Christmas Island DNA reveals its secrets
Genes are being used to understand more about the population of the tiny Australian territory of Christmas Island (Image: iStockphoto)
The inhabitants of multicultural Christmas Island originally came from southern China and Southeast Asia and have tended not to mate with people of European descent, new genetic research has found.
Molecular geneticist Dr Cheryl Wise, who was at Edith Cowan University in Western Australia at the time of the research, and colleagues report their study online in the American Journal of Physical Anthropology.
They say their findings may have implications when testing for inherited conditions more common in people from a particular ethnic background, like the blood disorder thalassaemia.
Wise and team studied DNA in blood samples from 100 people who were living on, or were born on, Christmas Island, the tiny Australian territory 360 kilometres south of the Indonesian capital Jakarta.
They studied differences and similarities in mitochondrial DNA (mtDNA), inherited from the mother, and Y chromosome variations, inherited from the father.
"Mostly Christmas Islanders have come from southern China and Southeast Asia like Malaysia and Thailand," says Wise, who is now at the Royal Perth Hospital.
The researchers found similar origins for both men and women.
Something old, something new
The findings confirm historical records of labourers recruited from China and Malaysia following the discovery of rich phosphate deposits on the island in the 19th century.
But the genetics study also tells the researchers something new: people of Christmas Island have generally kept to themselves and not bred with Europeans.
The 2002 census reports 61% of Christmas Island residents identified themselves as Chinese, 25% Malay and 14% European.
In people sampled by Wise and team, 75% were Chinese, 11% Malay and 6% European.
Wise says the sample was small but was meant to be part of larger study of migration and interbreeding patterns.
She says the variation between the mtDNA of people from different parts of Asia was not great enough to be able to tell if they mated with each other.
Public health implications
One implication of the new finding is that it helps health authorities to test for inherited disease-related genes.
One partner in the study was the Western Australian Centre for Pathology and Medical Research, which tests for thalassaemia, an inherited blood disorder common in some southeast Asian countries.
