Most people typically view Homo sapiens as physically rather weak; reliant upon our technology for survival in the harsh world. Picturing people without technology on the Savannah typically ends up with them becoming lion food in short order.
We’re slower than Cheetahs, less agile than a gazelle, lack the point teeth of a lion and can’t climb half as well as a chimp. Surely technology is our saving grace, the only thing we really have going for us?
Surprisingly, no. Contrary to the classic conceptualisation of people as totally reliant upon technology, we do have some surprising physical adaptations to Savannah life. In particular, we sweat.
Sweating allows us to engage in endurance running. Now, again, running might not seem to be something people are particularly good at – there are a whole host of other animals that can easily outpace us – but they can’t out sweat us.
Combine running with sweat and you have a bipedal ape with the ability to run long distances in the blistering heat, which is something most animals can’t do. Steadily a running man would tire out his prey as he chased it across the Savannah until it collapsed of hyperthermia and he was able to claim his prize.
Endurance running is the ace up our sweaty sleeve and allowed us to become one of the dominant predators on the Savannah in a war of attrition. Which of course begs the question, when and how did this ability evolve?
The ability of our ancestors to manage heat (or thermoregulate, if you want to sound sophisticated) has long been an avenue of research in EvoAnth since it ties into that other interesting question – when did we loose our fur? Unfortunately, that means that running and thermoregulation has been an area that was somewhat neglected since people care more about where all our fur went.
This means that all the mathematical models used to calculate the heat management abilities of hominins are based around someone who is standing still which isn’t particularly pertinent to those studying running. So some researchers decided to sort out this oversight and adapted an existing model to be applicable to a running man.
The result is pages and pages of rather complicated maths which I in no meaningful way understand. However, I do know that when they inputed the data for modern Homo sapiens the predictions the model made were accurate when compared to actual, non-imaginary Homo sapiens. So it is seems to be the mathematics is fairly sound, even if I am in no way qualified to comment on it.
Satisfied the model works, they then ran the calculations for to work out the thermoregulatory abilities of other species of hominin in an effort to see when endurance running became physically possible. Unfortunately, they didn’t have all the data needed to make the model as accurate as possible.
Assumptions had to be made regarding the sweating ability of the past species, as well as how much fur they had and how efficiently they could run. If they used the data from modern humans to fill in these blanks then surprisingly, they found that pretty much every species of hominin could endurance run.
However, for some species these assumptions are particularly weak. Australopithecines weren’t as good at bipedal locomotion as later species, suggesting they couldn’t run as efficiently as modern humans meaning this figure isn’t accurate for them and they would likely be unable to engage in long distance running.
Then there’s the evolution of the human louse, which indicates that hair loss only got to human or near human levels during the time of Homo erectus, eliminating Homo habilisand other earlier members of our genus from those capable of long distance running.
So what about sweating? Was Homo erectus a good enough sweater? Well the maths reveals that provided they could sweat at >80% of the efficiency as modern humans then they could engage in endurance running. Since they had a body that is physically rather similar to modern people this does not seem like much of a stretch.
So, it would seem that Homo erectus was the first hominin that could’ve engaged in long distance running – except for during midday – although that doesn’t mean they actually did. Which leads to the follow-up question of how did they evolve this ability?
Well, given that endurance running requires that they can simply run, sweat and not have much fur (all of which could develop for other reasons) then it might well be that long-distance running is simply a side-effect of other selection pressures.Our ancestors got good at running to sprint and escape from predators/chase prey/whatever and were able to sweat well because the climate was so hot and bingo, they’d accidentally developed the ability to run for long periods of time.
Of course, there might have been other factors involved and I await any further research that tries to shed light on exactly why endurance running emerged. Also, as the field of recreating the bipedal abilities of past hominins expands, the data regarding the running efficiency of these species will improve and so more accurate results can be obtained.
However, given how Homo erectus is already known to be rather human in terms of physiology, I doubt more accurate results will drastically alter the findings of this paper.
|Ruxton GD, & Wilkinson DM (2011). Thermoregulation and endurance running in extinct hominins: Wheeler’s models revisited. Journal of human evolution, 61 (2), 169-75 PMID: 21489604|