But first, it is not clear how much is caused by natural variation only.
Previous studies had shown natural variation in GHC style - including palm-to-palm, wrist-to-wrist and forearm-to-forearm clasping.
He suggested it was possible that "natural variation" in the rate of cot death could be responsible for the vast improvements seen around the time the new advice was introduced.
Doubters for the most part are big fans of the medieval warm period, and see in the climate scientists' arguments an attempt to rewrite history so as to maximise the drama of today's warming and minimise the possibility that natural variation might explain the 20th-century record.
Recent studies show that there is substantial standing genetic variation in natural populations of planktonic organisms, which provides the raw material for natural selection.
But natural selection requires random variation to generate the various properties.
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The short answer is: calling into question whether the processes of random variation and natural selection are all we really need in order to understand the origin of species.
The team targeted the animals in their natural habitat to analyse individual variation and consistency in behavioural response.
Universal grammar allows for variation along a certain number of parameters, and this explains the grammatical variation we observe in natural language.
What we learn from these areas is precisely how evolution has acted to sculpt bodies, but it still does so using randomly-generated genetic variation and good old natural selection (and yes, Larry Moran, genetic drift also plays a role).
Natural selection should have pushed intelligence genes as far as they will go, so all variation should be environmental.
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Modern evolutionary biology as we understand it, which is to say variation via genetic drift, mutations, duplications combined with the pruning filter of natural selection, certainly explains a great deal.
So for Darwin to think that natural selection explains major evolutionary innovations, he had to bet on the amount and kind of variation that typically exists in lineages.
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