactose-Tolerance
Category: Culture
Posted on: December 11, 2006 12:31 PM, by Jonah Lehrer
http://scienceblogs.com/cortex/2006/12/the_evolution_of_lactosetolera.php
Throughout most of human history, the ability to digest lactose, the
principal sugar of milk, has been switched off after weaning because the
lactase enzyme that breaks the sugar apart is no longer needed. But when
cattle were first domesticated 9,000 years ago and people later started to
consume their milk as well as their meat, natural selection would have
favored anyone with a mutation that kept the lactase gene switched on.
Lactose tolerance is part of evolution, say scientists
http://www.whatistheword.com/story/SciTech_1065.html
BONN: Humans became tolerant towards lactose only about 7,000 years ago and
milk was not part of the diet for them in ancient times, according to new
research by scientists at the Mainz University in Germany.
Lactose tolerance in East Africa points to a surprisingly recent moment in
human evolution
11.12.2006 - The ability to digest milk in adulthood was conferred by
genetic changes that occurred as recently as 3,000 years ago, a team of
geneticists has found.
http://medicalweeknews.com/news/Lactose-tolerance-in-East-Africa-points-to-a
-surprisingly-recent-moment-in-human-evolution/
...
The principal mutation, found among Nilo-Saharan-speaking ethnic groups of
Kenya and Tanzania, arose 2,700 to 6,800 years ago, according to genetic
estimates, Tishkoff's group reported Monday in the journal Nature Genetics.
This fits well with archaeological evidence suggesting that pastoral peoples
from the north reached northern Kenya about 4,500 years ago and southern
Kenya and Tanzania 3,300 years ago.
Two other mutations were found, among the Beja people of northeastern Sudan
and tribes of the same language family, Afro-Asiatic, in northern Kenya.
Genetic evidence shows that the mutations conferred an enormous selective
advantage on their owners, enabling them to leave almost 10 times as many
descendants as people without such mutations did. The mutations have created
"one of the strongest genetic signatures of natural selection yet reported
in humans," the researchers write.
The survival advantage was so powerful perhaps because those with the
mutations not only gained extra energy from lactose but also, in drought
conditions, would have benefited from the water in milk. People who were
lactose intolerant could have risked losing water from diarrhea, Tishkoff
said.
Diane Gifford-Gonzalez, an archaeologist at the University of California,
Santa Cruz, said the findings were "very exciting" because they "showed the
speed with which a genetic mutation can be favored under conditions of
strong natural selection, demonstrating the possible rate of evolutionary
change in humans."
The genetic data fitted in well, she said, with archaeological and
linguistic evidence about the spread of pastoralism in Africa. The first
clear evidence of cattle in Africa is from a site 8,000 years old in
northwestern Sudan. Cattle there were domesticated independently from two
other domestications, in the Near East and the Indus Valley of India.
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