For thousands and thousands of years, adults couldn't digest dairy products without an upset stomach and a trip to the bathroom. And then one day, poof! A few changes in our DNA gave about a third of the world's population – mostly Europeans — the ability to knock back cheese, pizza and chocolate ice cream without a care in the world. But why? Why did this ability to digest lactose suddenly crop up in our European ancestors about 10,000 years ago? That's been a big mystery for scientists… To start filling in those blanks, Sverrisdóttir and her team analyzed the DNA of bones from 5,000-year-old farmers found in northern Spain. None of the eight individuals had the genetic mutation giving them the ability to digest milk as adults. In contrast, a third of the population in Spain today is lactose tolerant. So in the span of just a few thousand years, that ability spread rapidly throughout the country. http://www.npr.org/blogs/thesalt/2014/01/23/265224739/a-milk-mystery-did-gloomy-weather-make-us-love-the-stuff

I don't see any "mystery" here. The answer is selection pressure. Once humans domesticated cattle, goats, sheep, and horses, and began ingesting their milk, lactase persistence had a selective advantage. Even the slightest selective advantage will soon produce a shift in the genetic frequencies of an entire population. The ability to digest lactose was not one that "suddenly cropped up." All mammalian neonates can digest milk, but they lose that ability as they mature, usually just after weaning. As soon as there was a milk supply available to adult humans, selection pressure began to favor lactase persistence in adults. Lactase persistence is a phenotype with more than one genotype, that is, there's more than just one allele that will produce lactase persistence, making it a convergent trait in humans. The genetic mutations allowing lactase persistence have probably arisen repeatedly in human evolution, but were not "fixed" in the population because it gave no selective advantage to the bearer of the trait. By the way, even people who are lactose intolerant (e.g., moi) can get away with eating yoghurt (including frozen yoghurt), cheese, and butter if prepared a certain way, so lactase persistence is not necessary to benefit from living in a culture including dairy husbandry. What I cannot do is drink a glass of milk or eat Ben & Jerry's (waaaa). Where lactose intolerance is a real PITA is that "milk solids" and other milk products are ingredients in many prepared foods. I have to read package labeling carefully to avoid them. Diana P.S. Most adult cats are lactose intolerant, so please do not feed your cat milk. > -----Original Message----- > From: [email protected] [mailto:y-dna-haplogroup-i- > [email protected]] On Behalf Of Matthew Simonds > Sent: Thursday, January 30, 2014 2:32 PM > To: [email protected] > Subject: Re: [yDNAhgI] Another Ancient DNA Study: A Milk Mystery... > > > For > thousands and thousands of years, adults couldn't digest dairy products > without > an upset stomach and a trip to the bathroom. > > And then one day, poof! > > > > A few changes in our DNA gave about a third of the > world's population – mostly Europeans — the ability to knock back cheese, > pizza > and chocolate ice cream without a care in the world. > > > > But why? Why did this ability to digest lactose > suddenly crop up in our European ancestors about 10,000 years ago? That's been > a big mystery for scientists… > > > > To > start filling in those blanks, Sverrisdóttir and her team analyzed the DNA of > bones from 5,000-year-old farmers found in northern Spain. None of the eight > individuals had the genetic mutation giving them the ability to digest milk as > adults. > > > > In contrast, a third of the population in Spain today > is lactose tolerant. So in the span of just a few thousand years, that ability > spread rapidly throughout the country. > > > > > > http://www.npr.org/blogs/thesalt/2014/01/23/265224739/a-milk-mystery-did- > gloomy-weather-make-us-love-the-stuff > > ------------------------------- > To unsubscribe from the list, please send an email to Y-DNA-HAPLOGROUP-I- > [email protected] with the word 'unsubscribe' without the quotes in the > subject and the body of the message