[lit-ideas] Sapient Hominids. . . Just forget about it?
- From: Eric Yost <mr.eric.yost@xxxxxxxxx>
- To: lit-ideas@xxxxxxxxxxxxx
- Date: Thu, 08 Sep 2005 23:52:40 -0400
http://news.yahoo.com/news?tmpl=story&u=/ap/20050909/ap_on_sc/brain_evolution
Genes Show Signs Brain Still Evolving
By LAURAN NEERGAARD, AP Medical Writer 1 hour, 14 minutes ago
WASHINGTON - The human brain may still be evolving. So suggests new
research that tracked changes in two genes thought to help regulate
brain growth, changes that appeared well after the rise of modern
humans 200,000 years ago.
That the defining feature of humans — our large brains — continued
to evolve as recently as 5,800 years ago, and may be doing so today,
promises to surprise the average person, if not biologists.
"We, including scientists, have considered ourselves as sort of the
pinnacle of evolution," noted lead researcher Bruce Lahn, a
University of Chicago geneticist whose studies appear in Friday's
edition of the journal Science.
"There's a sense we as humans have kind of peaked," agreed Greg
Wray, director of Duke University's Center for Evolutionary
Genomics. "A different way to look at is it's almost impossible for
evolution not to happen."
Still, the findings also are controversial, because it's far from
clear what effect the genetic changes had or if they arose when
Lahn's "molecular clock" suggests — at roughly the same time period
as some cultural achievements, including written language and the
development of cities.
Lahn and colleagues examined two genes, named microcephalin and
ASPM, that are connected to brain size. If those genes don't work,
babies are born with severely small brains, called microcephaly.
Using DNA samples from ethnically diverse populations, they
identified a collection of variations in each gene that occurred
with unusually high frequency. In fact, the variations were so
common they couldn't be accidental mutations but instead were
probably due to natural selection, where genetic changes that are
favorable to a species quickly gain a foothold and begin to spread,
the researchers report.
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