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Despite flash, males are simple creatures
Females evolve slower, but it's because they're more complex
 | Researchers find that males can respond quicker than females to sexual selection, resulting in glitzier garbs like the male peacock's tail feather, which outshows any drab peahen. |
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The secret to why male organisms evolve faster than their female counterparts comes down to this: Males are simple creatures.
In nearly all species, males seem to ramp up glitzier garbs, more graceful dance moves and more melodic warbles in a never-ending vie to woo the best mates. Called sexual selection, the result is typically a showy male and a plain-Jane female. Evolution speeds along in the males compared to females.
The idea that males evolve more quickly than females has been around since 19th century biologist Charles Darwin observed the majesty of a peacock’s tail feather in comparison with those of the drab peahen.
How and why males exist in evolutionary overdrive despite carrying essentially the same genes as females has long puzzled scientists.
New research on fruit flies, detailed online last week in the journal Proceedings of the National Academy of Sciences, finds males have fewer genetic obstacles to prevent them from responding quickly to selection pressures in their environments.
"It’s because males are simpler," said lead author Marta Wayne, a zoologist at the University of Florida in Gainesville. "The mode of inheritance in males involves simpler genetic architecture that does not include as many interactions between genes as could be involved in female inheritance."
The finding could also shed light on why diseases show up differently in men and women.
Complicated chromosomes
Wayne and her colleagues examined more than 8,500 genes shared by both sexes of the fruit fly Drosophila melanogaster. Of those genes, about 7,600 have different expressions (alleles) that do different jobs in males and females.
The flies were identical genetically, except for their sex chromosomes.
In flies and humans, thousands of genes made up of DNA are packaged into tiny units called chromosomes. Each parent contributes one set of 23 chromosomes to offspring, resulting in little ones with 23 father-given chromosomes and 23 mother-chromosomes — 46 total. One pair of these is called the sex chromosome. In this case, the females have two X chromosomes (XX) and males, XY.
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Many genes are found on the X chromosome, whereas few are associated with the Y chromosome. For female fruit flies, the X-chromosome genes can come in two flavors called alleles that not only interact with each other but also with other genes.
For instance, if one allele is dominant over the other, that allele would get "expressed" while the recessive allele would stay hidden. Though under cover, the recessive allele kind of hitches a ride on the X chromosome and can be passed on to future generations.
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