Sex car?
The offended Eros will take revenge! Diemut Klarner, Süddeutsche Zeitung, 20.07. 2006 And so the water flea does it this way and that: The tormented and completely overwhelmed humanity can rightly ask itself: "What is sex actually for?" In a book worth considering, Christian Göldenboog has given some thought to the costs and benefits of dual gender. Even single-celled organisms do it, sometimes at least. They show that sex is not primarily about reproduction. On the contrary - after all, two cells initially merge into one. In order to multiply diligently, unicellular organisms do not need a partner - cell division is enough. Some species of sea anemones can also reproduce by dividing in half. Reproduction without sex is also widespread in the plant kingdom. Strawberries, for example, form long runners from which numerous shoots grow. While vertebrates never reproduce entirely asexually, some species of lizards exist exclusively as females. Offspring are formed by so-called parthenogenesis from unfertilized eggs. Nevertheless, the female lizards do not go without a love game - they stage it with their own kind. From a biological point of view, this autonomous version of reproduction has undeniable advantages. The females can pass on all of their genes to their offspring instead of just half because a partner contributes the other half. In addition, when males are involved, they must produce not only daughters, but also sons. Quite apart from all the troubles and dangers that have to be taken into account when looking for a partner and mating. The offended Eros will take revenge! So why do animals and plants usually come in two sexes? Molecular biologists as well as population geneticists and evolutionary researchers ask themselves this question. What they have found out so far is worth a good two hundred pages to the journalist Christian Göldenboog. Enough space for a multi-faceted picture that does not omit controversial aspects. However, the scientists agree on one point: The quintessence of sexuality is that the cards of the gene pool are constantly being reshuffled. Special sex cells are not absolutely necessary for this. Bacteria can become sexually active even without them, passing some of their genes on to distant relatives. For example, a harmless intestinal dweller that is insensitive to a certain antibiotic can pass this trait on to dangerous parasites. Where egg and sperm cells are involved, the possible combinations for genetic variants become immeasurable. But what evolutionary advantage is associated with such a willingness to experiment? Several years ago, the British zoologist William Donald Hamilton formulated the hypothesis that sex pays off primarily in the fight against infectious diseases. In the age of AIDS, that may sound like a bad joke, but on closer inspection it's entirely plausible. Because sexual reproduction means not putting everything on one card. Equipped differently, one or the other offspring may be well prepared when new pathogens appear. In an environment that is constantly changing, however, diseases are not the only challenges that need to be mastered with the appropriate genetic tools. Many plants, but also cnidarians, aphids and water fleas take a multi-track approach to reproduction. In addition to the complex model with two sexes, they also use simpler methods that produce less varied offspring. In contrast, in the majority of fauna, including mice and humans, the production of offspring is always associated with sex - or with fertilization in the test tube. The meager success rates in the cloning of mammals show that this coupling cannot be overturned so easily, even with the tricks of reproductive biology. This book discusses what is behind the relevant difficulties at the molecular level, as well as the molecular-biological roots of the battle between the sexes. Although far from any eroticism, the developmental background of love life certainly arouses emotions, which promises an exciting read. At times, however, the author tends to use misleading formulations: ¸¸In the case of birds such as the turkey and fish such as the salmon, it was possible to breed virgin species." What is meant are probably individual cases of successful parthenogenesis; they remain just as rare in salmon as in turkeys. In addition, the offspring that occasionally develop from unfertilized bird eggs are always male anyway. Admittedly, such blunders rarely make Göldenboog. In general, he appears to be highly read. Although he adopts a deliberately easy, conversational tone, he often overwhelms his readers with a flood of details - including the associated technical jargon. Not only in his interviews with prominent scientists, from which he likes to quote in detail, there are some hard-to-digest passages. If the author remarks at the appropriate point ¸¸When trying to understand meiosis, one can despair. Every biology textbook explains it in a different way in some way re way. You get confused," then he will probably reap approval. How egg and sperm cells develop is actually confusingly complicated. After all, the genetic inventory not only has to be divided evenly, but also reshuffled to illustrate more or less successful illustrations. Göldenboog, on the other hand, consistently dispenses with any pictorial representation. So the imagination is sometimes badly strained - a pity actually. CHRISTIAN GÖLDENBOOG: Why sex? From the evolution of the two sexes. Deutsche Verlags-Anstalt, Munich 2006, 239 pages, 19.90 euros.
