The Lactose Tolerance Mutation

Recently, Boyfriend learned how to make yogurt at home. It’s not a big deal, of course – my mother’s been making yogurt at home ever since I can remember. But given the temperature and humidity where we live (and the fact that Boyfriend is inherently incapable of following instructions, and usually prefers the “wing-it” method), it’s taken him a few attempts to perfect the art of yogurt-making. And now that he has, the contents of our fridge make me feel like we live on a dairy farm. Here’s a brief sample: whole milk, vitamin D milk, 2% reduced fat milk (apparently there are textural variations in the yogurt made from each of these), a big pot of fresh yogurt (made yesterday), a smaller pot of not-so-fresh yogurt (made five days ago and being preserved for its cultures), strained yogurt, yogurt with cream, and yogurt without cream.

As you can imagine, this is driving me ever so slightly crazy.

“We could have a dairy party,” I suggested in my desperation to make some space in the fridge for other things – you know, like vegetables, fruit, and maybe even some food (radical idea, I know). We could make something from all that milk, such as flan or firni, and then invite our friends over to eat it.

Or we could listen for baby-wailing in the hallways of our building, and once we’ve determined which apartments contain those milk-guzzling, havoc-wreaking, illogical little tyrants, we could knock on the door with a big smile and offer a jar of the several varieties of milk we have in the fridge.

Or we could hang some raw fish out in the window so all the neighborhood cats would gather by our apartment, and we can ambush them. You thought you came for fish,didn’t you, you greedy, gluttonous, four-legged balls of cuteness? Ha! Here, have some milk instead!

Or we could find the closest marathon, pack all the milk in little sippy pouches, and toss them to thirsty, tired, and very grateful runners.

“No, that last one is a bad idea…” Boyfriend said gravely.

Yeah, because all my other suggestions are spilling over with brilliance, right?!


“An overwhelming majority of people are lactose intolerant.”

An overwhelming majority? Really? Ok, I swear I didn’t say this out loud, but clearly something changed on my face, because Boyfriend followed it up with this:

“Did you know that humans developed lactose tolerance because of a single genetic mutation that happened about 11,000 years ago?”

Ok, so first let’s get some definitions and descriptions out of the way. (And some token scatological humor too.) Here’s a clip from TV’s Big Bang Theory that nicely explains what lactose intolerance is:

Defined as the inability to break down lactose – the sugar found in milk and a lot of milk-products – lactose intolerance has serious or life threatening effects only in the rarest of cases, but is generally pretty uncomfortable. And here’s the thing – while all human beings are born lactose tolerant, by the age of about five our bodies are supposed to stop producing lactase, the gene that gives us the ability to digest lactose. The default state of all humans beyond their toddler years is lactose intolerance.


Because Nature made it so. Because it wanted to make sure that toddlers – who were entirely dependent on breast milk for survival – would be weaned off at the right time.

Nature is totally not ok with this. (Arguably, it's Game of Thrones. There's a LOT that's not ok.)

Nature is SO not ok with this. (However, it’s Game of Thrones. There’s a LOT that’s not ok.)

This system worked just fine when humans were mainly hunter-gatherers, because after children were weaned off breast milk, they got their protein and calories from all the meat they ate right into adulthood. The problem started when those clever little twits went and started farming. (Seriously, what’s up with that, Homo sapiens sapiens?) They settled down in one place, stopped hunting as much as they used to, and though life seemed better overall, nutrition was now a huge problem. They had livestock, but unlike boars or deer in the forest, these animals had many uses, so farming communities couldn’t afford to just kill all of them for food. And while they learned to milk them, they couldn’t drink the milk because they couldn’t digest it.

One of the ways in which early humans got around this was by making a lot of cheese. Archeologists have found perforated pots and trays dating back about 10,000 years with traces of dairy on them, suggesting these were used for straining cheese. Early humans were able to consume cheese because the lactose content in it is greatly reduced. However the process of fermentation also knocked away between 20%-50% of the calories found in milk, therefore making cheese lower on energy. This was a crucial factor, given the less-than-ideal living conditions of the time. In colder climates especially, calories and energy were the key to survival.

So somewhere around that time Evolution – which is usually frustratingly slow on the uptake – decided to punch a genetic mutation into a handful of human beings in Northern Europe/Central Asia/somewhere in between (obviously it has been difficult for scientists to pinpoint the exact geographic location where this mutation first appeared). It gave them what is known as “lactase persistence,” or the “LP allele”: the continued production of lactase beyond childhood, which allowed adults to digest milk. Viva Evolución!

Obviously, this was a big deal. The few adults who could now drink milk were getting more nutrition than the others, had more energy, were stronger, and had something to live on through cold, dark winters when snow ravaged the Earth and nothing grew on it. More importantly, they lived longer, and had a greater chance of getting to reproductive age and producing multiple, similarly fertile and healthy offspring. This was a major evolutionary advantage, as you can imagine: populations with this genetic mutation soon wiped out the others, and spread all over Europe, Central Asia, the Middle East, North Africa, and some parts of sub-Saharan Africa (although the mutation is said to have happened there much later). Today, most people who trace their ancestry to these early milk-drinkers probably have at least some degree of lactose tolerance.

The trouble, of course, is that this event occurred about 10,000 years ago, and most people today are of very, very mixed heritage. So one can only say with certainty that about a third of the world’s population has some degree of lactose tolerance. The rest of them are, well, you’ve watched the video above. (It’s ok, though. At least you’re not a mutant. You’re the way nature originally intended you to be – a carnivorous, nomadic, rumble-tummied hunter. Own it!)

Yeah, easy for you to say, you lactase-producing mutant of Northern European descent... (Wait - remind me again, does Wolverine get pissed off when someone calls him a mutant?)

Yeah, easy for you to say, you lactase-producing mutant of Northern European descent…

Want to know more? Go here. And here.


One thought on “The Lactose Tolerance Mutation

  1. Pingback: Neanderthals and the Addiction to Nicotine | Stuff My Boyfriend Tells Me


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