Travel Made Humans

I hadn’t till now appreciated how central long distance travel was to early human evolution. A 2004 Nature article:

No primates other than humans are capable of endurance running. … Well-conditioned human runners … can occasionally outrun horses over the extremely long distances that constrain these animals to optimal galloping speeds, typically a canter. … Horses have … narrow ranges of preferred speeds for trotting and galloping and gait transitions that minimize cost. … Human runners differ from horses in employing a single gait. … Humans are thus able to adjust running speed continuously without change of gait or metabolic penalty over a wide range of speeds. …

Considering all the evidence together, it is reasonable to hypothesize that Homo evolved to travel long distances by both walking and running… Endurance running is not common among modern hunter-gatherers, who employ many technologies to hunt (for example, bows and arrows, nets and spearthrowers), thereby minimizing the need to run long distances. But Carrier has hypothesized that endurance running evolved in early hominids for predator pursuit before these inventions in the Upper Palaeolithic (about 40kya). Endurance running may have helped hunters get close enough to throw projectiles, or perhaps even to run some mammals to exhaustion in the heat. …

Another hypothesis to explore is … in the open, semi-arid environments … early Homo may … have needed to run long distances to compete with other scavengers, including other hominids. … Similar strategies of ‘pirating’ meat from carnivores are sometimes practised by the Hadza in East Africa. … It is known that major increases in encephalization occurred only after the appearance of early Homo. … Endurance running may have made possible a diet rich in fats and proteins thought to account for the unique human combination of large bodies, small guts, big brains and small teeth.

A 2009 Evolutionary Anthropology article on “The Emergence of Human Uniqueness”

Important preadaptations in the genus Homo … led to human uniqueness. First, hominins are bipedal and, as a result, cover geographical ranges far larger than other apes do. Even hunter-gatherers living in tropical forests have daily home ranges that are two to three times those of chimpanzees, and lifetime home ranges more than two orders of magnitude greater. Thus, individual hominins faced more environmental variability than do chimpanzees. … This would favor social learning capacity.

Second, bipedal hominins evolved exceptional manual dexterity because their hands were freed from locomotory constraints, and they could carry tools with little cost. This would have favored increased tool using and making behavior and probably increased selection pressure on imitative capacities as well. Third, by at least 2 million years ago, hominins had begun to depend on high-quality, widely dispersed resources that were difficult to obtain. This shift of feeding niche had important life-history implications. Juveniles could not fully feed themselves due to the complexity of the extractive niche, and this led to their provisioning by close kin. As large package foods became common, the foods returned to the juvenile home base were probably ‘‘shared’’ by coresidents. This …. might partially explain why hunter-gatherers experience early adult mortality at one-fifth the rate of wild chimpanzees. That pattern would favor a life history with later age at maturity and delayed onset of senescence. …

Here we present a possible chronological sequence of related adaptations that form a set of working hypotheses for future research:
A. Bipedality led to manipulative dexterity, low-cost transport, and larger home range. These traits favored more extensive tool use and greater selection for social learning capacities. The transition to larger social groupings is clearly evident by [~60-24kya], including a shift toward central place foraging and increasingly distant resource forays among all hominins of western Eurasia at least. Oldowan tools indicate abilities not present in other apes. Amplified home range was a critical preadaptation for the subsequent dietary shift to widely dispersed but nutrient- dense resources.
B. Dietary shift to a hunted and extracted diet created juvenile dependence on adult provisioning. This promoted kin-based cooperative breeding along with evolution of early prosocial emotions, enhanced theory of mind, shared intentionality, and more complex communication that facilitated task specialization and integration of the shared goals of cooperative breeders. The emergence of a home-base economic system allowed adults debilitated by ill- ness and injury to recover, favoring later senescence and later sexual maturity.
C. Imitative capacity and shared intentionality interacted to produce cumulative cultural capacity. This relied on a pedagogical mode of interaction in which imitators presumed that models were motivated to help rather than compete with them. …
D. Cumulative cultural capacity and prosocial emotions led to language, social norms, ethnicity, and extensive nonkin cooperation. This allowed the emergence of social norms regulating mate exchange between kin groups and promoted intergroup peaceful interaction due to cross-cutting genetic interests, as well as the emergence of gifting and trading. Because of the increase in effective interacting group size … cultural accumulation sped up enormously.

