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David Tyler: Rodents evolve – but does the evidence suggest phenotypic plasticity?

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File:Sicista betulina.jpg
birch mouse/dodoni


It is well known that rodents “evolve” fast. Archaeologists have used fossil vole remains as a means of dating because the different morphologies and species link to different time zones: this is the “vole clock”. So pervasive are these changes, it has become a matter of note when stasis is observed! A case in point is the birch mouse (genus Sicista). A “living fossil” at the generic level has been found in Inner Mongolia by Yuri Kimura, a doctoral student. It has been identified by its fossilised teeth – the only part of the animal still accessible for study. The teeth can be read like a book, with the cusps, valleys and ridges providing a signature by which the animal is known.

As far as chronology is concerned, the new fossil is said to be 17 million years old. Previous to this, the earliest fossil of Sicista was considered to be about 9 million years old. Whilst these figures are small compared with those obtained for the coelacanth, or the horse shoe crab, or the Wollemi Pine, they are large for rodents.

In a recent paper on the birch mouse,

… there is no discussion of how the observation of stasis contributes to a better understanding of stasis. The last sentence says little more than “The fact is fundamental to understanding the fact”. Darwinians commonly present everything in terms of adaptive evolution and refer to ‘stabilising selection’ or to a ‘lack of change in the environment’. Whilst this can pass as a reasonable hypothesis with the coelacanth and some other cases, it does not sound at all convincing when the stasis is the exception (as is the case with rodents) rather than an isolated case. This is where multiple working hypotheses are particularly valuable, so that we can weigh alternatives rather than trying to fit everything into a Darwinian framework.


Nope. there simply was more diversity in the past and this one survived extinction. There is no dating by these critters. iTs a error of geology. its not biology. without the geology there would not be these conclusions of biology. Thats why its strange to have old rodents still here. They are not old or from evolving trees of lineage. Just the survivors of massive diversity in the past. If something can last 17 million years without so much as even evolving sexier eyes then there's something wrong with evolution being behind biology period. Its unreasonable to reasonable people. Robert Byers

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