Sex car?
Sex alone is also fine Manuela Lenzen, Frankfurter Allgemeine Zeitung, 01/22/2007 Life could be easier if we treated it like the freshwater polyp Hydra: A bud grows from the body of the parent animal, which ties itself off and becomes its own little polyp. Hydra reproduces asexually. Or the parasitic wasp: its offspring develops from an unfertilized germ cell, the parasitic wasp practices parthenogenesis, virgin procreation: there is only one sex, and the offspring of each individual are its clones. There is no parthenogenesis in mammals, they indulge in bizarre forms of sexual reproduction. Not everything has been said about them, not even everything is known. According to the evolutionary maxim that the individual is always concerned with transferring as many genes as possible to the next generation, sex should not even exist. After all, the sexually conceived offspring only carry half of their own genes. Is sex an inexplicable luxury, the product of random mutation? The journalist Christian Göldenboog spoke to leading experts in evolutionary research about these and related questions and made an informative and amusing book out of the conversations and background material ("Why Sex?". From the Evolution of the Two Sexes. Deutsche Verlagsanstalt, Munich 2006. 239 p ., born, 19.90 [Euro]). Clones, he has the biologist John Maynard Smith explain, have a major disadvantage: a virus that overcomes the immune system of an individual can, in the worst case, destroy the entire population. The combination of genes from two individuals in the complex processes of mitosis and meiosis, on the other hand, makes for unique individuals. If an immune system is outwitted, the virus can fail on the neighbor. Sex is diversity, and diversity is required: in defense against microscopic invaders as well as in adapting to diverse environments. In addition, this theory answers the question of the benefits of men: "In terms of the future continued existence of my own sex within the human species, I now feel much more comfortable. After all, you can tell people that we men are needed for health," quotes Göldenboog Evolutionist Hamilton. The whole thing probably came into the world with a procedure called bacterial sex, in which bacteria exchange parts of their genetic material without being able to call them male and female. Göldenboog explains why the egg cell is so much larger than the sperm cell and uses Amotz Zahavi's handicap principle to tackle seemingly nonsensical status symbols such as deer antlers and peacock feathers. According to the basic idea, anyone who can acquire a piece of jewelry that is a hindrance shows what a strong guy he is. The genes that are rearranged during sex are not interchangeable building blocks. Imprinting is the name of the phenomenon that worries the researchers. The genes are given a kind of molecular label that determines whether the paternal or maternal copy is activated. In mice, the maternal chromosomes are often active in brain areas associated with perception and conscious thought, and the paternal ones in the hypothalamus, where sex, eating, and aggression are involved. "When we humans are like mice, we run around with our mother's thinking and our father's whims," says Matt Ridley in Göldenboog's book. On closer inspection, the process that used to be quite harmless in school lessons as reduction division and in which the complete set of chromosomes in a cell becomes two cells, each with half a set, turns out to be incredibly complex. It's like two blind men looking for their socks that ended up in a single bag by mistake, the author quotes cell biologist Kim Nasmyth, who offers a surprisingly simple solution to the problem. With all the confusion surrounding processes that were believed to have been understood for a long time, it is hardly surprising that even the inheritance of acquired characteristics, long reviled as "Lamarckism", is being discussed again: a not really understood inheritance mechanism above the genes. "And this would indeed be an inheritance system that could react to environmental changes in the short term and that would be much more flexible than the Darwinian system," says Wolf Reik in an interview with the author. But: "There may be something completely different behind all this." What is clear, however, is that genes are not simply genes for something, but that their effects depend on the effects of other genes and on the environment. A gene can influence many traits, just as many genes can be involved in one trait. In the end, it's always about diversity: "There are mechanisms in nature that generate and maintain genetic diversity despite strong counteracting forces." In a changing world, no organism is perfect enough to serve as a cloning template for all. Because then all the potatoes will rot, like at the time of the Irish famine, then the meat producer has to compensate for the lack of resistance of the animals, which are the same everywhere but nowhere really adapted, with medicines. And so would sex.
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