March 21 (UPI) -- Scientists believe wild animals, including cats, wolves and pigs, became more promiscuous as their population densities increased near human settlements. And according to researchers at the University of Liverpool, this shift in reproductive behavior paved the way for domestication.
"As population density increased, males encountered mating opportunities more frequently, and the benefits of pursuing these likely outweighed the costs of attempting to defend exclusive access to females," biologist Paula Stockley said in a news release. "Polyandrous mating therefore often increased with high population density."
Among males, an increase in promiscuity provided a boost in sperm production and quality, while females benefited from improved fitness and by avoiding the consequences of unwanted advances.
Stockley and her colleagues hypothesized that such a boost in sperm quality and genetic health would have allowed more promiscuous lineages to crowd out their wild counterparts.
"It follows that if early domestic females mated with multiple males, both wild and domestic, the more abundant and higher quality sperm of the early domestic male would out-compete the sperm of wild males," Liverpool archaeologist Ardern Hulme-Beaman said. "This could explain the reduction in transfer of genes between wild and increasingly domesticated populations."
In their new paper on the subject, published this week in the journal Biology Letters, scientists argue this shift in sexual patterns could explain changes in social behavior among animals living closer to human settlements.
While researchers acknowledge that habitat preference and selection by humans likely played dominant roles in driving animal domestication, additional investigation of shifts in mating behavior could improve scientists' understanding of the domestication process.