They get a selective advantage of 1.5% for the European lactose tolerance allele: “We estimated the selection coefficient on the derived allele to be 0.015 (95% confidence interval; CI=0.010-0.034) using a method that fits a hidden Markov model to the population allele frequencies as they change over time. ”
That’s way lower than any other result I’ve ever seen, including runs I’ve done myself. I’ve seen estimates a full ten times higher. I don’t get it.
West Hunter 
What did you think of that PLoS paper on the LP allele in Poland that I posted a few days ago?
Seriously, though.
I think Bell Beaker people invented crude pasteurization (within their distinctive vessels). Then they spread their genes along with their unspoilt milk products and beer (AKA clean, nutrient rich water).
People didn’t hold much truck with vampires back then.
If the advantages of drinking milk are a) calories and b) maybe something else that would mean the potential advantage would be proportional to the lack of alternative sources of calories in a particular region at a particular time so maybe there was a big advantage once upon a time in specific regions and since then only a minor advantage due to the something else.
Although at the same time unless you have a way of drinking it without getting diarrhea then you’d think the loss might outweigh any gain.
today’s wild theory…
what if certain foods reduce the symptoms of lactose intolerance enough to push the gain/loss positive if milk is eaten with those foods thereby laying the foundation for a strong selective pressure e.g. oats, fed to the horses on the steppe, fed to the people in Scotland?
“Kingsfoil, that’s a weed!”
“oats, fed to the horses on the steppe, fed to the people in Scotland”: the classical reply is that that’s why the steppe produces fine horses and Scotland fine men.
no doubt 🙂
I think there’s a missing hyperlink.
Are they giving an annual rather than a generational rate?
I checked: they’re not, as far as I can tell.
I’ve never understood why losing lactase after weaning has ended is so advantageous. Sure it’s useless – how many animals ever come in contact with milk post-weaning? – but I wouldn’t think it’s costly enough to justify eliminating. Yet everything has eliminated it. It’s odd.
I’ve always assumed it’s a way to cause weaning to happen, allowing the mother to focus on the next batch, but I’ll admit to having no justification for this assumption.
Ooh, that’s an interesting explanation. Although the effects don’t seem to be severe enough for many people to realize they’re lactose intolerant, so I’d question how effective the strategy would be.
That is an altruistic explanation.