In defense of the endurance running hypothesis, part 1: how we think about evolution.

The endurance running hypothesis is the idea that humans evolved primarily as endurance runners. The argument goes that the human physique evolved and took its shape and function from the primary adaptive pressure of persistence huntingthat of chasing down our prey until its body shuts down.

However, this hypothesis is not without its detractors. A significant amount of scientists provide an array of counterevidence to the endurance running hypothesis. (And the debate continues.)

Take for example the case of the human gluteus maximus (butt muscle). Lieberman et. al. (2006) claim that the human gluteus maximus evolved its shape and size due to endurance running.

However, another article in the Journal of Comparative Human Biology finds that the gluteus maximus grows much more in high-force sports (weightlifting) and high-impact sports (such as soccer), than it does in endurance running. In fact, they also show that the butt muscle in endurance runners is no larger than in the non-athlete population.

What I disagree with is their conclusion, which is paraphrased in the “What does this mean?” section in the image below:

“The human gluteus maximus likely did NOT evolve through endurance running, but through varied explosive and forceful activities.”

gluteus-maximus-size

My disagreements with the article (and the image) are primarily about how and why we interpret the science to mean a certain thing.

At first blush, the fact that endurance running doesn’t enlarge the gluteus maximus as much as other sports seems to detract from the idea that the muscle takes its shape from endurance running. But I think it actually adds to it.

By my analysis, these findings show that the basic, untrained shape and size of the gluteus maximus—it’s “factory specifications,” if you will—assume that it’s going to do the amounts of cutting, jumping, weightlifting, and sprinting that a habitual endurance runner might need to do. But it requires aftermarket modification to meet the (literally) outsize power and stability requirements of soccer or weightlifting.

Let’s say that a muscle evolved under a particular adaptive pressure. This means that its shape and size literally evolved to do that thing. If you take a muscle that usually doesn’t do a thing for which it evolved to do, and you ask it to do that thing, you are asking it to do something that it has prepared to do for millions of years of evolution.

In order to fit a function that it has been designed to do, the changes in shape and size that the muscle should have to undergo should be smaller, not larger. You would expect a muscle to change far more if you ask it to do something that is less aligned with its evolutionary job description.

Let’s illustrate this by looking at the arm and hand.

We probably all agree that one of the things that specifically sets us apart from our hominid cousins is the ability to coordinate the thumb with the rest of the fingers in order to grasp and manipulate objects to a high degree of dexterity. In its simplest form, this is the capability to oppose the thumb and the fingers—to make an “OK” sign with the thumb and each of the fingers of each hand.

Now let’s take a snapshot of the people who take this unique human ability to its very pinnacle: string musicians, graphic artists, etc. Their livelihood depends on the degree to which they can explore the potential of one of the major evolutionary functions of the human hand.

Compare the forearm muscles of a violinist or painter with that of a weightlifter. The weightlifter’s arms, hands, and shoulders will be much larger and more powerful. (I trust I need not cite a scientific, randomly-controlled study on the matter.) Why? Quite simple: weightlifters engage in activities that develop the body to phenomenal proportions.

But if we go by the conclusions of the article, the fact that the arm and hand get bigger through weightlifting would mean that it didn’t evolve for the kind of fine motor control that you produce in the arts. (Or that lifting heavy objects is its primary evolutionary role). A particularly ambitious version of this argument would be to suggest that one of the core functions of opposition is to become better able to lift heavy objects. But all these suppositions break down when you realize that our primate cousins were not only quite able to grasp branches and use them ably, but that opposition emerges at the same time that hominid arms were becoming smaller (and less powerful), not larger (and more powerful).

Of course, the human hand (and upper extremity in general) still needs to be able to grow and develop in order to be able to lift heavy objects—and can indeed grow to a huge degree to exhibit that function. But its core evolutionary function is to produce the unparalleled dexterity of the human being.

Furthermore, the fact that the non-painter’s hand remains relatively unchanged in size compared to the painter’s hand means that the non-painter’s hand is already relatively set up to perform that kind of dextrous function—because that’s what it presumably evolved to do. This should serve as evidence (not counterevidence) that the hand is primarily for painting (and other fine motor tasks), not for weightlifting.

We should think the same of the gluteus maximus.

Let me conclude by saying that nothing I’ve written here means that the gluteus maximus evolved exclusively for endurance running. Indeed, there is ample evidence suggesting that the architecture of the gluteus maximus is uniquely multifunction as far as muscles go. (In future posts, I’ll delve more into the nuanced view of the gluteus maximus that I proposed above: that it owes its shape and size to the fact that it is a muscle designed for the kinds of “varied explosive and forceful activities” that a bipedal, primarily endurance running animal expects to have to do.)

