Tuesday, January 10, 2012

Females can manipulate gender of their offspring

It has long been thought that males determine what gender their offspring will be. Male sperm cells either contain an X or a Y chromosome, while women only pass on an X chromosome. Because the combination XY results in male, and XX in female, there does not seem to be much a female can do to make more daughters, for example. Research from the University of Exeter, however, points in an other direction. They have shown that 'strong' females have the capability to tilt the balance towards making more female offspring.

The findings are part of an ongoing competition between male and female bees. However, the scientists claim it is likely we will find the same mechanism in other animals. In the bee world, strong males with big jaws are more successful in mating with a female. Because of their masculine genes, any female offspring will be regarded as weak, and will produce more male offspring. However, weak males produce stronger female offspring, which in turn give birth to more female descendants. Their findings show that parent strength is a determining factor in gender outcome for offspring. Strong males will grandfather more males, while strong females will have more daughters than sons.

The ongoing battle between males and females is part of an evolutionary struggle. It has been hypothesized for many decades, amongst others by the great biologist Richard Dawkins, that male and female genes struggle to compete with each other. Because male genes will attempt to 'beat' the female ones, and vice versa, it is perhaps not surprising that strong animals can influence their offspring's gender.

It was previously thought that gender is determined solely by whether the male passes on the X or Y chromosome. However, it seems that there are genes influencing the outcome, something of which we are just beginning to discover the genetic basis. It is currently unknown whether humans possess such genetic mechanisms, but it is likely we carry them as well.

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