Finally, an interesting 1999 theory:

Extensive nonkin cooperation [led] to all major elements of human uniqueness. Coalitional enforcement arose uniquely in humans when the animals that founded the Homo clade acquired the ability to kill or injure conspecifics from a substantial distance. This resulted from the evolution of hominid virtuosity at accurate, high-momentum throwing and clubbing, previously supposed to be adaptations for hunting, predator defense or individual aggression. No previous animal could reliably kill or injure conspecifics remotely. This ability dramatically reduced the individual cost of punishing noncooperative behavior by allowing these costs to be distributed among multiple cooperator.

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  • Richard Wrangham’s “Catching Fire” argues that eating meat (and preparing it before eating) led to larger brains since we didn’t need to devote as much energy to digestion. He also thinks that cooking led to the marital pair.

  • I have trouble going along with the coalitional enforcement theory as presented in the abstract. (The article is gated.) The connection between throwing and enforcing norms is troublesome. I can’t think of any examples where group norms are enforced by killing at a distance. When a group of humans wants to visibly enforce a rule, they capture the offender, and punish is administered at close range. The only killing-at-a-distance that is normal for humans is either surreptitious or in wartime.

    The rest of your post is a nice packaging of the various aspects of our evolutionary background. I’ve just finished Ridley’s Rational Optimist , and the main thing he adds to the story is the importance of trade among strangers. This seems to reinforce the right kinds of sociality, and to have an appropriate comparative timeline with the rest of the story.

    • Buck Farmer

      Stoning? Not at all familiar with it, but this seems like the more recent analog of the group punishing defectors from a distance.

      It seems though that you could also punish defectors with exile i.e. exclusion from interactions and group resources, but perhaps this is easier when they can’t get close to you?

    • anon

      My guess is that the ability to injure cospecifics easily would lead to a breakdown in chimp-like dominance hierarchies. Coalitional enforcement and social politics would co-evolve, in order to (1) strategically manage the new-found ability and (2) provide leading individuals with some kind of ‘legitimacy’ or political cover, such as by making troop leadership largely egalitarian, or dependent on the “leader” providing resources or services to the troop.

    • Zach K

      Why are you separating wartime from rule enforcement? Most wars seem to be started by owners of distance weapons to get other people to follow their rules. It’s only falling cost of technology that lets distance weapons to be owned and easily operated by a majority of people.

  • Thanks, TGGP. Ridley also brings up the importance of cooking in enabling a smaller gut, and it also reinforces the home-base part of the story.

  • DK

    All this is alone the same line of (faulty) logic as Marx & Engels’ suggestion that it was toolmaking that “made humans”.

  • This BBC documentary has more on persistence hunting

  • Individual Hominin

    individual hominins faced more environmental variability than do chimpanzees. … This would favor social learning capacity.

    “The Dymaxion Map shows that (1) the colder an area gets, the more the annual temperature variation, and (2) the more the geographical temperature varies annually, the more inventive the humans who live in those areas have to be to survive. If you live by Lake Victoria in eastern Africa and you
    wish to cross it, you will invent a wooden boat. If you live beside Lake Baikai in central Siberia and you wish to cross that body of water, you will invent a wooden boat in the summer and skates and sleds in the winter. The people who live in the colder areas are not more inventive – they simply have many more environment-caused occasions in which to employ all humans’ innate inventiveness. Move humans from a hot country into a cold country, and they become as inventive as those who live there – or they perish.”
    – R. Buckminster Fuller, Critical Path 1982

  • IVV

    There’s a bit of a chicken-and-egg problem with food preparation I’ve been curious about.

    We need a brain of a particular size to discover fire/food prep. We need enough gut freed up in order to have the metabolic needs for bigger brains. We need to have better food in order to survive with a smaller gut. We need to discover food prep to get better food.

    But let’s say we become bipedal first. So, in the early days, we don’t use food prep for better food, we use a wider range to procure better food (more nuts, more game). We’ve got free hands, but perhaps we’ve got cruder tools to use with them. Those of us with bigger brains both coordinate better and make better tools, giving us more reason to have more dexterous hands.

    What makes bipedality so useful? Our hands are free to carry our tools around. We no longer have to hope that the game comes to where our tools are, we can carry our tools to the game. Since all other animals need to bring the tool to the prey, we’ve become much better at it, and tools becomes a viable long-term strategy for the species.

