So this seems to be barefoot running week! I interviewed Lee Saxby, the barefoot running coach on Monday, and yesterday I looked at a study that presented a theory for why runners keep getting lower extremity injuries.
Today, I’m going to look at a review article written by two paleoanthropologists, which discusses the whole idea of human endurance running, where it came from and how significant it really is in the grand scheme of human evolution.
There is something intrinsically human about distance running (photo by Julian Mason)
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So what’s the study?
The study is called Endurance running and the evolution of homo, by Lieberman and Bramble, Nature, 2004. Why do we need a review of this sort? Well, the authors sum up the importance of their review with the following key points:
- Bipedalism is a key behaviour of hominids that possibly originated soon after the divergence of the chimpanzee and human lineages
- Running is generally considered to have played no major role in human evolution by scientists
- However, humans perform remarkably well at endurance running
- Fossil evidence of a diverse array of features suggests that endurance running is a derived human capability
OK, so as a student of anatomy and kinesiology, I like to understand as much as I can about human movement. If the development of endurance running was pivotal in the development of the modern human method of locomotion and physiology, then I’m keen to understand how and why.
As a strength athlete, I may not be overjoyed by the idea that my distant ancestors spent most of their time running marathons but that’s beside the point. Knowledge is power, or so they say…
Let’s take it from the top.
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Bipedalism is a key behaviour of hominids
Thinking about what makes humans (and hominids) different from other species is a fascinating way to dig underneath the skin of human physiology. Often, understanding why certain aspects of our physiology evolved is the key to piecing together why they behave in the way that they do. In fact, some of the greatest works of human evolutionary biology have been written on this basis:
- The Naked Ape, by Desmond Morris was one of the first, if not the first, to look at humans in this way.
- The Aquatic Ape Hypothesis, by Elaine Morgan, came much later but was no less brilliant (and, like all great theories, was completely rejected by the establishment).
- Why Cooking Made Us Human, by Richard Wrangham, coined the term “small-mouthed ape” to great effect.
So starting from the premise that bipedalism needs to be investigated has a lot of merit, in my opinion. So far, so good.
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Running is considered to have played no role in human evolution
The ability of modern human beings (especially academics) to ignore obvious clues right in front of their noses (or even their noses themselves, in the case of the The Aquatic Ape Hypothesis) will never cease to amaze me (the cholesterol hypothesis, anybody?)
So our intrepid authors note that to date most research on the evolution of human locomotion has focused on walking. Why no interest in running? Well, Bramble and Lieberman infer that this lack of attention is because humans are pretty mediocre runners really. How are we mediocre?
- Elite human sprinters are slow, with a maximum speed of just 10.2m/s, whic they can maintain for less than 15s.
- Horses, dogs and antelopes can maintain maximum speeds that are twice as fast for several minutes.
- Running is more costly for humans than for most mammals, demanding roughly twice as much energy per distance travelled for a mammal of equal body mass.
- Humans are less manoeuvrable and lack many skeletal modifications that permit high speed pursuits
That’s probably all very fair and I can’t think that anybody has ever tried to argue that hominids were ever an ambush predator like the cheetah. They remind me of my old swimming coach who was fond of saying that “if you train really hard then one day, you might be just a little bit slower than the slowest fish in the sea.”
However, if those are the only reasons for ignoring running as a key feature in the development of humans, then it makes sense to take a harder look at endurance running, as none of the above points are problematic in this regard.
So let’s keep going.
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Humans perform well at endurance running
Bramble and Lieberman argue that although humans are mediocre sprinters, their endurance performance deserves some respect. In arguing this, they make the point well that no primates other than humans are capable of endurance running.
This is an intriguing point, as it means something must have happened in order to select for it. These things do not just happen on their own, it is clear. They also compare human endurance running performance with other mammals, as follows:
- Postal horses were run for generations at an average speed of 5.8m/s
- Wildebeests prefer to canter at 5.1m/s
- African hunting dogs travel an average of 10km per day
- Wolves and hyenas travel on average 14 and 19km per day
However, looking at that data doesn’t make me completely confident that Bramble and Lieberman have a water-tight case. And when they themselves note that specialist sled dog breeds, for example, can easily run more than 100km per day in arctic conditions, day after day, the comparison between humans and canines looks much less promising.
Wolves are the best persistance hunters (photo courtesy of fremlin)
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Speaking of wolves and other quadrupeds, our intrepid authors note that humans do perform poorly compared to many quadrupeds in respect of the energetic cost of running. They note that the mass-adjusted energy cost of human running is about 50% higher than a typical mammal, including other primates.
At this point, I have to say that I was expecting more. I thought that Bramble and Lieberman would present another angle of evidence to support their interest in endurance running as a key feature of human development. Unfortunately, this would appear to be it.
I think if we want to talk about humans as endurance runners and persistance hunters in a competitive environment in which wolves (or similar) would have been competing for the same resources, we have to show why we would have been as good as or better than them. I don’t think Bramble and Lieberman have quite achieved this yet. Perhaps in a future work, there will be more convincing evidence.
In conversations with Lee Saxby, I am assured that such evidence will be soon forthcoming in future papers. I guess I will have to wait and see.
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A diverse array of features suggests adaptations to endurance running
At this point, our intrepid authors turn to the fossil evidence to consider whether there is evidence to suggest adaptations to endurance running. So what are these adaptations?
