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User:TonySidaway/Evolution (view source)
Revision as of 20:19, September 7, 2012
, 20:19, September 7, 2012→Population thinking: Moving away from Plato
By the early nineteenth century fossil collecting had spread widely enough to make the recognition of a succession of different forms of life to be a commonplace. Many naturalists noticed that some of the fossils seemed to be extinct members of known species, though often of different size from any of their living relatives, or bearing characteristics unknown in the surviving species.
By the early nineteenth century fossil collecting had spread widely enough to make the recognition of a succession of different forms of life to be a commonplace. Many naturalists noticed that some of the fossils seemed to be extinct members of known species, though often of different size from any of their living relatives, or bearing characteristics unknown in the surviving species.
==Population thinking==
There were still barriers to thought, hurdles that prevented the understanding of common descent gaining ground. Chief among these was what might be called the platonic species concept. In this view of species, individuals are all members of one and only one species, and the range of variation of any species is quite small. This is expressed at a very strict form by the classical Greek philosopher [[Plato]], but it conforms to everyday experience and most people's instincts.
An alternative to this species thinking which is often adopted by modern biologists, is population thinking. A population is a group of organisms that interbreed. If river flooding or some other force should isolate some members of a population from others, then the members of the isolated group become a new population. Since descendants get their characteristics from their ancestors, this provides a coherent alternative to the platonic species concept. This new thinking allows naturalists to think about what happens to a population that is isolated in such a way? Does it mirror the population from which it is derived, or does it change? Could such change help to explain why organisms, both in the modern day organisms and fossils, appear so well adapted to their circumstances?