Do Sexually Extravagant Males Age Faster?
Far too easily do we extrapolate results from animals to humans, especially if they make good copy. Consider the case of the houbara bustard. Males of this desert bird attract females through extravagant sexual displays. According to conventionally accepted versions of sexual selection, such displays are a signal to females that the most extravagant displays are made by males who are reproductively the ‘fittest’. Indeed when researchers tested the sperm quality of bustards, they found the more extravagant the display, the better the quality of sperm. But what was unexpected, according to a paper published in Ecology Letters, is that the very same males who perform the most extravagant displays also suffer from premature biological ageing and pass their reproductive prime earlier than less showy males.
According to the research: ‘Extravagant males were found to pass their reproductive prime much sooner than their more subdued rivals and they began to produce ‘burnt-out’, smaller ejaculates, containing high numbers of dead and abnormal sperm.’
‘Male houbara bustards may help to explain how senescence, or biological ageing, has evolved,’ concluded lead author Brian Preston from the University of Burgundy, France. ‘The bustard shows that an over-abundance of early reproductive effort comes at the cost of physiological declines later in life. This early versus late life trade-off can help explain why senescence occurs, and reveals the potential significance of sexual selection in explaining rates of ageing.’
It may well explain why in both bustards and humans, male life expectancy is lower than in females.
But much as we would like to believe older men in expensive sports cars suffer from low sperm count if not erectile dysfunction, it would be better to wait for the data to justify such a conclusion. Preston, though seems convinced, ‘This is the bird equivalent of the posers who strut their stuff in bars and nightclubs every weekend. If the bustard is anything to go by, these same guys will be reaching for their toupees sooner than they’d like.’