4 Matching Annotations
- Jan 2023
In each case, a small population produced a star-burst of pioneers who permanently changed our way of thinking. Genius erupted in groups as well as in individuals. It seems likely that these bursts of creative change were driven by a combination of cultural with biological evolution. Cultural evolution was constantly spreading ideas and skills from one community to another, stirring up conservative societies with imported novelties. At the same time, biological evolution acting on small genetically isolated populations was causing genetic drift, so that the average intellectual endowment of isolated communities was rising and falling by random chance. Over the last few thousand years, genetic drift caused occasional star-bursts to occur, when small populations rose to outstandingly high levels of average ability. The combination of imported new ideas with peaks of genetic drift would enable local communities to change the world.
!- explaining human history : combination of cultural and biological evolution
Nature is forcing genetic drift to move faster in mating systems than in other bodily functions. If this is generally true, as Goodenough observes, it means that genetic drift in mating systems must have a special importance as a driving force of evolution. She proposes a general theory to explain the facts. In the big picture of life evolving over billions of years, established species with large populations evolve slowly and have a mainly conservative effect on the balance of Nature. The big jumps in evolution occur when established species become extinct and new species with small populations diversify. The big jumps, made by new species, are driven by genetic drift of small populations. For small populations to form new species, they must become genetically isolated. Rapid change of mating systems is a quick road to genetic isolation. Goodenough concludes that the rapid mutation of mating-system genes is Nature's way of achieving big jumps in large-scale evolution. Rapidly evolving mating systems gave us the diversity of species that astonished Darwin.
!- Ursula Goodenough : rapid evolution of mating genes
Kimura's theory explains the diversity paradox that puzzled Darwin. Why are we surrounded by such an astonishing diversity of birds and insects and microbes? From the point of view of Darwin, a small number of dominant species would have been sufficient. Kimura explains the mystery by invoking the power of genetic drift, which becomes suddenly rapid and effective just when it is needed, when small populations can vary fast enough to become genetically isolated and form new species.
!- solution to : diversity paradox - genetic drift
Sewall Wright, then 98 years old but still in full possession of his wits. He gave me a first-hand account of how he read Mendel's paper and decided to devote his life to understanding the consequences of Mendel's ideas. Wright understood that the inheritance of genes would cause a fundamental randomness in all evolutionary processes. The phenomenon of randomness in evolution was called Genetic Drift. Kimura came to Wisconsin to learn about Genetic Drift, and then returned to Japan. He built Genetic Drift into a mathematical theory which he called the Neutral Theory of Molecular Evolution.
!- Sewall Wright : genetic drift