Science Interviews

Darwin's Finches and Morning Sickness - Science Update

Chris - Now we're going to take our final trip to the States before the summer, where Bob Hirshon and Chelsea Wald will be looking at evolution in Darwin's finches and also why pregnant women get morning sickness.

Bob - This week for the Naked Scientists, the staff here at Science Update go out on a limb here in the States by throwing our support behind the controversial theory that life on Earth evolved by means of natural selection - a theory first proposed by foreign biologist Charles Darwin. In this episode, we'll learn about brand new insights into evolution from the finches Darwin studied. But first, scientists have long wondered why pregnant women get morning sickness. After all, they need all the sustenance they can get, so losing their breakfast doesn't seem to be the best course of action. But Chelsea tells us that there could be a good evolutionary reason for it.

Chelsea - When morning sickness strikes, pregnant women often ask, Why me? Well, they'll be happy to know that scientists at the University of Liverpool are working on an answer. By comparing 56 studies from 21 countries, they found that pregnancy sickness is more common in places with diets high in sugars, stimulants, vegetables, meat, milk, and eggs. Evolutionary psychologist Gillian Pepper says this may be the body's way of protecting the foetus from harm.

Gillian - These were the foods that perhaps when man was evolving, were more likely to contain pathogens, because if you don't have refrigeration, meat, milk, eggs could very quickly could become infected or go bad.

Chelsea - Women fared better in places with diets low in these foods and high in cereals and pulses such as beans, but Pepper doesn't recommend that pregnant women change their diets. Much more research is needed on whether doing so would reduce sickness or even be healthy.

Bob - Thanks, Chelsea. Scientists have now reported seeing evolution in action in none other than Darwin's finches. Two decades ago, large ground finches moved to a Galapagos island where medium ground finches lived. The problem was, the large finches ate the same seeds as the medium finches, and they did it faster with their bigger beaks. So scientists predicted that the medium finches' beaks would evolve to take advantage of smaller seeds. Princeton University evolutionary biologist Peter Grant says that happened during a drought two years ago.

Peter - The recent immigrant species had almost eaten the supply of food for themselves, so they almost went extinct. The resident species, a species that was there before the new species arrives, underwent this large shift towards small size in beaks.

Bob - He says this adds to the evidence that competition between species can lead to evolutionary changes.

August 2006