Why redhead finches have more sons

[depakid]

Decisions, decisions .... a female Gouldian finch chooses between black and red males.
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WHICH one will she choose? The fiery redhead or his black feathered rival? Looks count a lot to the pretty female finch on the lower perch. Given a choice, there is no question. She will go for her own kind, mating with the male with the same head colour as her - black. But if a redhead is her only option, she will do something extraordinary, Sydney scientists have found. She will produce many more sons than daughters after mating.

The research is the best evidence yet that birds can control the sex of their offspring. With the help of some black dye, to cover up the red and trick the females, the researchers also showed the female Gouldian finches determined their offspring's sex based on the male appearance alone. When black females thought they were mating with black males they had about equal numbers of sons and daughters.

A Macquarie University biologist, Sarah Pryke, said there was no chemical or genetic interaction between the parents at work. "Change the colour of the male's head with dye and the sex ratio changes." She said her team's study raised the question of whether other animals, perhaps even humans, have this ability to influence whether boys or girls are born.

"This discovery will change our understanding of sex determination across the animal kingdom," said Dr Pryke, whose study is published in the journal Science.

More: http://www.smh.com.au/environment/why--redhead-finches-have-more-sons-20090320-93p0.html

[rfranklin]

1. Yes, but how can humans have more red headed girls?

That's the important question.

[floridablue]

2. And how can humans meet more red headed girls ?

[Laelth]

3. That's very interesting.

Eventually, scientists will prove a theory I've been nurturing for some time. Greater sexual activity creates more females. The pseudo-scientific basis for this theory is that male sperm take longer to develop. As such, males who "store" their semen are more likely to produce more viable male sperm and increase the likelihood of male offspring. But males who have a lot of sex have less time to allow male sperm to develop and, thus, are more likely to have female offspring.

For the finches, all this study says to me is that the female is having sex more often with the finch she finds attractive (the black-headed one). She'll still have sex occasionally with the one she finds less attractive (the red-headed one), but the result will be that she has more male offspring.

I always gauge the sex lives of people I meet by the gender of their offspring. Families with lots of boys ... less sex. Families with lots of girls ... more sex.

This study is on its way to validating that theory, but the poor scientists quoted above don't seem to have put two and two together yet.

:dem:

-Laelth