MALE obsession with size appears to be universal. Male sexual traits that are attractive to females of the species, such as antlers or a peacock鈥檚 feathery display, become disproportionately large as body size increases.
Most body parts grow in proportion with each other as individuals of a species become larger, but it has long been known that the visual markers of reproductive prowess are a special case. Now, in the largest survey to date, James Brown of the University of New Mexico in Albuquerque and his colleagues have examined the proportions of 284 ornament-bearing species to see whether the tendency is truly universal. They found that in virtually every case, the trait grew by roughly the square of the overall growth rate. It made little difference whether the trait functioned as a weapon or an ornament (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0602994103).
Even for purely decorative ornaments, dedicating energy and nutrients to growing larger ornaments rather than overall body size makes good evolutionary sense, Brown says. Extra-large ornaments are more effective at attracting females than a slightly larger body. 鈥淚t indicates that the male with the bigger trait had more resources,鈥� Brown says.
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