But what we can say is that the fact that the gluteus maximus gets bigger through a particular stimulus has no bearing on its core evolutionary role, (or on the evolutionary story of the organism as a whole).

6 thoughts on “In defense of the endurance running hypothesis, part 1: how we think about evolution.”

  1. “It is often stated that human locomotion was an adaptation to running on the open plains, which is illustrated by expressions such as ‘Savannahstan’, ‘endurance running’, ‘born to run’, ‘le singe coureur’, ‘dogged pursuit of swifter animals’ etc., even on the cover of the most influential scientific journals. Verhaegen et al. (2007) disproved in detail all endurance running arguments (Bramble & Lieberman 2004) that our Homo ancestors during most of the Pleistocene were adapted to running over open plains. When we analyse human locomotion into more elementary components, the running ‘explanation’ appears to be a just-so interpretation (cherry-picking): Bramble & Lieberman (2004) interpret every locomotor trait in humans as having evolved ‘for’ running, without even considering possible wading or swimming scenarios. A comparative approach shows that, for each trait, semi-aquatic scenarios provide more parsimonious explanations (Table 4 in Verhaegen et al. 2007), and that extant human running is a secondary and conspicuously imperfect adaptation which evolved late in the human past, for instance, we run maximally 32 km/hr over short and 20 km/hr over long distances, about half as fast as typical open plain mammals. … The nowadays popular ideas about Pleistocene human ancestors running in open plains are among the worst scientific hypotheses ever proposed. The surprising frequency and diversity of foot problems (e.g. hammertoes, hallux valgus and bunions, ingrown nails, heelspurs, athlete’s feet, corns and calluses – some of these due to wearing shoes) and the protection of our feet with shoes prove that human feet are not made in the first place for running. Moreover, humans are physiologically ill-adapted to dry open milieus: “We have a water- and sodium-wasting cooling system of abundant sweat glands, unfit for a dry environment. Our maximal urine concentration is too low for a savanna-dwelling mammal. We need more water than other primates, and have to drink more often than savanna inhabitants, yet we cannot drink large quantities at a time” (Verhaegen 1987 Nature 325:305-6). This does not imply to say that human ancestors or relatives never lived on savannas, only that if they did, it was at the wetlands and rivers there. Apparently we evolved running – only lately, and only about half as fast as equids, bovids, felids or canids, and even slower than arboreal primates – *in spite of* our broad build, short toes and plantigrade feet, profuse sweating, and large subcutaneous fat tissues (a burden of >10 kg in most people). Of course, healthy adult men can sometimes outrun ungulates (the usual ‘argument’ of conventional paleo-anthropologists) and provide a limited part of the calories for the group, but this dogged pursuit is largely confined to a few inland populations in East Africa today, is derived and probably recent (less than a few thousands of years), and it requires a rather specialized technology with water bags, weapons and poisons. Quadrupedal chimps can hunt colobus monkeys and even eat them raw, but archaic Homo with their heavy bones (POS), very broad pelves and valgus knees, shorter legs and flat feet were much too slow on land. Humans have a remarkably poor olfaction (Gilad et al. 2003) and low muscularity, which make regular scavenging, and a fortiori hunting, unlikely.” (Verhaegen 2013 Hum.Evol.28:237-266)

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    1. Seems like a counterargument for a different endurance-running hypothesis article, perhaps one that is not about the gluteus maximus specifically, but rather about the characteristics you outlined (none of which were mentioned, discussed, or alluded to in this article). I promise I’ll write about all of those individually later on.

      By the way, I’m a big fan of your work. If it’s OK, I’d like to hear your thoughts about my discussion of the gluteus maximus problem, aside from whether or not its morphology means specifically that humans were endurance runners (which is specifically NOT an argument that I make in the article).

      My take on (one small feature of) the endurance running hypothesis is this:

      The idea that humans are endurance runners does not mean that we have to go toe-to-toe with other animals on every individual feature of our physiology. For example, an animal with endurance running behavior does not necessarily have to be physiologically able to fatigue the metabolism of another animal. All they have to do is to bank on forcing the prey into heatstroke before exceeding tolerable parameters of what their “water-wasting” sweating system can waste. Such a phenomenally powerful sweating system (an absolute redundancy for a water-borne animal) may be exactly the physiological equipment needed to force a prey into heatstroke—provided that the hunter understands the limitations of their sweating system and is prepared to find water soon after the hunt ends.

