Why We Keep Getting Faster

Hey! You may remember me from the posts about genetics in the universe of Game of Thrones. I’m thrilled to become a regular part of Mad Art Lab. I’m taking a short break from talking about Westeros to talk about real life; but I have a couple more Game of Thrones themed posts coming up.

So recently, one of my friends asked me this question: we keep breaking Olympic records. Is this because we’re evolving to be faster?

The idea that we’re evolving to be better athletes is a pretty comforting notion, right? That in a few generations everyone will be able to run a five minute mile and lift more than their body weight. Unfortunately, I had some bad news: it’s rather unlikely that breaking records means our gene pool as a species is getting better. It’s more likely due to technological and training improvements.

Usain Bolt: the fastest man alive
I wish I could run that fast, but I don’t want to put in the work. Are you sure you don’t have some kind of genetic patch I can use?

Let’s start with something that might have something to do with biology (notice the caveats): Why does it seem like every marathon champion in recent years comes from Kenya? Part of this is almost assuredly cultural: a country that fields world champions in a sport will funnel support back into training athletes in that sport and will get more world champions. Basically, people love winning: no shock there.

Benjamin Kiptoo in the 2011 Paris Marathon
No matter how much you train, you’ll be that tired at some point during your marathon. Who would do that without social support?

In general, though, common wisdom is that Kenyan runners have a biological advantage: they tend to train at high altitudes. At high altitudes, there is less oxygen in the air, and so your body has to change in order to keep your blood nice and healthy and red. Anyone, no matter where they were born, can climb a mountain and get used to the thin air and their body will physically change to make up for it, in some ‘good’ ways and some ‘bad’ ways. Your heart rate will speed up, your blood pressure will rise, and you get more blood flow to your brain, which basically means your body is steeped in more ‘fresh’, oxygenated blood. Your blood plasma volume decreases, and you start making more red blood cells, which means that every unit of blood has more hemoglobin and can more effectively grab oxygen from your lungs. And finally, your muscle fibers get thinner, meaning oxygen-dependent mitochondria are closer to the edge of the cell and oxygen can get to them more readily.

A sign warning of altitude sickness
Altitude sickness is the other side of this coin: if you don’t give your body time to get used to the thin air, it can be very dangerous.

Can you see how someone who had more blood, with more oxygen, and muscles that used that oxygen more efficiently, would be a better runner?

Why, then, aren’t the best runners in the world from Tibet? Tibet is, after all, higher up than Kenya. And in native Tibetan populations, we see even more physiological changes, indicating that some active evolution has made these populations particularly well suited to living at high altitudes. One hypothesis is that the average man in Nairobi is taller than the average man in Lhasa. Sadly, any demographic data pertaining to African populations is incredibly hard to come by. And what with the ongoing international argument about the independent status of Tibet, that isn’t any easier. Chinese men are on average about 5’6” tall, which is pretty close to the international average, but without any data on Kenya it’s pretty useless. But that’s at least a possibility. And it would be somewhat genetic.

Runners in the 2009 Mumbai Marathon
Longer legs will serve you better whenever you run, and that can be genetic.

But here’s another thorn to throw into the argument: nutrition. Height is genetic, in general, but it’s trumped by nutrition. A lot of things work this way: there are genes that make it easier for someone to build muscle, but if you don’t eat any protein you still won’t bulk up. And there’s one really cool factoid that brings this home. When you consider first generation immigrants and their children, if the parents were tall for the town they grew up in, the children will often be tall for the town their parents immigrated to: even if the average heights in those two towns were vastly different. Basically, as we get better at feeding more people, more people can grow to their full potential, and there will be more taller people and more faster runners.

Michael Phelps
I mean really, have you seen how much he eats?
So it seems to me that the dominance of Kenyan runners in the marathon, and the dominance of the US basketball team in the Olympics, has more to do with culture and training than genetics. But, hey, we’re not asking why certain countries are powerhouses in certain sports. We’re asking why records keep getting broken.

But as far as I can tell, those two things are very tightly inter-related. People noticed that runners who lived in the mountains did better, and started training in the mountains. And so everyone started getting faster. That has everything to do with how you train and nothing to do with genetics. Someone who gets a better running shoe or finds a better swim suit would have a leg up on his or her competitors as well, without meddling with anyone’s DNA. And don’t even start about the constant race between athletes who want to dope and authorities who want to shut down doping. But the biggest improvement we’re going to see in upcoming years (hopefully) could be nutrition-based: if more people have better nutrition, we as a species will be stronger and faster.

Darth Vader and tow schoolgirls
We have always depended on technology for our survival. And technology evolves faster than genetics.

Is it possible that people are evolving to be taller, leaner, and better at marathons? Yes, but it would be hard to see with all the confounding effects that I talked about above. You would need to ask two questions: is speed at running a marathon an inherited trait? I could believe that parts of it – things like the length of your legs, the strength of your heart, and your capacity to build the right kind of muscle – were. Do fast runners generally have more children than slow runners? That’s what I’m not so certain of.

Elizabeth Finn

Elizabeth is a geneticist working for a shady government agency and therefore obliged to inform you that all of the views presented in her posts are her own, and not official statements in any capacity. In her free time, she is an aerialist, a dancer, a clothing designer, and an author. You can find her on tumblr at, on twitter at @lysine_rich, and also on facebook or google+.

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  1. Thanks for making me think about this. I’ve never been a runner, I have asthma and now a bad ankle. My asthma always kept me from running. I have a friend who trained himself over years to run with asthma though, it took a long time to get his lungs strong enough for it.

  2. Thanks, Brian!

    Madfishmonger: I can empathize; my brother struggled with asthma and eventually found a way to work through it and swim competitively. It helped his lungs in the long run, but getting there took massive amounts of determination and dedication. In the end it’s about building up a virtuous cycle: things are fun when they’re easy, so we do them more, so we get better at them, so they’re easier. And any initial stumbling block can completely mess that up.

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