Have you ever wondered why you want to go for a run? Why do we have that urge, even if it is hot and humid or cold and wet, and why do we feel so miserable when we cannot go out? No other sport is so addictive…
Traditionally people thought that humans were very poor runners, as we are never able to catch another animal. However, since the beginning of this century, this has changed. Scientists such as Daniel Liebermann, Dennis Bramble and David Carrier have shown that even though we are not good at sprinting, we are actually very good endurance runners. We cannot run as quickly over short distances as for example big cats, because as we run on two legs instead of four, we cannot gallop and we therefore always trot.
No animal can gallop over long distances, and endurance running is always done by trotting. Compared to other animals of our weight, we are rather good at it: recreational runners tend to trot at 3.2m/s to 4.2 m/s (11 a 15 km/h), while most animals of about 65 kg trot at approximately 2.8 m/s (10km/h).
We are also able to keep going for much longer than most animals: many of us run several kilometres a day and participate in marathons, while wolves travel on average only 14 km/day and hyenas 19 km.
Made to run
Daniel Liebermann showed that we are made for endurance running: we have long tendons, such as the Achilles tendon and iliotibial tract, and plantar arches in our feet which act like springs and save energy during running. Thanks to our butt muscles we can stabilize our bodies, and we have a special ligament at the back of our neck (the nuchal ligament) to keep our heads still. Our forearms are light and short, and therefore easy to swing.
The most important adaptation to long distance running is probably our ability to sweat all over our bodies. It allows us to get rid of excess heat in a much more effective way than by panting. Moreover, we do not have a coat, which makes it even easier to keep cool.
As all these adaptations came along when our species evolved, about 2 million years ago, we can conclude that we are made to run. However, it does not explain why we run.
Why did our forefathers have to run?
It is unlikely that our forefathers ran to escape from meat-eating animals, as they could not gallop and could therefore never be fast enough over a short distance.
David Carrier thinks that they ran to hunt: during the heat of the day, they chased their prey relentlessly until it collapsed. The prey would have galloped to get away, but as the hunters kept coming, it had to flee again even though its core temperature was still high. After several hours of pursuit, it would simply die from heat exhaustion.
Remember that humans do not have big claws or teeth to kill prey, and as our forefathers did not have good weapons it was easier if the animal died naturally.
They might also have taken advantage of kills made by other animals. Getting there quickly, before the hyenas for example, would have been very important.
Carrier thinks that the whole family hunted together, leaving the children in a safe place with one adult, just as wolves and wild dogs still do.
This technique is called persistence hunting. It is very difficult (impossible) to prove that it was indeed what our forefathers did, but the Bushmen, the Tarahumara Indians and the Aborigines occasionally still hunt this way.
Humans took up farming only about 10,000 years ago. Compared to the 2 million years of evolution as a species, this is a very short time and we still have bodies adapted to run over the savannah.
Would it be possible that we are unconsciously trying to do what we are originally made for?
Running over the savannah was dangerous. Not only could you get injured or killed, you could also spend a lot of energy without obtaining any food, and starve. Even so, it must have been the best way to obtain high quality protein, and to make sure our forefathers kept taking the risks, evolution developed runner’s high.
Runner’s high is a feeling of general well-being that takes away the pain and suffering of hard exercise. Nobody experiences it during every run, and some people never do.
Scientists believe it is mediated by several chemicals, of which the endocannabinoids are the most important ones. Endocannabinoids are substances produced by our bodies that act on our nervous system in the same way as marijuana.
To show that runner’s high is an important evolutionary tool, David Raichlen and his team measured the endocannabinoid levels in humans, dogs and ferrets after a 30’ run. Wild dogs run to capture prey, but ferrets do not as they tend to ambush it. Sure enough, the researchers noticed a rise in endocannabinoid levels in humans and in dogs but not in ferrets, and concluded that runner’s high is typical for animals that hunt by running.
Does that mean that we run in the hope to get a high?
Your body is the only equipment you have
Running is one of the rare sports we do not need any equipment for, and in a world where about everything is done with the help of a machine or a tool, this is very special indeed. It is fascinating to explore what we can do “on our own”.
It also means that we are solely responsible for all our successes (and all our disappointments).
In his book “Why we run: a story of obsession”, Robin Harvie therefore concludes that running allows him to lead a more authentic life. I am sure we can all agree with that.
What does running mean for you, and how has it changed your life?
D Bramble and D Lieberman. Endurance running and the evolution of homo. Nature. 2004; 432: 345-352.
D Carrier. The energetic paradox of human running and hominid evolution. Current Anthropology. 1984; 25(4): 483-495.
Robin Harvie. Why we run: a story of obsession. John Murray Publishers 2011.
D Raichlen, A Foster, G Gerdeman et al. Wired to run: exercise-induced endocannabinoid signalling in humans and cursorial mammals with implications for the runner’s high. J exp Biol. 2012; 215: 1331-1336.