The Evolution of Population Sizes and Humans

In 1973 the eminent evolutionary geneticist Theodosius Dobzhansky wrote an essay  entitled “Nothing in Biology Makes Sense Except in the Light of Evolution.” Presumably, that would include molecular biology, and as Dobzhanksy was writing, the field of molecular evolution was bearing fruit that would revolutionize our understanding of Darwinian evolutionary biology. Or, perhaps more precisely, it would extend and move beyond a purely Darwinian understanding of changes in the DNA sequence on the molecular level. In the 1970’s, the idea that evolution at the scale of DNA and proteins was “neutral” in relation to adaptive fitness came to the fore through the work of both population geneticists and molecular biologists. This is in contrast to the emphasis placed on natural selection and adaptation in Darwin’s original theory, and pushed forward by Dobzhansky and his colleagues in the mid-20th century with the Neo-Darwinian Synthesis. Today on the Unsupervised Learning podcast Razib talks to Alex Palazzo, a molecular biologist who has also thought deeply about the relationship between his field and evolution, and where we are 40 years after the neutralist revolution.

The conversation covers the issues brought up in Palazzo’s paper Non-Darwinian Molecular Biology. Was Charles Darwin wrong? Well, his ideas and theory were clearly incomplete in various ways. Palazzo argues for the importance of the mechanistic and structural details of genes and DNA that go into explaining why evolution produces the diverse traits and characteristics we see all around us. He also discusses why complex lifeforms exist due to the built-in tolerance of sloppiness in DNA replication, and addresses questions such as why genomes vary in size so greatly (did you know that the wheat genome is forty times larger than the rice genome?).