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Living dinosaur found to be fastest evolving creature

Researchers in New Zealand have found that the Tuatara, a lizard native to the …

How fast can a creature evolve? While evolution has no ultimate direction, the DNA of some creatures are changing faster than others. As described in this month's edition of Trends in Genomics, a team of New Zealand researchers have found the fastest evolving vertebrate known to date: the Tuatara.

The Tuatara, Sphendon punctatus, is essentially a living relic of the age of the dinosaurs, found only in New Zealand. It is the last living species in the order Sphenodontia. The creature's lineage split off during the Upper Triassic, about 220 million years ago—meaning that early tuataras lived along side the dinosaurs. It resembles a lizard in appearance, yet it is equally related to both lizards and snakes. Due to this unique phylogeny, it is a species of great interest to those who study the evolution of reptiles.

According to researchers, the tuatara does everything slowly—it moves slowly, it metabolizes food slowly, it reproduces slowly—but it is changing at the molecular level at a rapid pace. By examining genetic material from tuatara bones dating to around 8000 years ago, the research team, led by Professor David Lambert, found that the tuatara is evolving at an average rate of 1.56 substitutions per nucleotide per million years. This measurement puts it above the previous fast-evolving record holder, the Adelie penguin.

When the tuatara is compared to other rapidly evolving species, its small change in morphology is quite remarkable. Other mammals and birds with similarly fast rates of nucleotide substitutions have undergone huge changes in appearance in similar time frames. This rapid change at the genetic level is not what one would expect for a creature that's retained its appearance for millions of years, but it does offer up experimental evidence for a decades-old theory that suggested that the rate of morphological evolution is decoupled from the rate of molecular evolution.

According to the authors, this paper shows that physiologic parameters alone cannot explain the differences in rates of molecular evolution between species. The authors have measured the evolution rates of various species, and hope to extend their work to see how fast humans are evolving. According to Prof. Lambert, "There are human mummies in the Andes and some very good samples in Siberia where we have some collaborators, so we are hopeful we will be able to measure the rate of human evolution in these animals too."

Trends in Genomics, 2008. DOI: 10.1016/j.tig.2007.12.002

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Channel Ars Technica