Horizontal gene transfer at the basis of natural evolution

A P2P correction to Darwinian theory?

Excerpts from an extensive treatment by the New Scientist, from Mark Buchanan:


“JUST suppose that Darwin’s ideas were only a part of the story of evolution. Suppose that a process he never wrote about, and never even imagined, has been controlling the evolution of life throughout most of the Earth’s history. It may sound preposterous, but this is exactly what microbiologist Carl Woese and physicist Nigel Goldenfeld, both at the University of Illinois at Urbana-Champaign, believe. Darwin’s explanation of evolution, they argue, even in its sophisticated modern form, applies only to a recent phase of life on Earth.

At the root of this idea is overwhelming recent evidence for horizontal gene transfer – in which organisms acquire genetic material “horizontally” from other organisms around them, rather than vertically from their parents or ancestors. The donor organisms may not even be the same species. This mechanism is already known to play a huge role in the evolution of microbial genomes, but its consequences have hardly been explored. According to Woese and Goldenfeld, they are profound, and horizontal gene transfer alters the evolutionary process itself. Since micro-organisms represented most of life on Earth for most of the time that life has existed – billions of years, in fact – the most ancient and prevalent form of evolution probably wasn’t Darwinian at all, Woese and Goldenfeld say.

Strong claims, but others are taking them seriously. “Their arguments make sense and their conclusion is very important,” says biologist Jan Sapp of York University in Toronto, Canada. “The process of evolution just isn’t what most evolutionary biologists think it is.”


“Simulations suggest that horizontal gene transfer allowed life in general to acquire a unified genetic machinery, thereby making the sharing of innovations easier. Hence, the researchers now suspect that early evolution may have proceeded through a series of stages before the Darwinian form emerged, with the first stage leading to the emergence of a universal genetic code. “It would have acted as an innovation-sharing protocol,” says Goldenfeld, “greatly enhancing the ability of organisms to share genetic innovations that were beneficial.” Following this, a second stage of evolution would have involved rampant horizontal gene transfer, made possible by the shared genetic machinery, and leading to a rapid, exponential rise in the complexity of organisms. This, in turn, would eventually have given way to a third stage of evolution in which genetic transfer became mostly vertical, perhaps because the complexity of organisms reached a threshold requiring a more circumscribed flow of genes to preserve correct function. Woese can’t put a date on when the transition to Darwinian evolution happened, but he suspects it occurred at different times in each of the three main branches of the tree of life, with bacteria likely to have changed first.” an

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