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Monogamy is the only Option

Birds are the exception in the animal kingdom – 90 per cent of species enter into monogamous relationships. Monogamy in the animal kingdom is rare – because it is not essential for reproduction. So, why is monogamy found in so many species? At least 12 genes play an important role in mating strategies in the animal kingdom: some change partners, others mate for life or at least for a breeding season. Monogamy has emerged many times in the course of evolution, so monogamous species are found in every branch of the vertebrate family tree, spanning some 450 million years. Monogamy is evident and extant, however it is not easy to explain evolutionarily and biologically. Biologists at the University of Texas at Austin have examined the genetic underpinnings of complex bonding behavior. The team of researchers studied a total of ten vertebrate species.

They chose five monogamous species and one closely related but polygamous species. The five pairs of species consisted of a cichlid from the Lake Tanganyika in Africa, in which both parents operate brood care, as well as frog, mountain piper, Californian mouse and prairie vole plus the following unfaithful species: Cichlid, Strawberry Frog, tench, Deermouse and Meadow Vole.

Examining the genes.

in the proceedings of the US National Academy of Sciences, the authors defined a species as socially monogamous if they stayed together for at least one breeding season, raising their offspring together. Monogamy does not mean absolute fidelity in biology. In almost all monogamous species studied, including humans, other matings happen, explains study leader Hans Hofmann. The biologists each took three males of one species and examined the gene activity of the brain tissue. The result surprised the researchers: From fish to mice, they found 24 genes that were either up-regulated or down-regulated according to a very specific pattern. In monogamous species, there is a common pattern of gene activity, according to study author Rebecca Young, and it has been used again and again over 450 million years. This study brings us a step forward, confirms the evolutionary biologist Anna Lindholm of the University of Zurich, who was not involved in the study, Because we know little about the evolution of monogamy. In fact, monogamous behavior is not fully effective. Because of the different number of germ cells, there is a conflict of interest: males produce numerous sperm cells, females only a few eggs.

The most faithful species.

As a result, a male can have many more cubs by inseminating the eggs of many females with offspring - from an evolutionary perspective - the ultimate goal. In fact, males often compete for access to as many females as possible, while they are choosy. Only three percent of mammals share a pair bond and there are fewer in fish, amphibians and reptiles. An exception are birds, where 90 per centare loyal for at least one breeding season. Under certain circumstances, a solid partnership pays off: If partners are scarce or the offspring succeed only with the care of both parents. It's even more complicated. There are species, such as mice or lizards, that show a flexible mating behavior - where loyalty and infidelity are happening in close proximity, says Lindholm. Both variants have advantages and disadvantages. Thus unfaithful males produce more offspring. But the faithful who care for their families can be certain that the offspring are really theirs. When fish, frog and mouse developed monogamous behavior, they evidently resorted to the same set of genes found in the genome of all vertebrates. These genes are involved in the learning and memory processes. We have not shown that these genes cause monogamy, Hofmann emphasizes, but their interaction could control basic aspects of social behavior, such as tolerating specifics or recognizing the partner, paving the way to monogamy. The researchers want to test other species specific monogamy in the animal kingdom: Fidelity is the one option, Juliette Irmer expects chimpanzee and human beings are so similar so that monogamy is the rule.

Source: Treue ist die eine Option, Juliette Irmer, Frankfurter Allgemeine Zeitung, Feuilleton, Februar 10, 2019

-Aktualisiert am 10.02.2019-20:54, auch an Schimpanse und Mensch sei gedacht. bei uns ein ähnliches Genaktivitätsmuster finden lässt“, sagt Hofmann, „denn auch wir sind ein Produkt der Evolution.“

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