Humans ditched DNA to evolve smooth penises and bigger brains
Sex would be a very different proposition for humans if -- like some
animals including chimpanzees, macaques and mice -- men had penises studded
with
small, hard spines.
Now researchers at Stanford University in California have found a
molecular mechanism for how the human penis could have evolved to be so
distinctly
spine-free. They have pinpointed it as the loss of a particular chunk of
non-coding DNA that influences the expression of the androgen receptor gene
involved in hormone signaling.
"It is a small but fascinating part of a bigger picture about the
evolution of human-specific traits," said Gill Bejerano, a developmental
biologist
at Stanford who led the work along with colleague David Kingsley. "We add a
molecular perspective to a discussion that has been going on for several
decades at least."
Published in Nature today, the research also suggests a molecular
mechanism for how we evolved bigger brains than chimpanzees and lost the small
sensory whiskers that the apes -- who are amongst our closest relatives and
with whom it has been estimated we share 96% of our DNA -- have on their face.
Monogamous strategy
It has long been believed that humans evolved smooth penises as a result
of adopting a more monogamous reproductive strategy than their early human
ancestors. Those ancestors may have used penile spines to remove the sperm
of competitors when they mated with females. However, exactly how this change
came about is not known.
The researchers did not set out to study penile spines. Rather, they were
looking for chunks of DNA that had been lost from the human genome but not
the chimp genome, so they could then try to pinpoint what those chunks did.
The approach differs from that in most studies, explain Bejerano and
Kingsley, in looking at what has been deleted from the human genome rather than
what is present. "In the case of our study, had you started from the human
genome, there would be nothing there to see," says Bejerano.
They first systematically identified 510 DNA sequences missing in humans
and present in chimps, finding that those sequences were almost exclusively
from the non-coding regions of the genome, between genes. They then homed
in on two sequences whose absence in humans they thought might be
interesting -- one from near the androgen receptor (AR) gene and one from near
a gene
involved in tumor suppression (GADD45G).
Inserting the chimpanzee sequences into mouse embryos revealed that the
former sequence produced both the hard penile spines and sensory whiskers
present in some animals. The latter sequence acted as a kind of brake on the
growth of specific brain regions -- with the removal of its function
appearing to have paved the way for the evolution of the larger human brain.
"The goal of the project was to find molecular lesions [losses] that
underlie human evolutionary traits, with the examples illustrating different
aspects of the principle," says Kingsley.
"Until we looked at where the DNA was expressed, we had no idea which
switch -- if any -- it would actually control," adds Bejerano.
Other molecular biologists praised the work for its clever approach and
said it would open up new avenues of inquiry, particularly for those working
on the evolution of the human brain.
"As so often with very good ideas, it seems almost obvious in hindsight,"
said Svante Pääbo, who directs the genetics department of the Max Planck
Institute for Evolutionary Anthropology in Leipzig, Germany, and was part of
the team that recently sequenced the Neanderthal genome. "Since two of the
almost 500 deleted sequences they identified turn out to be interesting, I
am sure that several other ones on their list will turn out to be
interesting too," he added. The researchers are continuing to analyze the
remaining
508 DNA sequences."It is detective work and a great reminder that, in the
course of evolution, information is both gained and lost," said Sean
Carroll, an expert in animal genetics and evolution at the University of
Wisconsin, Madison.
David Haussler, who studies the molecular evolution of the human genome at
the University of California, Santa Cruz, added that our ancestors' loss
of penile spines is our gain today."Couples everywhere can be thankful that
this particular piece of DNA was ditched," he says.
http://www.scientificamerican.com/article.cfm?id=how-the-penis-lost-its-spik
es&WT.mc_id=SA_DD_20110310
Israel should not be fearing world opinion. Israel should be making the world fear (respect) her!!! And remember, it is the rich oil cartels who rule the world, NOT the Zionists!!
Mech'el B. Samberg
http://groups.yahoo.com/group/ProJewishProZionistGroup/?yguid=368134690
http://launch.groups.yahoo.com/group/stillnotjustmusicanymore/?yguid=368134690
http://groups.yahoo.com/adultconf?dest=%2Fgroup%2Fwhateverreturns%2F%3Fyguid%3D368134690
http://groups.yahoo.com/group/shieldofdavid/?yguid=373549731
Permission granted to share with others!!
**COPYRIGHT NOTICE**
In accordance with Title 17 U.S.C. Section 107,
any copyrighted work in this message
is distributed under fair use without profit or payment
For non-profit research and educational or criticism purposes only. http://www.law.cornell.edu/uscode/17/107.shtml
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Music we send is from our personal collections.
We are sharing it with you for your listening pleasure.
Please support the Artists by purchasing their albums.
Thanks for being part of "PoliticalForum" at Google Groups.
For options & help see http://groups.google.com/group/PoliticalForum
* Visit our other community at http://www.PoliticalForum.com/
* It's active and moderated. Register and vote in our polls.
* Read the latest breaking news, and more.
No comments:
Post a Comment