Pushed To D Limits

An active female mounts a passive one, curves the tail under the other's body, strokes the partner's back and neck, joins genital regions, and rides on top for one to five minutes. The active female lizard always has small undeveloped eggs, while the passive female has large pre-ovulatory eggs. But there are cyclic variations in behavior and egg size in these reptiles, and roles reverse; the passive female of one encounter can be the active partner of the next. Says Crews: "We are now trying to determine whether this malelike behavior facilitates reproductive function." Translation: the psychobiologist does not yet know why the females mock the male-female behavior of related two-sex species. The eggs hatch with or without the lesbian courtship.

At the same time that it is continuing to lose genes, it's found some new ways of replenishing itself.The Y chromosome has been secretly creating backup copies of its most important genes. These are stored in the DNA as mirror images, or palindromes — which read the same way forwards and backwards. ("Madam, I'm Adam" is a famous example.)In Y chromosome palindromes, the first half contains the gene and the second half contains the same information, just in reverse.

Probably this helps us to explain why these genes have been able to persist despite millions of years of assault from random mutations. And, he says, it means the Y chromosome won't simply keep shrinking away until it disappears altogether.