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Published online 7 January 2008 | Nature | doi:10.1038/news.2008.414
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Blind cave fish see the light
Two blind fish can make sighted offspring.
By mating blind fish from distant underwater caves, researchers have bred offspring that can see.
The results, published this week in Current Biology1, show that the two populations took different evolutionary paths to blindness.
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It is interesting that the authors use evolution for the loss of eye sight. Devolution seems a more appropriate description of the process. No sight has been gained where there was none in the past.
"Devolution" implies that evolution is inherently directional, which surely it isn't. If the starting point is a seeing population and selective pressures (or genetic drift) result in a blind population, that is still evolution. For all we know, there has even been a "gain" of something new, even if only at the molecular level, during the process of eyesight loss. Devolution would imply a backtracking of the process that led to sight; given that the different fish populations have different mutations, this is obviously not the case. The authors are right to use evolution.
The the article's summary does not reveal conditions of the experiment. Were the blind fish from the two areas kept in total darkness? If not, then the conclusions may be invalid. To fully test this, fish from the two areas must be kept in total darkness until the next generation can be examined, or fish from a single zone must be subjected to light. Instead of evolution or devolution, this may be a matter of gene deactivation rather than gene loss.