      By this reading, an organism whose main hunting tactic is to jog their prey to heatstroke in the very heat of the day would not just benefit from, but rather require a ridiculously overpowered sweating system that is expensive to the point of being dangerous. In other words, while it is remarkably dangerous for a “water wasting” organism to waste water in the heat of the day, it is absolute insanity for an organism without a supercharged sweating system to run for extended periods of time in the heat of the day. Precisely because of this, jogging its prey to heatstroke in the heat of the day (rather than outright “running it down”) might be a reasonable hunting strategy for an animal with sophisticated planning capabilities and an unique ability for temporal reasoning—who also happens to be the only animal with the caliber of cooling equipment that could even begin to do the job.

      Note that similar evolutionary tradeoffs are constantly made in the animal kingdom, notably the mammalian tradeoff of armor for mobility. (Make yourself vulnerable, but in doing so allow yourself to engage with your context in ways that outclass other creatures). Having an expensive, dangerous sweating system is such a tradeoff, but it’s easy to see how sophisticated planning capabilities can turn it into an asset, rather than a liability. After all, we’re talking about homo sapiens here—meaning that the people that presumably needed to evolve a sweating system this inordinately powerful could think and plan around its disadvantages as well as (if not better than) you and me.

      By the way, I certainly don’t believe that humans only evolved for running. In several ways I discussed how a hard endurance running reading cannot be applied to the gluteus maximus (the main topic of the article). As one more example (and without taking into account the mountains of evidence) we’d be hard-pressed to argue how opposition of the thumb and forefinger evolved for endurance running. So there is no doubt in my mind that the human body is in fact a machine for which running is one function of many—or more strongly put, that the human body evolved far more for flexibility of movement generally (and, of course, flexibility of locomotion specifically) than for running in particular.

      So, I believe that a “hard” reading of Lieberman’s theory wildly overextends the impact of endurance running on human biology. But based on a multiplicity of factors I do believe that, whatever its specific evolutionary trajectory, the human body has ended up (in this present stage of its evolution) uniquely suited for temporally-bounded, very hot-weather running (with a “fuzzy” expected finish-line)—in particular relative to creatures with no such cooling capabilities, whose features are ill-suited for convective cooling, and who do not possess the human capability to cognitively unmoor from the present and plan for the future (which these genetically modern, full-fledged homo sapiens would also have possessed).

      (On a side note, I don’t find it difficult to imagine how a group of phenomenally cognitively, linguistically, socially, and technologically flexible and sophisticated desert animals with rich generational knowledge on desert living would be able to overcome “remarkably poor olfaction” to potentially become the most competent scavengers on the savannah.) The animals that we are discussing in such detached terms are for all intents and purposes real humans, with exactly our cognitive potential (and material knowledge of the desert that is as alien to us as mortgages are to them).

      By my reading, every viable human prey is reduced to sprinting away again and again in abject terror for an animal who “has their number”—in other words, who fully expects them to shut down in heatstroke before exceeding its own physiological limits (and being forced to abandon the hunt to retreat to a specific, pre-scouted water source that it deliberately stayed within range of). If “persistence hunting hypothesis” is too much to stomach, let’s say that I subscribe to the “Jason Vorhees hypothesis” of early human hunting.

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      1. Many thanks for your detailed answer. I don’t deny that some adult men in some tropical inland populations sometimes use (with the help of waterbags etc.) endurance running to hunt. But IMO this is a very derived & recent behaviour, not seen in most human populations (who need lots of water and if possible prefer to live near coasts & rivers in temperate or moderately warm climates, rather than in savannas).
        About poor olfaction. IIRC the size of our olfactory bulb is about 45 % that of chimps. If we had evolved from forest to plain (a fortiori hunting & certainly scavenging) we’d evolved a larger, not smaller olfactory bulb. The coastal dispersal model (Munro 2010) of early-Pleistocene archaic Homo (Mojokerto, probably 1.8 Ma, lay amid barnacles & shellfish) perfectly explains not only this olfactory reduction, but also tool use (for opening shellfish & coconuts & later also ungulates drowned or killed in shallow water or at the waterside) as well as brain enlargement (thanks to the rich brain-specific nutrients in littoral foods: iodine, FHA, taurine etc., see Cunnane 2005).
        About the gluteus maximus. There’s no need to suppose an endurance running past for all humans. Standing upright for frequent wading bipedally & walking is enough to explain our large gluteus maximus. A gradual evolution from a littoral (probably early-Pleistocene) to bipedally wading (late-Pleistocene IMO) to walking animal can perfectly explain this.
        The gluteus muscles attach at the iliac bones. Early Homo & australopiths had flaring ilia (+ long femoral necks & valgus knees): this is maladaptative to running, but was an adaptation for lateral movements of the femora (for climbing or swimming or whatever, but not for running forward).
        The Bramble & Lieberman ideas only confirm that some humans use endurance running (which nobody doubts), but they assume that our early-Pleistocene ancestors already did this at least very frequently, without even considering the possibility of wading bipedally or swimming with legs in the extension of the torso. Their ideas are unnecessary just-so cherry-picking without evidence: they’re illogical, confusing “post hoc” (after) with “propter hoc” (because).
        It’s no easy to get rid of the old savanna-running ideas (ape->man = quadru–>bipedal = forest->plain), but it will be inevitable if we want to see some progress in paleo-anthropology, google “unproven assumptions so-called aquatic ape hypothesis”.

