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Reference topic 2: Standing Up

Why humans became bipedal, and what standing up costs

ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.69 sources4 graded recommendationsTopic hub: Movement

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On 29 August 1990, in the central Kalahari of Botswana, four !Xo and /Gwi hunters (the ! and / mark click consonants) from Lone Tree chose to run. It was the end of the dry season, thick dry grass made it hard to stalk silently, and several bow-and-arrow hunts had failed. The men, !Nam!kabe, his son !Nate, Kayate and Boro//xao, were confident, Louis Liebenberg recorded, that they had a better chance of running a kudu down.1

The method, as Liebenberg describes it, is to drink as much water as possible, then chase the antelope through the hottest time of the day, when maximum temperatures run about 39 to 42°C (102 to 108°F). When it pulls ahead, the hunter tracks it at a running pace, finds it resting and chases it again. In the end the animal overheats and drops from exhaustion, or simply stops, and the hunter closes in with a spear.1

Mismatch card

The system

The upright, running, sweating body: spine, knees, springy tendons and sweat glands.

What it expects

Kilometers of walking most days, some running, carrying and throwing, and warm air that sweat can cool.

What it gets

Chairs, cars and desks; nearly a third of adults worldwide below minimum activity.57

What happens in the gap

Built-in weak points meet modern ways of loading, moving and weighing: low back pain is the world's leading cause of years lived with disability, and knee osteoarthritis in the United States has doubled beyond what age and weight explain.

The handrail

Walk most days, run a little if you can, and build up gradually. (●●○)

Strength of evidence

●●○ The anatomy is well documented and walking has trial support, but the evolutionary accounts of back pain and of persistence hunting remain hypotheses.

What this topic covers

  • ·On Two Legs, Still Climbing
  • ·The Naked, Sweating Ape
  • ·Springs, Struts and a Catapult
  • ·Running Down the Kudu
  • ·The Bill for Standing Up

The practical version is in the book: Chapter 3, The Body That Walks.

The handrail

Topic 6 covers sitting, and Topic 40 the full movement program. For the upright body:

Each recommendation carries the strength of the evidence behind it. How the grades work.

  1. Walk most days, especially after back pain

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    In the WalkBack trial, 701 adults recently recovered from non-specific low back pain had six sessions with a physical therapist spread over 6 months. By the third month they had built up to walking five times a week for at least 30 minutes. Compared with no treatment, their risk of a relapse that limited activity fell (hazard ratio 0.72). The median time to relapse rose from 112 to 208 days.6364 ●●○ (one large, unmasked trial) The walkers had more leg and foot complaints, so build up gradually. Back pain after an injury, or with fever, weight loss, leg weakness, or bladder or bowel changes, needs prompt medical attention (Topic 21).

  2. Run a little, if you can

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Any running was associated with a 27% lower risk of death from any cause, with no clear extra benefit from more.65 Recreational runners were no more likely than sedentary people to have hip or knee arthritis (pooled prevalence 3.5% against 10.2%). The authors could not tell whether that link was causal or reflected other factors, such as past injury.66 ●●○ (observational) Start with walk-run intervals, and see a doctor first if you have chest pain, heart disease or uncontrolled blood pressure.

  3. Throw and carry, for play

    EmergingEvidence grade: Emerging. Early, small, animal-only, or actively contested.

    No health trials exist. ●○○ The shoulder's reliance on stored elastic energy may help explain common throwing injuries, so build volume slowly.67

  4. Respect the heat

    ProbableEvidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.

    Your body adapts to heat with repeated exposures.68 But in a laboratory study, 24 young, healthy adults doing light activity in humid heat could no longer shed heat fast enough above a wet-bulb temperature of about 30.5°C (87°F) on average. That reading folds humidity into temperature; in hot, dry air the limit was lower still.69 ●●○ Older adults, people with heart disease and people taking diuretics (water pills) face higher risk; in humid heat, slow down, drink, and stop early.

The skeptic's corner

The case against this topic, from the research itself.

How often did anyone actually run prey down? Travis Pickering and Henry Bunn argued that the tactic is rare in anthropologists' accounts of foragers and confined to very open, very hot habitats. Over 20 years and well over 100 successful Hadza bow hunts, they wrote, "we have never observed persistence hunting by the Hadza, nor have informant interviews revealed this as a strategy they practice." By their count, only two of Liebenberg's 10 hunts were spontaneous; the rest were prompted for filming, started from a vehicle and allowed water refills, and only three of those succeeded.58 Leaving out the hunts that would not have happened without the cameras, Liebenberg counted four kills in five attempts.1 Lieberman and colleagues replied that recent foragers, with bows, spear-throwers and nets, are poor stand-ins for early Homo, a trap they called "the tyranny of ethnography." Tracking, they wrote, "must be as old as hunting."59 Hundreds of historical accounts show the tactic was widespread, not that it was common.44 And the Namib hunters mostly walked;46 even !Nam!kabe told Liebenberg that a hunter could run a kudu down while walking some of the time.1 If walking suffices, persistence hunting may predate Homo's running anatomy and so explain it less well.

