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New Evidence Found for One-Way Evolution

Posted on: Wednesday, 18 January 2006, 21:00 CST

Biologists at the University of California-San Diego say they've found new evidence to support an old idea: some evolutionary changes are irreversible.

The study involved tracing the 30-million year history of variation in a gene found in plants such as tomatoes and tobacco.

This is the strongest evidence yet to support irreversibility, said Joshua Kohn, an associate professor of biology who headed the study. If we had not used the genetic data coding for this reproductive mechanism and only inferred the pattern of evolution based on the traits of living species, we would have come to the opposite conclusion and with high statistical support that the trait evolved more than once.

The scientists examined existing variation in the gene used by many members of the Solanaceae family to recognize and reject their own pollen, which allows organisms to avoid self-fertilization and the harmful effects of inbreeding. This ability is sometimes lost, as is the case for garden tomatoes that can set seed by self-fertilization.

Apparently, once lost, the ability to reject pollen in order to prevent self-fertilization is never regained.

The research appears in the early online edition of the journal Proceedings of the National Academy of Sciences.

Source: United Press International

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