Australasian Science: Australia's authority on science since 1938

Evolution Goes Back to the Drawing Board

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What if snakes or whales could regrow legs, or chickens develop teeth, or humans re-evolve tails like our primate ancestors? Reversible evolution is possible under certain conditions – even after many millions of years – according to a study published in Evolution (http://tinyurl.com/zkdj5hy).

An international team of scientists found that some of the largest kangaroos ever to evolve resurrected crests on their teeth that were present in their distant ancestors more than 20 million years earlier. They speculate that changes in climate, habitat and diet provided the selection pressures that resurrected these dental features. As forests retreated towards the coastline over millions of years, kangaroos were forced to eat more grass, and their teeth needed to cut rather than grind their food.

Biologists have often discounted the potential for evolution to shift into reverse, dismissing such occurrences as cases of convergent evolution. However, co-author A/Prof Gavin Prideaux of Flinders University argues that “reanimating genetically mothballed features may be ‘allowed’ by evolution when it aligns with pressures that determine an animal’s ecology”.

PhD candidate Aidan Couzens found that “small changes to a ‘rule’ that determines how teeth form in the embryo have allowed some...

The full text of this article can be purchased from Informit.