Was back pain built in, or loaded on? The apes and the vertebral shapes argue for a built-in cost. Yet for nearly everyone with low back pain no specific cause can be found. It occurs in rich and poor countries alike, most of all among people in physically demanding jobs, smokers and people with obesity.60 The Tsimane of Bolivia, a non-industrialized people, report current pain, most often in the back, 1.7 to 8.2 times as often as comparison groups in Asia and Australia, after allowing for age. The authors conclude that chronic low back pain is not a mismatch disease (one born of the gap between evolved bodies and modern lives) limited to post-industrial populations (Topic 21).61 Allowing for age, low back pain became about a tenth less common between 1990 and 2020;52 its global burden grew mainly because there are more, and older, people.60 The popular claim that 80% of people get back pain at some point sits near the top of published estimates, which range from 11% to 84%.62 A fair verdict: bipedalism set the weak points, and how people load, move and weigh sets how often they fail.

Terms this topic defines

Related topics

Sources cited above

  1. 1.Liebenberg, L. (2006). "Persistence hunting by modern hunter-gatherers." Current Anthropology, 47(6), 1017-1026. https://doi.org/10.1086/508695. Hunt dates, hunters, distances, durations and temperatures from the text and Table 1 (the 1998 distance was read from a vehicle odometer); the 1990 hunt's circumstances from the section on success rates; yields per day hunted from 46 days of hunting without dogs (Tables 3 and 4); the four-of-five count ("amended data") from Table 4, which omits the hunts of 12 November 1998 and 9-13 October 2001; !Nam!kabe's remark about walking from the account of the 1990 hunt. Karoha's words and the heat-stroke episode are quoted from Appendix C; translation assistance from Lefi Cooper, Jim Morris and Xamaha. Liebenberg does not date his heat-stroke episode. It is placed here on the 29 August 1990 hunt because it followed a kudu run down by !Nate, and that is the only hunt in his account that he joined on foot with !Nate as the runner (on the 1985 hunt, also on foot, !Nam!kabe ran the kudu down and Liebenberg was separated from the hunters). (!Nate was 34 at the time of the 1990 hunt; ten hunts recorded between 1985 and 2001; Karoha was 35 at the time of the November 1998 hunt, filmed for The Great Dance; his two October 2001 runs covered 33 km and 25.1 km; the longest failed hunt lasted 6 hours 38 minutes over 35.2 km; meat per day hunted was about 5 kg by running against 2.9 kg with bow and arrow)
  2. 58.Pickering, T.R., and Bunn, H.T. (2007). "The endurance running hypothesis and hunting and scavenging in savanna-woodlands." Journal of Human Evolution, 53(4), 434-438. https://doi.org/10.1016/j.jhevol.2007.01.012
  3. 59.Lieberman, D.E., Bramble, D.M., Raichlen, D.A., and Shea, J.J. (2007). "The evolution of endurance running and the tyranny of ethnography: a reply to Pickering and Bunn (2007)." Journal of Human Evolution, 53(4), 439-442. https://doi.org/10.1016/j.jhevol.2007.07.002. The phrase "tyranny of ethnography" is credited to Wobst (1978); the list of recent technologies is the authors' own ("the bow and arrow, the spear thrower, nets, and even the spear point"). (their words: "the reasonable null hypothesis should be that early Homo had the cognitive skills necessary to track")
  4. 44.Morin, E., and Winterhalder, B. (2024). "Ethnography and ethnohistory support the efficiency of hunting through endurance running in humans." Nature Human Behaviour, 8(6), 1065-1075. https://doi.org/10.1038/s41562-024-01876-x (391 accounts from 272 locations, written between 1527 and the early 1900s)
  5. 46.Hora, M., Dattatreya, R., Struška, M., Pontzer, H., et al. (2025). "Human energy expenditure and thermoregulation during persistence hunting in the Namib." Journal of Human Evolution, 209, 103773. https://doi.org/10.1016/j.jhevol.2025.103773. "The first physiological measurements" is the authors' description. (air temperatures of 36-41°C; six oryx pursuits over 3 days, covering 49.5 km on foot over ground of up to 60°C; the healthy oryx was caught after 2 hours, with running 31% of the time)
  6. 60.Hartvigsen, J., Hancock, M.J., Kongsted, A., Louw, Q., et al. (2018). "What low back pain is and why we need to pay attention." The Lancet, 391(10137), 2356-2367. https://doi.org/10.1016/S0140-6736(18)30480-X. Global years lived with disability from low back pain rose 54% between 1990 and 2015, "mainly because of population increase and ageing."
