"The tuatara (Sphenodon punctatus), found only in New Zealand, is the last surviving member of a distinct reptilian order Sphenodontia that lived alongside early dinosaurs and separated from other reptiles in the Upper Triassic."
The tuatara is so close to fossil forms that it has been dubbed a "living fossil". Animals like this were contemporary with dinosaurs. They are not typical reptiles. They have several uncommon physiological features:
"They have low body temperatures (they are active down to 5 deg C in the wild); slow rates of growth (about 50 cm in 35 years); a slow metabolism; a long generation time (sexual maturity at 10-15 years) and a slow reproductive rate (at 2- to 5-year intervals)."
Since slowness is a characteristic, it has been assumed that this is relevant to the lack of morphological change. "It has been argued that generation time, metabolic rate, body temperature and body size modulate the rate of neutral molecular evolution." This has led to an expectation that rates of neutral DNA sequence evolution also would be slow. So this is what the new research has tested.
Mitochondrial DNA has been used, taken from living animals and from sub-fossil bones ranging in age from 650 to 8750 radiocarbon years. The results were surprising:
"The rate estimates [. . .] show that the evolutionary rate of the tuatara HVR regions is the highest among the vertebrate species studied to date.This rate is >50% faster than that of other vertebrates."
[and, after exploring alternative explanations - ]
"These factors further confirm that there was minimal post-mortem damage to the DNA, that the ancient sequences obtained are authentic and that the unexpectedly high tuatara evolutionary rates are real."
The researchers have expressed some surprise at this finding. In their paper, they say: "Given this high rate of molecular evolution, the stable morphology of tuatara over tens of millions of years is remarkable." Their Press Release has this:
"Of course we would have expected that the tuatara, which does everything slowly - they grow slowly, reproduce slowly and have a very slow metabolism - would have evolved slowly," Lambert said. "In fact, at the DNA level, they evolve extremely quickly."
The paper points out that their findings challenge many hypotheses and notions about evolutionary change. The most substantial conclusion that can be drawn is that it supports the general hypothesis that the rate of molecular evolution is not coupled to the rate of morphological evolution. But this, of course, challenges the neoDawinian synthesis, which insists on small incremental changes acted on by natural selection.
The authors do not discuss the more fundamental question of how far DNA information is responsible for the form of organisms, or whether the form of organisms is determined by other information embodied in embryonic cells. This question is not being asked by Darwinists, who insist that all biological information must be traced back to the genome. However, some biologists (including those advocating Intelligent Design) are actively exploring alternatives.
"Previous studies on living fossils such as the coelacanth and the horseshoe crab have suggested a substantial nucleotide diversity in these phylogenetically distinct species, perhaps indirectly suggesting a high evolutionary rate."
The evidence is accumulating that much contemporary evolutionary theory is not supported by data. If you want a prediction arising out of the tuatara research, it is that the gulf between the genome and the development of form will widen, and the association of molecular evolution with morphological evolution will be weakened.
Rapid molecular evolution in a living fossil
Jennifer M. Hay, Sankar Subramanian, Craig D. Millar, Elmira Mohandesan and David M. Lambert
Trends in Genetics, March 2008, 24(3), 106-109.
Abstract: The tuatara of New Zealand is a unique reptile that coexisted with dinosaurs and has changed little morphologically from its Cretaceous relatives. Tuatara have very slow metabolic and growth rates, long generation times and slow rates of reproduction. This suggests that the species is likely to exhibit a very slow rate of molecular evolution. Our analysis of ancient and modern tuatara DNA shows that, surprisingly, tuatara have the highest rate of molecular change recorded in vertebrates. Our work also suggests that rates of neutral molecular and phenotypic evolution are decoupled.
Tuatara, the fastest evolving animal, EurekAlert, 20 March 2008
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