While the social constructivists may cry foul, there is an undeniable biological difference between males and females when it comes to the number of descendants they can leave behind. But in the real world, such a strategy can quickly unravel, and having more sons is not always a good thing. In the context of the experiment, where all sons were given access to a virgin female with whom they could mate, having more sons is obviously beneficial. Interestingly, the sons of multiply-mated females did not themselves produce more offspring – the difference in the number of grand-offspring came about solely because there were more sons available to become fathers. The researchers found females who mated with more than one partner produced significantly more grand-offspring, which the authors attribute to their having more sons in the first generation. The study went further and measured the offspring produced in the second generation. While the numbers of daughters the two groups produced was the same, promiscuous females produced 83% more sons than their monogamous contemporaries.
They found no difference in common measures of offspring fitness, such as size at birth or growth rate, but they did find that multiply-mated females had a higher proportion of male offspring that survived to adulthood. In their study Barbosa and colleagues allowed some females to mate with multiple males, and others to mate with only one, and then examined the offspring the females of both groups produced. Multiply-mated females produce more sons, which in turn, give their mothers more grandchildren. Andrews and colleagues – shows an unusual avenue to increased evolutionary prospects: boys. The new study – about to be published in the journal BMC Evolutionary Biology by Miguel Barbosa of the University of St. Either that or they might directly benefit by receiving gifts of food from their suitors (as in the case of charming gift-giving spiders). For some time, we’ve known that females can ensure they’ll receive high-quality sperm to fertilise their eggs if they mate with multiple partners.
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