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      2. Marc:

        Thanks again for your answer.

        I realize now that I have relatively little stake in the game as to whether humans evolved as distance runners (or whether endurance running was only possible afterwards due to a confluence of biological innovations becoming fully-fledged in homo sapiens).

        For the purposes of this particular post, I’m more interested in knocking down the argument that the gluteus maximus is designed in particular for powerful movements *because* it grows phenotypically beyond its base genotypic specifications.

        (And to knock down the argument form that a movement that requires phenotypic modification beyond present genotypic specifications is somehow more suited to that genotype.) In essence, I believe that the authors of the article were arguing that the fact that a muscle clearly alters its structure to adapt to a demand somehow means that it was already adapted to that demand (a contradiction in terms, in my book).

        I realize now that the title of my article was misleading, and that it cast my argument as defending the most common iterations of the endurance running hypothesis. I take full responsibility for that, and I’d like to clarify that was not my intent. The opening paragraphs of my argument were intended to “present the controversy” as it were, and the closing paragraphs to conclude that I had ostensibly debunked a counterargument rather than presented evidence in favor of the usual formulations of the ERH.

        I fully agree that the most salient structural characteristics of the GM (shape, origin, insertion, etc.) bespeak a muscle which is shaped primarily to enable bipedality in general, rather than endurance running specifically. Furthermore, it’s also clear that GM architecture is much more informed by the need to move and stabilize on the transverse plane—a requirement of bipedality—and therefore foundational to essentially *any* adult human locomotion. Any theory of the gluteus maximus (or indeed, of general human architecture) will have to grapple effectively with these facts.

        A snapshot of what I mean: I think the argument that early homo sacrificed speed for bipedality is very strong. Relative to other animals, early homo could only be a *jogger* at best. My present argument—to be revisited once I look at your sources—is that because of a confluence of other biotech breakthroughs (overpowered sweating, cognitive unmooring from the present, sophisticated language and group hunting behavior, visuospatiotemporal animal tracking capabilities, a higher sensory vantage point relative to animals of similar weight, etcetera etcetera), jogging some animals to heatstroke shutdown by the use of terror tactics became a viable hunting strategy *despite* architectural tradeoffs that made straightforwardly “running animals down” impossible.

        My goal here is to take as many parts of the human body (physiology, psyche, etc.) and synthesize them into a behavioral story that makes sense. What I also want to do is to incorporate all available anthropological and archaeological evidence—as well as the aquatic ape hypothesis—and seriously factor it into my discussion.

        In the coming months I’ll be discussing my views in longer form and more seriously. I’d be honored if you could drop by and give me your honest take on future posts. My goal here is not to promote some agenda, but to produce stuff that makes sense.

        Thanks again.

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      3. Hi Ivan, yes, Homo sacrified speed for bipedality, but not directly: AFAICS the evolution went from arboreal (monkey-like) to aquarboreal (Mio-Pliocene hominoid “apes” in swamp/coastal/gallery forests) to littoral (early-Pleistocene archaic Homo: African-Eurasian coastal dispersal) to wading (late-Pleistocene H.sapiens) to walking & running.
        Water+salt (sweat) is scarce in savannas (savanna mammals don’t sweat much or not at all), but abundant at the coasts. In fact, the most sweating animals apart from humans seem to be overheated sea-lions on land (Bartholomew).
        For how language might have evolved gradually (breath-control for shallow diving etc.), google e.g. “speech origins marc verhaegen 2016”.
        Thanks again!

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      4. Marc:

        I see it now. Haven’t had a chance to check your sources, but it’s clear to me how the kind of sweating system that humans have would have been selected for extinction in the desert (regardless of the fact that it may have some context-specific advantages in desert environments). Pending further review, it seems like I can no longer stand behind the ERH, and rather study persistence hunting as a relatively recent behavior that is possible (advantageous?) due to the application of largely pre-evolved characteristics to desert environments.

        Thank you for taking the time out of your day to talk with me.

        Sincerely,

        Ivan

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