Sluggish Reptile Breaks Speedy Evolution Record

March 24, 2008 -- One of the world's most laid-back animals, the tuatara, may be the fastest evolving creature on Earth, according to a paper in this month's Trends in Genetics.

The lizard-like reptile's DNA changes naturally at a rate faster than has been observed in any other animal: 1.56 changes per nucleotide (DNA subunit) every million years.

The finding is particularly surprising in light of the fact that the tuatara, endemic to New Zealand, hasn't changed much physically since its ancestors hung out with dinosaurs 225 million years ago. Almost everything about the foot-long reptile is slow and easy.

Co-author David Lambert said the tuatara does all things slowly. He explained that "they grow slowly, reproduce slowly and have a very slow metabolism" when "in fact, at the DNA level, they evolve extremely quickly."

Lambert, a professor at the Allan Wilson Center for Molecular Ecology and Evolution at Massey University in New Zealand, now believes the rate of an organism's molecular evolution and the way it changes, or doesn't, over time are not necessarily connected.

"The processes that govern one are different than the processes that govern the other," he told Discovery News.

When scientists study an animal's rate of evolution, they usually compare one species to its close relatives. That was impossible for the tuatara, a "living fossil" whose close ancestors are all extinct. The reptile even looks like a mini dinosaur, with clawed feet and short spikes on its back.

For the study, Lambert and his team amplified and sequenced DNA from the bones of 33 ancient tuataras, dating from more than 8,750 years ago to 650 years ago, as well as blood samples from 41 modern individuals.