14:04 23 February 04 Knowing whether a pregnancy will produce a boy or girl is not left up to chance for some mammals - UK biologists claim they have conclusive proof their offspring. It has long been known that many insects, birds and fish are capable of mammals has been controversial. American biologist Robert Trivers first their physical condition at the time of conception, and the idea has been debated for the 30 years since. adjustment in ungulates - herbivorous mammals with hoofed feet - and found a consistent pattern across the different species. Sons were produced in higher numbers by mothers who were in good condition and daughters were preferentially produced by mothers in poor condition," explains Stuart West at the University of Edinburgh, who carried out the study with Ben Sheldon from Oxford University. "In ungulate species, a few strong males control a large number of females, so only a small proportion of males get to mate, whereas most of the females will mate. "Therefore high quality females were more likely to undergo the greater demands of producing sons, as the sons were more likely to be of high quality and therefore have a chance of mating. Conversely, if maternal quality was poor, the ungulates produced daughters, since poor quality daughters had a greater chance of mating than poor quality sons," he told New Scientist. Read the rest at NewScientists http://www.newscientist.com/news/news.jsp?id=ns99994708 Comment: The reason for gender selection is not, as the article seems to imply (but the paper being reported probably doesn't), by a conscious decision by the mother but by a process of natural selection (of the trait to choose) that has a benefit to the herd. The mother receives no personal benefit whatsoever by the breeding success or failure of her offspring. Where the fittest females produce males and the rest produce females the herd's survival fitness is maximised. Mothers that are not maximally fit and produce males anyway, those males are less likely to breed and so less like to father females similar to their mothers. This seems to be an example of herd or group fitness with a single natural selection component acting on individuals. Note that there is no selection pressure on fit females that produce females. Of course the pivotal word in this article is 'quality'. By what criteria is 'quality' judged? Posted by Robert Karl Stonjek.