The smell of urine is an important criterion when choosing a partner
Scientists at the University of Liverpool, working under the guidance of Dr. Jane Hurst, have found that, all other things being equal, female mice prefer males whose urine contains a wider range of major urinary proteins (MUP). According to the results of earlier work by the authors, wild mice also avoid mating with their close relatives based on the recognition of these proteins.
The researchers concluded that female mice identify more outbred (which appeared as a result of mating unrelated individuals) males by the variety of urine proteins synthesized by them. More outbred individuals secrete a greater number of different proteins and the female chooses her partner according to the richest "bouquet" of his urine, without waiting for an opportunity to evaluate his physical characteristics in a fight with rivals.
Thus, the first evidence has been obtained that females can evaluate the "attractiveness" of males by signs that do not directly affect the health of animals. There is every reason to assume that this mechanism is widespread among other animal species.
Animals try to avoid inbreeding, which increases the likelihood of birth defects in offspring due to the transition of recessive genes with various defects to a homozygous state (the content of two identical copies of one gene in the genome). However, in spite of everything, this occurs in nature, and certainly more often than in human society (although it is quite possible that the prohibition of incest, which exists even among tribes that do not see a connection between sexual intercourse and the birth of children, has a biological, not social origin).
The authors wanted to check whether females would prefer stronger outbred males over inbred individuals and, if so, how the identification of more suitable partners occurs. To do this, they conducted a series of selective crosses, which allowed to create a line of mice that had no correlation between the heterozygosity of the genome as a whole and the heterozygosity of two gene clusters, allowing to directly assess genetic diversity using smell – an extremely diverse group of genes that both provide olfactory recognition mechanisms and include genes of the major histocompatibility complex (major histocompatibility complex, MHC) and the genes of the main proteins of urine. Heterozygosity of a gene means that there are two different variants of it in the genome, and the degree of heterozygosity of an individual at the genome level is a measure of inbreeding.
When additional sources of variation and competition were minimized, female experimental mice preferred males heterozygous for the genes encoding the main proteins of urine, ignoring such an important sign for health as heterozygosity for the genes of the main histocompatibility complex.
Thus, it turned out that females are sensitive not only to the degree of coincidence of the main proteins of the male's urine with their own (which avoids closely related crossing), but also to the degree of heterozygosity of this region in males. This makes the system of basic urine proteins an optimal tool for using genetic signals for the selection of partners in mammals.
Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily
28.04.2008