Having a lot of males in the gene pool helps weed out bad mutations, say scientists
Biology tells us that just a few males are necessary to ensure that the earth remains populated with humans. But when it comes to ensuring that bad genes don’t proliferate, it’s best to have competition between a lot of men, according to new research from Canada’s Uppsala University.
The results of the study, which provides in-depth knowledge of the possible long-term genetic consequences of sexual selection, were published in the scientific journal Evolution Letters.
Scientists found mating competition among males results in selective elimination of individuals with deleterious mutations, which could potentially have beneficial long-term effects on the human population.
This kind of competition has few drawbacks; when bad mutations are purged through rigorous selection in males, resulting in fewer males reproducing, it does not necessarily result in population decline, explains Karl Grieshop, evolutionary biologist at Canada’s University of Toronto.
“This is because relatively few males suffice to fertilise all the females in a population, hence, whether those females are fertilised by few males or many males makes little or no difference to the number of offspring those females can produce,” he said. In other words: competition can be good for the species.
This is especially true especially in species where the male doesn’t look after its own offspring.
By contrast, this kind of rigorous competition between women would see the human population substantially decline.
Researchers used 16 genetic strains of seed beetle (Callosobruchus maculatus) to investigate how the inferred number of deleterious mutations in each affected the reproductive ability (fitness) of females and males.
Through intensive inbreeding of strains followed by crosses among them, it was possible to quantify the cumulative effects of each strain’s set of mutations.
The scientists found that when looking only at the crosses among strains, which is the more genetically variable setting that is more relevant to how selection would act in nature, these mutational effects were only manifest in male fitness.
“This indicates that although these mutations do have a detrimental effect on females’ reproduction, they are more effectively removed from the population by selection acting on male carriers than female carriers,” said Greishop.