Sexual Selection - Sexual Selection As A Toolkit of Natural Selection

Sexual Selection As A Toolkit of Natural Selection

Critics of evolution have long challenged proponents to explain how animals initially evolved complex organs such as eyes, hands, or feathered wings. There is no doubt that, once developed, each of these organs offers major and obvious advantages. However, it can be difficult to imagine how certain organs' individual components each had distinct survival value at every stage in their evolution. One recent theory sees evolution as an "adventure quest" in which species develop complexity and novelty by acquiring modular capabilities through chance encounters in an evolutionary game. But, this still leaves open the question of how evolution initiated each module.

Geoffrey Miller proposes that sexual selection might have contributed by creating evolutionary modules such as Archaeopteryx feathers as sexual ornaments, at first. The earliest proto-birds such as China's Protarchaeopteryx, discovered in the early 1990s, had well-developed feathers but no sign of the top/bottom asymmetry that gives wings lift. Some have suggested that the feathers served as insulation, helping females incubate their eggs. But perhaps the feathers served as the kinds of sexual ornaments still common in most bird species, and especially in birds such as Peacocks and Birds-of-paradise today. If proto-bird courtship displays combined displays of forelimb feathers with energetic jumps, then the transition from display to aerodynamic functions could have been relatively smooth.