In his book, Wonderful World, Stephen Jay Gould writes about an experiment of 'replaying life's tape', wherein one could go back in time, let the tape of life play again and see if 'the repetition looks at all like the original'. Evolutionary biology tells us that it wouldn't look the same the outcome of evolution is contingent on everything that came before. Now, scientists at the Instituto Gulbenkian de Cincia (IGC) in Portugal, New York University and the University of California Irvine, provide the first quantitative genetic evidence of why this is so.
In this study, to be published online this week in the journal Nature Genetics, Henrique Teotnio and his colleagues recreated natural selection in real-time, in the laboratory (rather than based on inferences from fossil records or from comparing existing natural populations) and provide the first quantitative evidence for natural selection on so-called standing genetic variation a process long thought to be operating in natural populations that reproduce sexually but which, until now, had never been demonstrated.
The researchers used laboratory-grown populations of fruit fly (Drosophila melanogaster), derived from an original group of flies, harvested from the wild back in 1975. These ancestral flies were grown in the laboratory, for two decades, under different environmental conditions, (such as starvation and longer life-cycles) so that each population was selected for specific characteristics. Henrique Teotnio and his colleagues placed these populations back in the ancestral environment, for 50 generations, to impose reverse evolution on the flies, and then looked at the genetic changes in certain areas of chromosome 3 of these flies.
Says Henrique, 'In 2001 we showed that evolution is reversible in as far as phenotypes are concerned, but even then, only to a point. Indeed, not all the characteristics evolved back to the ancestral state. Furthermore, some charac
|Contact: Ana Godinho|
Instituto Gulbenkian de Ciencia