A research leader in the Centre for Comparative Genomics at Murdoch University, Prof Bittles has carried out comprehensive research in countries where cousin marriage is extremely common.
�Cousin marriage is popular in North Africa, the Middle East, Turkey, South India and Pakistan,� Mt Bittles said.
�In Pakistan between 50 and 60 per cent of people are first or second cousins,� he said. �I�ve studied data sets of up to five million people so it�s not as if we�re stabbing in the dark here.�
Prof Bittles became interested in studying this topic when he went to Bangalore for a research fellowship and discovered many people were married to their nieces.
�I just about fell through the floor I was so shocked,� he said. �I did a study over 10 years and we found that over 20 per cent of marriages in Bangalore in the �80s were between uncles and their nieces.
�More than 20 years later and Bangalore is now the IT capital of world so it can�t be all that harmful if you�ve got a highly successful society.�
Prof Bittles said the stigma around cousin marriage began in the mid-19th century and has continued.
�Gradually over the last 15 years it�s been accepted within the medical genetics community that the ill effects of cousin marriage have been overstated in the past,� he said.
�When you account for non-genetic variables like whether you�re educated or whether the mother is too young or too old then you find the estimates of the harm associated with first and second cousin marriage will decline and decline.�
The high percentage of people in Perth born overseas makes it difficult to pinpoint how many but Prof Bittles said there was a chance there was a number of people married to their cousins.
Prof Bittles said he wasn�t trying to persuade anyone to marry their cousins but the comprehensive research needed to be recognised.
He will give a talk �Why not marry your cousins, millions do?� for the Perth Probus Club at Lake Karrinyup Country Club on September 8.