  7. 61.Stieglitz, J., Buoro, Y., Beheim, B., Trumble, B.C., et al. (2023). "Labour's pain: strenuous subsistence work, mechanical wear-and-tear and musculoskeletal pain in a non-industrialized population." Proceedings of the Royal Society B, 290(1998), 20222497. https://doi.org/10.1098/rspb.2022.2497. The ratio compares age-standardized current pain at any site (2.5-8.2 times for men, 1.7-6.5 times for women) with WHO-ILAR COPCORD samples from Iran, the Philippines, Australia, Indonesia, Bangladesh and Vietnam; Tsimane chronic pain prevalence fell within the range seen elsewhere.
  8. 52.GBD 2021 Low Back Pain Collaborators (Ferreira, M.L., de Luca, K., Haile, L.M., Steinmetz, J.D., et al.) (2023). "Global, regional, and national burden of low back pain, 1990-2020, its attributable risk factors, and projections to 2050." The Lancet Rheumatology, 5(6), e316-e329. https://doi.org/10.1016/S2665-9913(23)00098-X (projected to reach 843 million by 2050; age-standardized prevalence fell 10.4% from 1990 to 2020)
  9. 62.Walker, B.F. (2000). "The prevalence of low back pain: a systematic review of the literature from 1966 to 1998." Journal of Spinal Disorders, 13(3), 205-217. https://doi.org/10.1097/00002517-200006000-00003
  10. 63.Pocovi, N.C., Lin, C.C., French, S.D., Graham, P.L., et al. (2024). "Effectiveness and cost-effectiveness of an individualised, progressive walking and education intervention for the prevention of low back pain recurrence in Australia (WalkBack): a randomised controlled trial." The Lancet, 404(10448), 134-144. https://doi.org/10.1016/S0140-6736(24)00755-4. Lower-limb adverse events: 100 in the walking group vs 54 in controls.
  11. 64.Pocovi, N.C., Graham, P.L., Lin, C.C., French, S.D., et al. (2023). "Effectiveness and cost-effectiveness of a progressive, individualised walking and education program for prevention of low back pain recurrence in adults: statistical analysis plan for the WalkBack randomised controlled trial." Trials, 24, 197. https://doi.org/10.1186/s13063-023-07119-0. Source for the walking dose.
  12. 65.Pedisic, Z., Shrestha, N., Kovalchik, S., Stamatakis, E., et al. (2020). "Is running associated with a lower risk of all-cause, cardiovascular and cancer mortality, and is the more the better? A systematic review and meta-analysis." British Journal of Sports Medicine, 54(15), 898-905. https://doi.org/10.1136/bjsports-2018-100493
  13. 66.Alentorn-Geli, E., Samuelsson, K., Musahl, V., Green, C.L., et al. (2017). "The association of recreational and competitive running with hip and knee osteoarthritis: a systematic review and meta-analysis." Journal of Orthopaedic and Sports Physical Therapy, 47(6), 373-390. https://doi.org/10.2519/jospt.2017.7137. Odds ratio for recreational runners against controls 0.86 (95% CI 0.69-1.07); competitive runners' pooled prevalence 13.3%.
  14. 67.Roach, N.T., and Lieberman, D.E. (2014). "Upper body contributions to power generation during rapid, overhand throwing in humans." Journal of Experimental Biology, 217(12), 2139-2149. https://doi.org/10.1242/jeb.103275
  15. 68.Périard, J.D., Racinais, S., and Sawka, M.N. (2015). "Adaptations and mechanisms of human heat acclimation: applications for competitive athletes and sports." Scandinavian Journal of Medicine and Science in Sports, 25(Suppl 1), 20-38. https://doi.org/10.1111/sms.12408
  16. 69.Vecellio, D.J., Wolf, S.T., Cottle, R.M., and Kenney, W.L. (2022). "Evaluating the 35°C wet-bulb temperature adaptability threshold for young, healthy subjects (PSU HEAT Project)." Journal of Applied Physiology, 132(2), 340-345. https://doi.org/10.1152/japplphysiol.00738.2021. 24 subjects aged 18-34; mean critical wet-bulb temperature 30.55 ± 0.98°C across humid environments.
  17. 57.Strain, T., Flaxman, S., Guthold, R., Semenova, E., et al. (2024). "National, regional, and global trends in insufficient physical activity among adults from 2000 to 2022." The Lancet Global Health, 12(8), e1232-e1243. https://doi.org/10.1016/S2214-109X(24)00150-5. Insufficient activity means less than 150 minutes of moderate or 75 minutes of vigorous activity a week; age-standardized prevalence. (31.3% of adults in 2022, up from 23.4% in 2000)

This topic carries 69 notes in the research manuscript; the 17 above are those behind the material on this page. Full source register.