Few foods inspire as much passion as our lord and saviour cheese. I am, like all mentally sound individuals, passionate about cheese. My Italian background meant I was exposed early to the holy trinity of Parmigiano-Reggiano, mozzarella and ricotta, with my earliest memories being of sitting in my mother’s lap, her alternating between feeding me baby food and cubes of mozzarella [*]. A little later comes eating beef ravioli smothered in parmesan. All relationships deepen with time, and so my relationship with cheese, extending beyond the products of the Italian peninsula into French, Greek, and other variants. Naturally, I am fond of the other forms of dairy such as milk and yoghurt, but cheese is so obviously superior that it’s hardly worth mentioning them (but I did).

So I have always felt my love for cheese to be justified by my heritage and its obvious merits. But recent research has added a tragic twist to this culinary romance story. I am one of the lucky minority (35%) of homo sapiens that has the lactase persistence phenotype, that is, I am not lactose intolerant, that is, I can eat dairy with relative impunity. This means I am similar to most others of European descent, who have this genetic trait at much higher rates than other populations. As a child, everyone starts off being able to digest lactose because our bodies helpfully produce lactase, an enzyme that allows us to digest the lactose in breast milk. Yet, tragically, the majority of humans start to lose this ability going into adulthood.

This alone is almost unspeakably sad and I am inclined to start a charitable foundation to help ease their suffering. But there is more tragedy left in this story. Since the majority of people don’t have this trait, why am I so lucky? Why do Europeans have this trait? Natural selection drives most genetic change, so the answer is that it must have been selected for in Europe relatively recently, after homo sapiens emerged as a species and spread around the globe. Estimates suggest it developed somewhere between 2,000 and 20,000 years ago, which is just about the evolutionary equivalent of a bee’s whisker. Change that rapid requires tremendous selective pressure, which is a really nice evolutionary euphemism for saying tons of people must have died without passing on their genes. And this must have happened in placid old Europe.

The real puzzle is this: whilst it might make them feel ill, most lactose intolerant adults do not become violently sick and die when they drink milk or eat cheese. Yet children, by and large, digest lactose just fine, so it must have been adults that died. With such a short timespan for the change, it’s not enough that adult lactose digestion might confer some small advantage on its recipients: stronger forces are required. The current and dominant theory for what happened is fascinating and tragic.

You see, compared to more southerly climes, Europe is cool enough that milk can keep for some time during most months, meaning it’s a more viable food source without being processed into yoghurt. Still, initially most adults could not drink it without feeling ill, so most would avoid it or drink smaller quantities of it before processing it. In regular times when crops are yielding well, this works just fine. Now, contrary to our current view of Europe as the land of plenty, historically famine was pretty common. During a famine, adults become malnourished and desperate. Desperate enough that the milk that usually gives a person a little tummy ache starts to look awfully appealing compared to, well, starving (the cows are mostly fine because they can eat things that human’s can’t, like grass). That lactose intolerant person drinks fresh milk, and, in their weakened state they have a higher chance of falling ill enough to get diarrhoea, which weakens them further—and then they die.

If the famine is severe and prolonged enough, this would considerably thin out the lactose intolerant population, leaving a higher proportion able to digest lactose. If this happens repeatedly over a few centuries, we end up with the current high proportion of lactose tolerant individuals in Europe. This means, unfortunately, that a lot of people died to create the cheese-loving culture that is my heritage.

So that’s the current story. Famine drove our non-ancestors and ancestors alike to drink milk to survive, and only those who were able to survived, and they became our ancestors. This adds even more gravitas to the already near-spiritual act of cheese-eating. So if you are of European descent like me, next time you sit down in front of a dish smothered in parmesan, or put some cheddar on your sandwich, or eat a cheesy pizza, or even just have a nice glass of milk, remember all the survivors that came before you to bring you that ability. And maybe, ironically, eat a little extra cheese in honour of those that couldn’t hack it.

[*] The events of my childhood have been slightly dramatised for this post