Promiscuity Prevents Extinction
Speaking of promiscuity, new research showed that wandering eyes may prevent extinction. Males are usually blamed for engaging in promiscuity, but in the vastness of the natural world, females are typically the ones with multiples mates.
According to research conducted by the Universities of Exeter and Liverpool, promiscuity reduces the risk of populations becoming extinct due to them being reduced to all-female broods because of a chromosomal mutation. This chromosomal disorder causes all Y-chromosome sperm to be killed before fertilization, resulting in a sex-ratio distortion. Female offspring become carriers of the SR chromosome, which can be passed on to their sons and daughters. Eventually, because the males are not able to reproduce and create male offspring, the population will turn all-female: a paradise for Sappho, but a nightmare for genetic evolution.
To test the ramifications of polyandry as compared to monogamy, researchers divided the common house fly into two sets. One set housed females that could have as many mates as they could handle; in the other group, the females were restricted to a single mate.
Over 15 generations, five out of 12 monogamous populations became extinct because of a lack of males, due to the spread of the SR chromosome, which was less prevalent in the populations with multiple mates. Having multiple partners greatly reduced the spread of the SR chromosome - males that carry the chromosome produce half as much sperm as those without it. Females with multiple mates are far more likely to be fertilized by a male not carrying the SR chromosome, because their sperm outnumbers the amount coming from SR-carrying males.
Source: Science Daily