In experiments with butterflies, evolutionary biologists from Leiden University have demonstrated that natural selection is not always the only factor which determines the appearance of an organism. Constraints also appear to play a role at times in determining the progress and outcome of the evolutionary process.
This research from Leiden provides evidence for the hypothesis of Stephen Jay Gould and Richard Lewontin. In 1979, these two scientists stated that Darwin`s theory of natural selection is often incorrectly seen as the sole factor which determines the outcome of evolution. Constraints also play an important role.
For example, constraints play a role in not allowing the development of eyes in the back of the head. Although decidedly advantageous, the evolution of eyes at this location will occur in few animals. This is due to limitations during the development and growth or because no variation for this trait is present in the genetic material. Another form of constraints occurs if two traits are linked to each other. A person with long arms always has long legs.
Michel Philippens | alfa
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