But all humans can run Re: Long distance running in some human populations recent

Marc Verhaegen wrote:

Born to Run Long Distance
By Michael Balter
ScienceNOW Daily News
10 September 2007
Marathon running might be in some people's genes, according to a new study,
which shows that a genetic mutation that boosts muscle endurance has spread
widely in some human populations.
http://sciencenow.sciencemag.org/cgi/content/full/2007/910/3?etoc

There are two types of skeletal muscle fibers. Fast fibers, which use sugars
for fuel and do not require oxygen, kick in for tasks that require maximum
force and quick action, such as sprinting. Slow fibers, which employ
oxygen-using (or aerobic) pathways, power activities that require endurance,
such as long-distance running. A protein called alpha-actinin-3 is made
mostly by fast fibers and is implicated in their capacity for rapid force
generation. About 18% of people of European descent do not produce the
protein at all due to mutations in both their copies of the gene ACTN3,
which codes for alpha-actinin-3. Previous studies have shown that endurance
athletes such as long-distance runners have higher frequencies of this
mutation, whereas sprinters and athletes in other sports that require quick
muscle strength have lower frequencies.

Researchers led by geneticist Kathryn North of the Institute for
Neuromuscular Research in Sydney, Australia, decided to investigate how
ACTN3 affects muscle activity so dramatically. The team first created mice
that lacked a functioning gene. The researchers found that the mice's fast
fibers contained much higher levels of several enzymes associated with
aerobic metabolism, suggesting that the absence of alpha-actinin-3 caused
the fast fibers to work more like slow fibers. Moreover, on a treadmill, the
altered mice could run about 33% farther before becoming exhausted than
could control rodents, indicating that the ACTN3 mutation enhances
endurance.

To trace the gene's evolutionary history in humans, the team sequenced a
segment of DNA that includes ACTN3 in 96 people from Europe, Asia, or
Africa. Earlier work had found that the frequency of the mutant gene varies
in human populations, ranging from an average of 10% in Africans to about
50% in Europeans and Asians. North and her co-workers found that the region
surrounding the mutant version of the gene showed less variability than did
other parts of the genome, a sign of positive natural selection. The authors
suggest that the mutation might have had an adaptive advantage for modern
humans, who migrated out of Africa into Europe and Asia beginning about
60,000 years ago. The research appeared online 9 September in Nature
Genetics.

Michael Nachmann, a geneticist at the University of Arizona, Tucson, says
that the team's experiments are "a great test" of ACTN3's role and support
the conclusion that the mutation "affects some kind of athletic ability."
Marcio Pie, an evolutionary biologist at the Federal University of Paraná in
Curitiba, Brazil, calls the study a "beautiful piece of work." Although
North and her colleagues declined to speculate on why the frequency of the
mutation differs among human groups and what its adaptive role might have
been, Pie says that this question "would be interesting to explore further."
.

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