The Green Beard Model
In this model, Dawkins shows that the alleles of genes are quite selfish; that each of them is interested only in the number of copies of itself that it can pass on to the next generation and not the number of copies of other genes in the genome, of which it is a part, that are passed on to the next generation. Let’s imagine Dawkins’ hypothetical green-beard allele, which leads to the formation of a green beard in its carriers and also leads them to assist other “green-beards”. It can be seen (and it’s very easy to demonstrate on a mathematical model) that such a green-beard allele has a much greater chance of spreading in evolution than an allele that would lead its carriers to help their blood relatives. The carriers of green-beard alleles will pass (and will help to pass) on to the next generation more copies of themselves than copies of other alleles. On the other hand, an allele that would lead its carriers to assist blood relatives will be worse off, even though it would objectively ensure that a greater percentage of all the alleles (of all the genes) of its carrier are passed on to the next generation. However, it would not ensure that carriers of itself would be amongst them more frequently than the carriers of alternative alleles occurring on the second copy of the same chromosome. The unrelenting laws of biological evolution thus mean that each allele will behave quite selfishly and will be completely indifferent to the fates of the other alleles on the same chromosome or in the same genome. The only thing that it will count will be the number of copies of itself that it passes on to the next generation.