Evolution

Evolution

Allan Wilson died tragically of leukaemia at the height of his career. Born in Ngaruawahia, educated in New Zealand and then later for postgraduate studies and a faculty position at the University of Berkeley, Allan came to lead one of the most prominent and influential groups working in molecular ecology and evolution.

Extract from Allan Wilson’s obituary published in Nature, 353: 19, 1991

Allan Wilson (1934-1991) revolutionised the study of human evolution. The farm boy from Pukekohe completed his first degree at the University of Otago, but then moved to the University of California at Berkeley and soon became one of the most creative and controversial figures in post-war biology.

Wilson first came to world attention in 1967, when he argued in a paper published in Science, that the origins of the human species could be seen through what he called a ‘molecular clock’. This was a method of dating evolutionary change without using fossils, based on the idea that if two species diverged from a common ancestor at some point in the past, each lineage would have accumulated a number of mutations.

Wilson used this idea to study antibodies from humans and chimpanzees and found them to be almost identical, from which he deduced that early humans split from apes about five million years ago, much more recently than previously thought. Most contemporary anthropologists dismissed his work as absurd.

By the 1980s, as these findings were becoming more widely accepted, Wilson dropped another evolutionary bombshell with his ‘Mitochondrial Eve’ hypothesis. Using mitochondrial DNA,& which is passed on directly from mother to child, he announced in a 1987 paper that all modern humans could be traced back to one woman in Africa, who lived 150,000 to 200,000 years ago.

Wilson championed many radical ideas, such as his suggestion to use the genetic divergence point between head lice and pubic lice to determine when humans began to lose their ‘fur’. Wilson is the only New Zealander to receive a MacArthur Foundation fellowship, dubbed the ‘Genius Award’, and he was short-listed for the Nobel Prize when he died of leukaemia in July 1991.

Ancient history

Researchers at the Allan Wilson Centre for Molecular Ecology and Evolution, hosted by Massey University, continue to unlock the evolutionary secrets of humans, animals, plants and microbes.

David Lambert, at the University of Auckland, works with DNA from ancient or extinct species such as the moa. Using tiny fragments of moa DNA extracted from their bones, Lambert’s team was able to produce the first comprehensive phylogeny of moa and showed that the giant flightless birds displayed reverse sexual dimorphism – female moa were much larger than males.

Lambert’s team also extracted ancient DNA from colonies of Adelie penguins in Antarctica, making use of the fact that Adelies return to the same breeding sites each year to build their nests on top of the remains of generations that have gone before them. The oldest bones recovered are more than 44,000 years old and harbour some of the best-preserved ancient DNA. By comparing the ancient DNA with the genetic code of living penguins, the team was able to show that the birds’ rate of evolution was several times faster than previously thought.

Pacific voyagers

New Zealand was the last place to be settled, as part of a major voyage of expansion into the Pacific, which began around 3300 years ago. But just how exactly the ancestors of modern Polynesians, the Lapita, travelled from island to island has been a topic of intense scientific debate for decades.

While David Penny, at Massey University, is investigating changes in human DNA (mitochondrial DNA for female lineages and the Y-chromosome for males) in order to track the movements of ancestral Polynesian populations, his colleague Lisa Matisoo-Smith, at the University of Auckland, decided to study the best proxy, the Pacific rat or kiore. Kiore has many advantages: it doesn’t interbreed with other rat species that have made their way into the Pacific, there is plenty of material in faunal remains around ancient human settlements, and it is a lousy swimmer, so its only means of transport was a ride in the colonising canoes, most likely as a food source.

Matisoo-Smith has also been part of a team studying one of the oldest Lapita cemeteries ever found, at a coastal site on Vanuatu’s main island Efate. She managed to extract DNA from the 3000-year-old bones, which, if confirmed to be ancient DNA, would be the first glimpse of the genetic code of the intrepid seafarers who were the first to settle the remote Pacific.

Timeless Tuatara

Tuatara have watched dinosaurs evolve and die. They are the last surviving species of an ancient group of reptiles called Sphenodontia, and they survive today only because of the protection offered by predator-free islands. When Charles Daugherty’s team at Victoria University of Wellington discovered that temperature during incubation controls the sex of offspring, the researchers were able to develop techniques to hatch and raise tuatara in the laboratory, with much higher success rates. Hundreds of tuatara have since been returned to the wild, while the team continues to investigate their nesting behaviour, parasites and the genetics of the remaining wild populations.

By Veronika Meduna

Medals and awards

Allan Wilson: MacArthur Foundation fellowship

David Penny: FRSNZ, Rutherford Medal, Marsden Medal, CNZM

Charles Daugherty: FRSNZ, ONZM

Further reading and websites

Allan Wilson Centre for Molecular Ecology and Evolution website

Image courtesy of the Allan Wilson Centre

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