Energetics – according to Bramble and Lieberman, the mechanics of running differ from the mechanics of walking. Running uses a compliant limb in which muscles and tendons in the legs sequentially store and then release energy. In contrast to apes, human legs have many long spring-like tendons connected to short muscle fascicles that can generate force economically. In addition, they note that during running, the elastic structures of the plantar arch function as a spring. Finally, they note that longer legs might have evolved to allow a greater stride length, allowing greater running economy.
I struggle to reconcile these points with the authors’ note that humans are particularly bad in comparison with other mammals (even primates) when it comes to the energy cost of running. So how can we have evolved to become more efficient at running and yet become less efficient than other less well-evolved species?
Skeletal strength - since running exposes the skeleton to much higher stresses than walking, human runners would have evolved to reduce these stresses in some way. Bramble and Lieberman note that one strategy to lower joint stress is to expand joint surfaces to spread forces over larger areas. Many studies have found that compared to other early hominids, humans have substantially larger joint surface areas relative to body mass in most joints of the lower body. Such enlarged joints are not found in the upper limbs.
Stabilization – our team note that bipedal gaits are inherently unsteady but expanded areas on the sacrum and the posterior iliac spine for the attachment of the large erector spinae muscles, and a greatly enlarged gluteus maximus are thought to aid stability in running. Indeed, they make the point well that the glutes, which are a distinctive human feature, are recruited much more in running than in walking. They also note some features of the upper body that are considered useful in running but I think they are running into difficulties here with the development of throwing and how the shoulder girdle works to that end.
Glutes are definitely a key aspect of human development but I have never seen a marathon runner with anything resembling glute muscles or spinal errectors. I would suggest that an alternative explanation of the level of development of glutes and spinal errectors seen in endurance runners is simply to hold their bodies upright and can therefore be explained more easily by the simple transition to vertical posture.
Thermoregulation and respiration - Bramble and Lieberman note that adaptations to maintain body temperature are important for long-distance walking in open, hot environments. However, running generates much more heat and so is considerably more limited by thermoregulatory capabilities than is walking.
Interestingly, I noted during my research into this article that cheetahs often have to rest for up to 30 minutes after a kill or risk heat exhaustion, such is the level of heat they produce in their sprints. Not really relevant to this article but I liked the fact, so there you are.
Bramble and Liebeman also note that humans possess many features related to heat dissipation, including sweat glands for evaporation, reduced body hair, a narrow, elongated body form, mouth breathing (permitting higher airflow rates with less resistance and muscular effort).
Of course, these points (as well as bipedalism) can be explained in a completely different way, if you read The Aquatic Ape Hypothesis. As an ex-swimmer, I have to show some tribal loyalty here!
So, I think Bramble and Lieberman draw our attention to some very interesting features of human physiology that might have developed as a result of bipedalism and possibly as an adaptation to running (or other activity) but I don’t think the weight of evidence is convincing yet.
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Why would early humans bother running?
Having got this far, Bramble and Lieberman attack what they consider is an even more difficult question. Why would early humans bother running in the first place?
Their answer to this riddle is that by endurance running, early hominids were able engage in persistance hunting. Why would they need to do this? Well, they argue that since projectile weapons were first used only 40,000 years ago and yet animals were being eaten (using tools) 2.6m years ago, this implies that peristence hunting must have been used in the interim.
Why persistence hunting? Well, their arguments are not spelled out in this article but, in The evolution of marathon running: Capabilities in humans, Lieberman and Bramble, Sports Medicine, 2007, they note that “to be a camivore, one must compete with other camivores, yet these hominids were not only comparatively slow, but also lacked any weaponry more sophisticated and dangerous than simple stone tools and possibly sharpened, untipped spears.”
Why is this a problem?
Well, according to Bramble and Lieberman, “because one kick from a moderate-sized animal can be lethal, modem human hunters do not hunt with spears without first trapping or disabling an animal, using technologies not available for most of hominid evolutionary history.”
In other words, we must have used persistence hunting because ambush hunting large, herbivorous animals with simply spears would have been too dangerous. So it couldn’t possibly be entertained by modern man (hat tip to Jamie at Chaos & Pain (NSFW) for the awesome movie reference).
One man, a spear and a really huge set of cojones
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Wrapping up
So we started this review with a couple of key points to investigate:
- Bipedalism is a key derived behaviour of hominids that possibly originated soon after the divergence of the chimpanzee and human lineages
- Running is considered to have played no major role in human evolution
- But humans perform remarkably well at endurance running
- Fossil evidence of a diverse array of features suggests that endurance running is a derived human capability
Along the way, I agreed that bipedalism is worth investigating and that running should be looked at to see whether it has influenced the human physiology. However, I was not convinced by the arguments put forward to suggest that humans perform well at endurance running nor the arguments suggesting that humans have developed features specific to endurance running.
At the end of the day, I cannot get past the idea that we suck as persistence hunters when compared to wolves. I would guess it was more likely spears and a really big pair of cojones that won the day. Sadly, I suspect that many people will not be able to bring themselves to accept that human beings could do such things.
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So if none of the above has put you off barefoot running (which it should not do!), then don’t forget that it’s better to learn how to run barefoot properly rather than just jump in with both feet, as we found out in my interview with barefoot running coach Lee Saxby yesterday. You can find more information about Lee and his clinics here. And if you are in the UK in mid-December, you can catch one of Lee’s workshops in London. See the details in the flyer below:
