Genetic Errors Nixed Penis Spines, Enlarged Our Brains

[n2doc]

Genetic Errors Nixed Penis Spines, Enlarged Our Brains
By Dave Mosher March 9, 2011 | 2:44 pm | Categories: Evolution, Genetics

Geneticists have linked the physical appearance of humans to patches of DNA lost in the five million years since we shared a common ancestor with chimpanzees. One loss prevented men from growing penile barbs, which chimps possess. Another enlarged some regions of our brain.

“We can know what makes us human, what makes us physically different from other animals and why,” said developmental geneticist Gill Bejerano of Stanford University, an author of the March 10 study in Nature.

Bejerano’s team started by comparing the genomes of chimpanzees and macaque monkeys, which last shared a common ancestor 20 million years ago. They identified regions that hadn’t changed in chimps, then compared these to corresponding stretches of the human genome. They found more than 500 mutations known as deletions, or missing stretches of DNA, present in chimps but lost in humans.

Two deletions, one near a male hormone-signaling gene and another near a neural development gene, were especially intriguing. Tweaking those genes in mice suggested possible roles for the loss: eliminating penile spines and boosting cerebral cortex growth.

Bigger brains are an obvious advantage — “It probably helped us become the thinkers we are today,” Bejerano said — but it’s unclear why evolution weeded out the spines. These tiny, hair-like projections, found in male chimps and cats, can trigger female ovulation. They also increase sensitivity and remove existing sperm, ostensibly giving males a reproductive advantage. Bejerano suspects the spines are conducive to monogamy.

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http://www.wired.com/wiredscience/2011/03/deletion-human-evolution/

[d_r]

1. that has to be wrong

"Bejerano suspects the spines are conducive to monogamy."

No. Monogamy makes penile spines less necessary. Chimpanzees, especially bonobos, are notoriously randy. They have sex with each other any kind of way they can. Penile spines increase one male chimp's chances of winning the fertility bingo game and passing his genes on to a baby chimp by making it a little more likely the female will ovulate and by helping to remove the sperm of their competitors. Same thing for Tom cats. Humans not having them points to higher levels of monogamy for humans than for chimps. But we already know that by such things as proportion of the size of the testes.

[Peace Patriot]

2. Yeah, i puzzled over that, too. The article has to be wrong. The penile spines encourage polygamy.

It basically says so in the same paragraph--that the spines help remove a previous male's sperm. I think it's just a typo. Writer meant to write "polygamy" (not "monogamy").

[xchrom]

3. thank Darwin.

on the other hand -- there would be some very inventive flame wars here over penis spines -- i can well imagine.

[sofa king]

4. Which is why we put out for every Tom, Dick and Harry.

Yes, as a matter of fact I do know I'm going to Hell for that one.