    Greater range allows for greater nomadicism. So now we’ve got a species that’s better at carrying and using tools, and going from place to place in accordance with the seasons. So now, any minor advantage in those fields–better hands, better running, better brains, better food prep, better group coordination, greater lexical understanding of the animals and plants in any particular location at any particular time… will be a boon to the species. So now, the smarter, more social throwers become dominant.

    Wow, a lot to think about.

    • Dave

      Damn,just like Little League baseball!

  • I suspect that being able to walk easily has been more important than running.

    I didn’t know that cursorial hunting was rare, but I’m not surprised. Waiting for an animal to show up and then throwing spears at it sounds a lot easier than spending days running it down.

    The Hand: How Its Use Shapes the Brain, Language, and Human Culture has somewhat about the evolution of hands, and (at least when the book was written) whether improved hands drove intelligence or the other way around was a disputed topic.

    Is there evidence from fossil bones about what sorts of activities paleolithic people did the most?

    • Douglas Knight

      You should probably read the first article, or at least its last section.

      The quote only says that endurance hunting is rare among modern hunter-gatherers. The context is skeptical of ancient practice, but there is no direct evidence either way.

      The point of the article is that there are adaptations for running. It was selected for and is not just a byproduct of walking. That is compatible with walking being more important, though.

      • Ron Bales

        You make a very good point in emphasizing the potential difference between modern hunter gatherers and those of the past. We know that there are differences. If only that modern hunter gatherers are still hunter gatherers.

        The species is clearly selected and adapted for long distance running. We are far too good at it to assume it was the result of an accident.

        Another aspect that deserves thought and research is the long-term cooperative relationship with the other great long distance runner, dogs. The two best long hunters on the planet have been working together since time immemorial with adaptations for this relationship visible on both sides. To the extent that dogs and humans can read one another’s gestures even if they’ve never met.

    • That paper that found humans’ shorter toe length gives a huge efficiency gain in running, but none in walking, suggests that running has been an important focus of adaptation.

      Also, it’s not a study or anything, but the television show Nova did a stunt a few years ago where they had ten months to train a bunch of sedentary people (many of them obese) to run a marathon, and almost all of the subjects were able to complete the marathon! It’s kind of amazing that almost any human can run a marathon.

  • Zach K

    glad to see you linking to Bingham’s paper on the throwing theory. His new book on the subject is here:

  • nyc561

    FYI – I believe this article was used as a primary source for the bestselling non-fiction book on the Tarahumara indigenous tribe of Northern Mexico, BORN TO RUN. Great read for anyone interested –

  • In Language in Hand: Why Sign Came Before Speech by William C. Stokoe [google books], Dr. Stokoe argues… well, that gesture came before vocalization. Haven’t read it yet.

    I can imagine that standing upright frees your front paws up to do other things. Having one noun (“you”) and one verb (“there”) expressed in gesture can lead to some pretty complex planning. You (me), you (that guy), you (that guy), there (where we all see the food). You (that other guy), there (watch our stuff). The lines between body language and gesture, and gesture and sign language, and sign language and vocal language, can get pretty thin.

    My bias: I’m a sign language interpreter.

    • Buck Farmer

      Definitely true. Living in a country with few English-speakers and less than fluent grasp of the local language, I am daily astounded by how naturally and universally people learn to communicate with gestures.

      Usually it relies on common-knowledge that “speaker” and “audience” can see all relevant pieces of the situation and have known motivations.

      With how strong and versatile gesture / body language is, what would have pressured the creation of spoken language? It seems spoken language is most useful for refering to people / objects not present (though this can be done in sign language too, but is more sophisticated than the naive gestural language I encounter).

      What would precipitate the need to talk about non-present others? The benefits are obvious, but presumably many animals get on fine without this ability. What changed?

      • John Laing

        Wolves howl to communicate beyond line-of-sight, which is useful when coordinating a search party across a wide area of uneven terrain; back-of-the-envelope calculations suggest it doubles the area a given group can search in a given time, just by reducing redundancy and the need for relays. It’s possible early humans picked up howling just like wolves picked up hand gestures.

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  • Bram

    Maybe no coincidence that our first domsticated animal – wolves / wild dogs – are also persistence hunters.

    Sure ambush hunting is less effort, if it works. Ambush hunting large animals is also more dangerous and has a higher probability of failure.

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