The second part of the book discusses sexual selection. Males compete with each other for the favour of the females. In many cases the females have a preference for males with a certain characteristic, for example large antlers, if we are talking about deer. The males with the largest antlers have the best chance to propagate and they get young ones with larger antlers than average (provided that this is a hereditary trait). In this way the giant deer (or Irish elk) could come into existence with a antler size of 3 m. One should say that bearing such heavy and wide antlers must have been a disadvantage, also because the animal could not stay in the woods. Still the advantage must have been greater than the disadvantage. Here it becomes clear that sexual selection and natural selection sometimes can work against each other. Know more? The giant deer

Another example of natural selection is the colourful face of the mandrill. Among the colourless ancestors of the mandrill there must once have been a specimen with a hereditary deviation, namely a colored mark in its face. The females were extremely interested in this male with the consequence that it could reproduce without problems. And his children had the same decoration as their father. After some generations all males had that coloured mark in their face. But the process of sexual selection went on and the females selected again and again the finest and most interesting male for mating. That's why the modern-day mandrill has such a beautiful face. Know more? The mandrill

Darwin 51

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