VI.3.7 Meiotic drive at work in the competition of sperms from a single male creates selection pressure for the emergence of polygamous reproduction systems.
In a great many species of animals, the female copulates with a larger number of males during reproduction. Simultaneously, the ejaculate from a single male should theoretically be sufficient for fertilizing all her oocytes. Consequently, some authors are of the opinion that the biological function of this female promiscuity lies in creating a disadvantage for males carrying an ultraselfish allele in their genomes, i.e. an allele that increases its content in the ejaculate through meiotic drive (Zeh & Zeh 1996). If such an allele damages the sperm that do not contain its copy (cf. t-haplotype for mice or SD-allele for Drosophila), then the particular male has reduced fertility and thus also reduced biological fitness. The fact that the female obtains sperm from several males increases the probability that her oocytes will finally be fertilized by sperm that do not carry the ultraselfish allele.