So I'm somewhat iffy on Theodosius Dobzhansky's take on evolution. As well as both, Godfrey Hardy and Wilhelm Weinberg. Can someone please briefly explain their theories or important contributions to the evolutionary theory?
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They did not propose different theories of evolution. These guys are geneticists and evolutionary biologists who worked to refine principles of evolution, especially in the area of mathematical predictions. Like all science, evolutionary biology and genetics have continued to be refined by later study. Hardy-Weinberg are famous for population genetics models and Dobzhansky did a lot of laboratory genetics confirming evolutionary principles.
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Dobzhansky published "Genetics and the Origin of Species", which amongst other things defined evolution as "a change in the frequency of an allele within a gene pool".
Using this definition Hardy, Weinberg, and the population geneticists who followed them came to understand that evolution will not occur in a population if seven conditions are met:
1. mutation is not occurring
2. natural selection is not occurring
3. the population is infinitely large
4. all members of the population breed
5. all mating is totally random
6. everyone produces the same number of offspring
7. there is no migration in or out of the population
H-W equilibrium can be expressed mathematically as
. p² + 2pq + q² = 1
In this equation, p² is the predicted frequency of homozygous dominant (AA) people in a population, 2pq is the predicted frequency of heterozygous (Aa) people, and q² is the predicted frequency of homozygous recessive (aa) ones.
An example could be
Time 1, p=0.4, q=0.6
Time 2, p=0.6, q=0.4
Time 3, p=0.4, q=0.6
Time 4, p=0.6, q=0.4
…
Time n-1, p=0.4, q=0.6
Time n, p=0.6, q=0.4
While with the given definition of “evolution” it is clear that evolution is occurring it is also clear that this sort of evolution will never produce a new species within the population group, let alone a complete new kind of organism.
This shows the weakness of this particular definition of evolution.
Using this definition Hardy, Weinberg, and the population geneticists who followed them came to understand that evolution will not occur in a population if seven conditions are met:
1. mutation is not occurring
2. natural selection is not occurring
3. the population is infinitely large
4. all members of the population breed
5. all mating is totally random
6. everyone produces the same number of offspring
7. there is no migration in or out of the population
H-W equilibrium can be expressed mathematically as
. p² + 2pq + q² = 1
In this equation, p² is the predicted frequency of homozygous dominant (AA) people in a population, 2pq is the predicted frequency of heterozygous (Aa) people, and q² is the predicted frequency of homozygous recessive (aa) ones.
An example could be
Time 1, p=0.4, q=0.6
Time 2, p=0.6, q=0.4
Time 3, p=0.4, q=0.6
Time 4, p=0.6, q=0.4
…
Time n-1, p=0.4, q=0.6
Time n, p=0.6, q=0.4
While with the given definition of “evolution” it is clear that evolution is occurring it is also clear that this sort of evolution will never produce a new species within the population group, let alone a complete new kind of organism.
This shows the weakness of this particular definition of evolution.