Evolution: Why Sex?

Although it provided the most revolutionary and successful explanation for the complexity of life hitherto proposed, Darwin's discovery of the process of natural selection also left a great number of unexplained phenomena ubiquitous in the plant and animal worlds, even if you ignore the question of how sexual reproduction arose in the first place: many organisms display features that seem to go against their survival needs.

Take the classic example of the peacock's tail: the larger it is, the more expensive it is to maintain and the easier it becomes for tigers to feast on them, yet peacocks consistently display these exuberant tails, which grow larger and more intricate by the generation, increasingly putting them at risk of becoming someone else's dinner. Darwin brilliantly solved this puzzle by proposing a second evolutionary mechanism: sexual selection.

For the past 150 years, and thanks to the theoretical foundation of sexual selection identified by Darwin, scientists have been putting together a fascinating and theoretically coherent picture of the rich and diverse sexual lives of animals (including humans), proposing, testing and confirming all kinds of insightful and useful hypotheses and principles, some of which are explored in today's documentary: sexual diversification, the red queen hypothesis, parental investment theory, paternal uncertainty, mate preferences, evolutionary psychology, and optimal mating strategies, all driven by the blind and relentless process of evolution.

Check out more about the fascinating lives of bonobos, or the sexual lives of the human animal, or the rest of this fascinating documentary series.

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