Sunday, 4 May 2008

The Dinosaur That Never Went Extinct

Tuatara. Image from Wikipedia

Joel Kontinen

The tuatara (Sphendon punctatus) is a spectacular reptile that only lives in New Zealand. Often called the living dinosaur, the tuatara has resisted both extinction and change. The tuatara is the only survivor of the reptilian order Sphehodontia. Evolutionary biologists believe that it lived together with early dinosaurs in the Upper Triassic some 200 million years ago.

Recently, researchers found an interesting detail about the tuatara. David Lambert and his colleagues at the Allan Wilson Centre for Molecular Ecology and Evolution analysed DNA sequences they found in the bones of tuatara estimated to be 8000 years old.

They published their findings in the journal Trends in Genetics. As reported by EurekAlert and LiveScience, their discoveries were astounding: they found that the tuatara is the fastest evolving animal. “What we found was that the tuatara has the highest molecular evolutionary rate anyone has measured,” professor Lambert says according to EurekAlert. Lambert’s study suggests that the tuatara has been evolving faster that animals like the cave bear, lion, ox or horse.

So how can an animal that has shown no signs of change for aeons be changing faster than many others? Professor Lambert says, “the rate of molecular evolution was uncoupled from the rate of morphological evolution.” In other words, inner change or change at the molecular level does not correspond to what we see on the outside.

Yet evolutionary theory predicted that slow change or no change would have corresponded to slow change or no change at the molecular level. Far from supporting the neo-Darwinian theory of molecules-to-man evolution, the “living dinosaur” shows that there are grave problems with the view.

Like other living fossils such as the crocodile, army ant, cockroach, Coelacanth and horseshoe crab, the tuatara is evidence for resistance to the type of change that Darwinian evolution desperately needs.

Some animal species have a history of incredible change. The dog (Canis lupus familiaris), which according to Linnean classification belongs to the same species as the gray wolf (Canis lupus), is capable of an enormous amount of variety, brought about by artificial selection. But this is not the kind of change that evolution in its neo-Darwinian sense requires.

And neither is the variety evident in the DNA of a reptile that has resisted change for a very long time.

I recently wrote about the horseshoe crab, another living fossil. You can read the post here.


Fastest Evolving Creature is 'Living Dinosaur'. LiveScience 26 March 2008.

Tuatara, the fastest evolving animal. New DNA research has questioned previous notions about the evolution of the tuatara. EurekAlert 20 March 2008.