Nothing in biology makes sense except in the light of evolution
This famous aphorism is the title of a paper by Theodosius Dobzhansky (1973 Am Biol Teach 35:125-129), written in the context of a campaign to increase the quality of scientific education in the United States and liberate the biology class from the uninformed interference of the religious right lobby. Such a campaign is still needed, of all evidence. Evolution by natural selection is a necessary consequence of imperfect self-replicationa and is sufficient to account of all of life's diversity as we know it. As Darwin said so elegantly:
"As buds give rise by growth to fresh buds, and these, if vigorous, branch out and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications." Phylogenetics addresses the reconstruction of the Tree of Life. Speciation encompasses mechanisms by which reproductive isolation is developed, i.e., separation of branches into "fresh buds". (The Origin)
Evolutionary genetics focuses on the processes that lead to genetic changes in populations, i.e., growth of the branches.
Nothing in evolution makes sense except in the light of geneticsb
Unless one understands the underlying mechanisms of inheritance, one might be justified in thinking that evolution by natural selection is little more than wishful hand waving. Darwin deplored the absence of a theory of inheritance in the nineteeth century. He came up with an explanation that he himself considered less than perfect:
"I will try to persuade myself not to publish. The whole affair is much too speculative;" (Letter to Huxley)
Although the biological
community immediately embraced the idea of common descent, the process
proposed by Darwin (natural selection) was disregarded for decades for
lack of an understanding of inheritance. The Modern Synthesis was
the beginning of the integration of Mendelian genetics and
evolution. The integration of biology in an evolutionary
framework has continued at an accelerating pace with the discovery of
other evolutionary processes such as random genetic drift, symbioses,
developmental genetics, epigenetics, and continues incessantly.
aOnce you understand this statement, you will truly understand what evolution is all about.
bA variant of this statement (in the light of population genetics) is used as the official slogan in Michael Lynch's lab. Other versions exit.
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