Why do the males of the species evolve faster than their companions? The mystery comes from this: males are simpler creatures.
In most species, males always seem to do brighter outfits, more alluring dances, and a more melodic voice in fights for a mate. The result of this so-called fertility selection produces a showy male and a hardy female. It seems that evolution has accelerated in males compared to females.
The idea for this dates back to the 19th century, when Charles Darwin observed majestic male peacocks compared to the stubborn tail of gray peacocks. Why and how men do this remains a mystery to scientists.
New research on fruit flies has shown that in males there are far fewer genes that prevent them from responding quickly to external stress than in females. “It’s because guys are simpler,” said lead researcher Marta Wayne, a zoologist at the University of Gainesville in Florida, US.
“The genetic model in males involves a simpler genome, not having as many genetic interactions as with female genetics.” The results may also explain why the disease manifests itself differently in women and men.
In the experiment, fruit flies were found to have identical genomes, except for the sex chromosome.
In fruit flies (as well as in humans), the genome is encapsulated in pairs of chromosomes, including the sex chromosome. In females the sex chromosome pair is XX, while in males it is XY. While the number of genes on the X chromosome is very large, on the other hand, there are only a few genes associated with the Y chromosome. Each gene usually has two versions, called alleles. In fruit flies, these alleles interact with each other and with other genes.
Since males only have one X chromosome, “what you see is exactly what you expect.” If a gene helps it to increase mating capacity, that gene will be selected to go further, and vice versa, if a gene is not good, it will be eliminated within a few generations. But in women, the confusing interactions between the genes of two X chromosomes and between the alleles of each of these Xs make it much more difficult to select and transmit good traits.
“Having a single X makes male genes more openly selected.”
The researchers noted that the results were not directly relevant to humans, as “the function of X in humans is different from that of fruit flies.” However, it also helps explain the difference between the rhythm and the response of men and women to disease.