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.