25-year-old biologist and computer scientist Dr Simon Ho (BSc '03, MSc '04) is turning many longstanding beliefs about evolutionary dates on their head, thanks to his ground-breaking research into when the earth’s species diverged from their common ancestors. And his work is causing a revolution in the scientific world.

By rigorously examining the genetic code of creatures ranging from birds to mammoths and chimpanzees, Simon has shown that the rate at which species have mutated, as measured by DNA studies, appears to speed up over time. In other words, genetic differences seem to accumulate more slowly the further we look back along the evolutionary lineage of a species.

This claim contradicts the molecular clock theory which scientists have used widely since the 1960s and which says that the DNA mutation rate stays constant over time.

Simon’s time-bending breakthrough, the origins of which he traces back to a childhood passion for dinosaurs, dominated his doctoral research at Oxford University and was published in 2005 in the journal Molecular Biology and Evolution. Simon was awarded his doctorate in July 2006 for his thesis entitled ‘Estimating Rates of Molecular Evolution’.

His breakthrough has massive ramifications for evolutionary events, especially those that have occurred in the last two million years. For example, one important field of study affected by Simon’s theory is the search for the common female ancestor of all humans, sometimes called “mitochondrial Eve”.

“Using the molecular clock theory, which looks at the split between humans and chimpanzees, you get estimates of a common human ancestor evolving at about 150,000 to 200,000 years ago,” says Simon. “By correcting for the change in the rate of mutation, the result is significantly more recent than that, probably less than 100,000 years.”

Other events likely to change are the dates when humans first migrated from Africa, when animals were first domesticated and when the HIV virus first emerged.

Simon says his team at Oxford has now taken his theory on board, although it has caused widespread controversy and is generating continuing opposition from other scientists around the world.

Photograph by Ted Sealy

Page updated 23 Oct 06

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