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Africans' ability to digest milk linked to spread of cattle raising
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[QUOTE]Originally posted by Troll Patrol # Ish Gebor: [QB] [i]Tishkoff's team estimates that the most successful of the African lactose tolerance mutations arose within the last 7000 years and quickly spread through dairying populations.[/i] [QUOTE] [b]Got lactase?[/b] In the US and many other countries, we've certainly "got milk," but not everyone can enjoy it. For around 10% of Americans, 10% of Africa's Tutsi tribe, 50% of Spanish and French people, and 99% of Chinese, a tall cold glass of milk means an upset stomach and other unpleasant digestive side effects. [b] In fact, most adults in the world are lactose intolerant and cannot digest lactose, the primary sugar in milk. [/b] And yet, regardless of our ancestry, most of us began our lives happily drinking milk from a bottle or breast — so what happened in the intervening time? Why do so many babies enjoy lactose and so many adults avoid it? Lactose is broken down by a protein called lactase, which acts as a pair of molecular scissors, snipping the lactose molecule in two. Anyone who drank milk as a baby carries a working version of the gene that codes for lactase. In lactose tolerant individuals, that gene keeps working into adulthood, producing the protein that digests lactose and makes eating ice cream a pleasant experience. But in people who are lactose intolerant, that lactase gene is switched off after weaning. [b]Now, new research reveals that the Stone Age ancestors of European dairy-lovers probably couldn't digest milk either. [/b] So how did they get from bellyaches to milk mustaches? The answer is an evolutionary story that takes us from the milkmaids of the Alps to the Maasai herdsmen of Africa. [b]Where's the evolution?[/b] [i]Mutations that keep the lactase gene permanently switched on are common among modern Europeans — but not among their ancestors. In March 2007, a team of German and British researchers announced that they went looking for that mutation in the 7000-year-old fossils of ancient Europeans and came up empty-handed.[/i] The researchers managed to extract the length of DNA corresponding to the lactose tolerance mutation from eight Neolithic human fossils and one Mesolithic fossil, but those DNA sequences did not carry the telltale mutation. [b]The results suggest that as late as 5000 BC most ancient Europeans could not have digested milk as adults — and that they only later evolved into milk-drinking societies.[/b] [/QUOTE] http://evolution.berkeley.edu/evolibrary/news/070401_lactose [/QB][/QUOTE]
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