How man, but not chimp, evolved to have spike-free penis

March 10th, 2011 - 11:36 am ICT by ANI  

London, Mar 10 (ANI): Sex would be a very different, not to mention painful, proposition had man not evolved to lose spikes that once existed on the male penis.

Researchers at Stanford University in California have found the molecular mechanism because of which man, but not chimps, macaques and mice, lost the spines on their penis.

The team 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 signalling.

“It is a small but fascinating part of a bigger picture about the evolution of human-specific traits,” Nature quoted Gill Bejerano as saying.

“We add a molecular perspective to a discussion that has been going on for several decades at least.”

The study also revealed a molecular mechanism for how we evolved bigger brains than chimpanzees and lost the small sensory whiskers that the apes have on their face.

The researchers 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.

They came down to two sequences that were absent in humans - one from near the androgen receptor (AR) gene and one from near a gene involved in tumour suppression (GADD45G).

When these chimpanzee sequences were inserted into mouse embryos, the mice developed 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.

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 worked well for humans today.

“Couples everywhere can be thankful that this particular piece of DNA was ditched,” he says.

The study appears in Nature. (ANI)

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