Research identifies lactose intolerance among early Europeans
UK and German researchers analysing DNA from Neolithic skeletons claim to have found the first direct evidence that early Europeans were lactose intolerant. The findings are published in the journal 'Proceedings of the National Academy of Sciences'. Today, over 90% of the population in northern Europe have the gene that enables us to digest milk. The gene is also present in some African and Middle Eastern populations, but is missing from the majority of the adult population globally. 'The ability to drink milk is the most advantageous trait that's evolved in Europeans in the recent past. Without the enzyme lactase, drinking milk in adulthood causes bloating and diarrhoea,' explains Mark Thomas of University College London, one of the research partners. Although the benefits of milk tolerance are not fully understood yet, it is believed that populations prospered who had a continuous supply of milk compared to the boom and bust of seasonal crops. Milk also has nourishing qualities and, unlike stream water, remains uncontaminated by parasites, making it a safer drink. 'All in all, the ability to drink milk gave some early Europeans a big survival advantage,' noted Dr Thomas. For some time, scientists have been aware that in the past, humans were unable to digest milk. However, no one was exactly sure when this change from being lactose intolerant to tolerant occurred. The researchers from UCL and the University of Mainz took samples of DNA from Neolithic skeletons dating back 5,840 and 5,000 BC. They found that the gene that controls our ability to digest milk was missing from the samples. 'Our study confirms that the variant of the lactase gene appeared very recently in evolutionary terms and that it became common because it gave its carriers a massive survival advantage. Scientists have inferred this already through analysis of genes in today's population but we've confirmed it by going back and looking at ancient DNA,' explained Dr Thomas. In addition to dating the evolution of lactose tolerance, the researchers also sought to challenge the theory that the ability to digest milk in some populations in Europe led to the spread of dairy farming. Instead, the researchers found that the lactose tolerance variant of the lactase gene only became common after dairy farming, which started around nine thousand years ago in Europe. Research will now continue to examine differences in tolerance levels in Europe. 'It's striking, for example, that today around eighty per cent of southern Europeans cannot tolerate lactose even though the first dairy farmers in Europe probably lived in those areas. Through computer simulations and DNA testing we are beginning to get glimpses of the bigger early European picture,' said Dr Thomas.
Countries
Germany, United Kingdom