Do yu think you are sexy? It’s all thanks to our mom! Forget all stories about daddy’s superior genes, sex appeal is all due to a mother’s resource investment when we are still in the womb.
A Swiss-Australian research team lead by evolutionary ecologists at the University of Zurich has challenged the theory that females mate with superior males to obtain good genes for their offspring. They looked at Zebra Finches, those colorful and noisest birds.
As in most other bird species, Zebra Finches parentsb oth contribute to offspring rearing. The social partner of a female, however, is not always the biological father of the young. If the opportunity arises, females will choose to pair with partners other than their primary mate – with the interesting result that the offspring of different fathers have different qualities. And, as evolutionary ecologists from the University of Zurich and biologists from Macquarie University in Sydney have discovered, offspring sired by an extra-pair partner develop larger color ornaments and are more attractive to females than their social half-brothers.
Females were believed to engage in extra-pair copulation with genetically superior males to obtain better genes for their offspring. Barbara Tschirren, professor for evolutionary ecology at the University of Zurich, and her team have challenged the idea of the exceptional male. In a study published in «Proceedings of the Royal Society» the researchers demonstrate that – despite the observed quality differences – the fathers of attractive sons are neither better looking nor genetically superior: the enhanced ornamentation of sons is due to the mother’s investment in the eggs.
It’s first-laid eggs what receive the best treatment, which gives them a higher chance of survival. This seems to trigger a strong competition among males to fertilize these valuable eggs early in a female’s laying sequence. The Univeristy of Zurich professor hypothesizes that sperm competition might decide the battle, with males with faster sperm being able to fertilize the most valuable eggs.