FRIDAY, 8 OCTOBER 2010
Recent research, published in Proceedings of the National Academy of Sciences , argues that theoretical models based on this principle are inaccurate. Using a large dataset of mutations in yeast, nematode worms and mice, the authors of the study found that most mutations affect only a small fraction of traits, and very few affected many. The analysis also gave the surprising result that the more traits a gene influences, the stronger its effects were on each trait.
Fisher's argument still holds true: there are lower frequencies of beneficial mutations in complex organisms. However, this can be overcome by a larger gain in fitness when a mutation is beneficial and a greater probability that it will become 'fixed' in a population. The overall outcome is that organisms with intermediate complexity have the optimal adaptation rates, and pleiotropy may even promote the evolution of complex forms.
Written by Robert Jones