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Episode 7.4 · 14 min

Why Humans Sweat So Much

How did Homo erectus become so well suited to moving through Africa’s heat? Following evidence from the Turkana Boy, fossil bones and ancient footprints, this episode traces the rise of a taller, long-legged body built for efficient walking and better running, then asks how sweating, fine short hair and dark skin may have helped it lose heat while the costs and uncertainties remain.

Watch this film on YouTube ↗

Visual credits

21 sources

Sources and credits for imagery used in this film, including material incorporated into explanatory animations.

  • Turkana Boy skeleton cast, Natural History Museum, London

    Emőke Dénes

    View original source ↗Source licence: CC BY-SA 4.0

    Converted to PNG and resized. In the comparison animations, the skeleton was cut out, scaled and given animated limb highlights.

  • Fossil skull KNM ER 3733

    Suyash Dwivedi

    View original source ↗Source licence: CC BY-SA 4.0

    Converted to PNG and resized for display.

  • Lucy skeleton cast on a black background

    120

    View original source ↗Source licence: CC BY 2.5

    Converted to PNG; background removed; resized and given animated limb highlights in the comparison animations.

  • Running performance in Australopithecus afarensis — comparison figure

    Karl T. Bates, Sian McCormack, Evie Donald, Samuel Coatham, Charlotte A. Brassey, James Charles, Thomas O’Mahoney, Pasha A. van Bijlert and William I. Sellers

    View original source ↗Source licence: CC BY 4.0

    Figure extracted from PDF page 5, cropped and resized for display.

    © 2024 The Authors. Published by Elsevier Inc.

  • Southern Shore of Lake Turkana, Kenya

    Predatorywasp

    View original source ↗Source licence: CC0

    Converted to PNG and resized for display.

  • Sibiloi National Park

    Joshua Stevens / NASA Earth Observatory; Landsat data from the U.S. Geological Survey

    View original source ↗Source licence: Public domain

    Converted to PNG and resized for display.

    NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey. Story by Kasha Patel.

  • Running performance in Australopithecus afarensis — digital models

    Karl T. Bates, Sian McCormack, Evie Donald, Samuel Coatham, Charlotte A. Brassey, James Charles, Thomas O’Mahoney, Pasha A. van Bijlert and William I. Sellers

    View original source ↗Source licence: CC BY 4.0

    Figure extracted from PDF page 4, cropped and resized for display.

    © 2024 The Authors. Published by Elsevier Inc.

  • Turkana Boy and modern juvenile rib cages — Extended Data Figure 3a

    Markus Bastir, Daniel García-Martínez, Nicole Torres-Tamayo, Carlos A. Palancar, Benoît Beyer, Alon Barash, Chiara Villa, Juan Alberto Sanchis-Gimeno, Alberto Riesco-López, Shahed Nalla, Isabel Torres-Sánchez, Francisco García-Río, Ella Been, Asier Gómez-Olivencia, Martin Haeusler, Scott A. Williams and Fred Spoor

    View original source ↗

    Panel a extracted, cropped, padded and resized for display; explanatory colour label added by the renderer.

    © The Author(s), under exclusive licence to Springer Nature Limited 2020.

  • FE22 TS-2 footprint surface map — Figure 2A

    Kevin G. Hatala, Neil T. Roach, Anna K. Behrensmeyer, Peter L. Falkingham, Stephen M. Gatesy, Erin Marie Williams-Hatala, Craig S. Feibel, Ibrae Dalacha, Martin Kirinya, Ezekiel Linga, Richard Loki, Apolo Alkoro Longaye, Malmalo Longaye, Emmanuel Lonyericho, Iyole Loyapan, Nyiber Nakudo, Cyprian Nyete and Louise N. Leakey

    View original source ↗

    Panel A extracted and resized for display.

    Copyright © 2024 the authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original US government works.

  • GaJi10 fossil footprint H9 — Figure 4B

    Kevin G. Hatala, Neil T. Roach, John W. K. Harris, Purity Kiura, Emmanuel K. Ndiema, Ben Sila, David Kipkebut, Joyce Waweru, Philiphine Kisale, Apolo Alkoro Longaye, Hilary Sale and Anna K. Behrensmeyer

    View original source ↗Source licence: CC BY-NC-ND 4.0

    Panel B extracted with its scale and white margin; panel content unaltered; resized for display.

    Copyright © 2026 the Author(s). Published by PNAS.

  • Turkana Boy cast at the American Museum of Natural History

    Mike Peel (www.mikepeel.net)

    View original source ↗Source licence: CC BY-SA 4.0

    Cropped to the pelvis and legs, padded and resized for display.

  • The Nariokotome Boy, World Museum Liverpool

    Rept0n1x

    View original source ↗Source licence: CC BY-SA 3.0

    Cropped to the lower legs and acrylic stand-in feet; resized for display.

  • Drimolen Main Quarry

    Andy Herries

    View original source ↗Source licence: CC BY-SA 4.0

    Cropped to exclude the sign; resized for display.

  • DNH 127 cranial fragment — Figure 8

    Jesse M. Martin, A. B. Leece, Stephanie Baker, Andy I. R. Herries and David S. Strait

    View original source ↗Source licence: CC BY 4.0

    Figure extracted and cropped to the five specimen views and scale bar; caption omitted; resized for display.

    © 2026 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

  • Teppo works up a sweat in early Spring

    Don Wright

    View original source ↗Source licence: CC BY 2.0

    Cropped to the horse's head and neck, excluding the rider; resized for display.

  • Turkana Boy cast, American Museum of Natural History

    Vicpeters

    View original source ↗Source licence: CC BY 4.0

    Cropped around the skeleton, placed on a dark ground and resized for display.

  • Earth normal map, 2K

    Solar System Scope

    View original source ↗Source licence: CC BY 4.0

    Normal-map values converted into relief hillshade, projected and composited into the Africa maps.

    Textures by Solar System Scope (solarsystemscope.com), CC BY 4.0

  • Natural Earth countries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Selected, projected and styled for the Africa map's land mask, coastline and country outlines.

  • Natural Earth lakes, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Selected, projected and styled for the Africa map; Lake Turkana enlarged about its centre for legibility.

  • Natural Earth countries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Selected, projected and styled for the Africa map's land mask, coastline and country outlines.

  • Natural Earth lakes, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Selected, projected and styled for the Africa map; Lake Turkana enlarged about its centre for legibility.

Stock footage

38 items

Licensed stock footage used in this film, with each item’s creator and source page.

Research references

Selected sources from the episode’s research and scientific figures.

  1. Herries et al. 2020, Science ↗
  2. Martin et al. 2026 ↗
  3. Ward et al.2015 ↗
  4. Churchill and VanSickle2017 ↗
  5. Simpson et al.2008 ↗
  6. Gona team's institutional account ↗
  7. Brown, Harris, Leakey and Walker1985 ↗
  8. Dean and Smith2009 ↗
  9. Smithsonian ↗
  10. Bastir et al.2020 ↗
  11. Schiess and Haeusler2013 ↗
  12. Schiess et al.2014 ↗
  13. Yost et al.2021 ↗
  14. Pontzer2007 ↗
  15. Sockol, Raichlen and Pontzer2007 ↗
  16. Bates et al., *Running performance in Australopithecus afarensis* ↗
  17. Holowka et al.2026 ↗
  18. Morin and Winterhalder2024 ↗
  19. Pickering and Bunn2007 ↗
  20. Baker2019, *Physiology of sweat gland function* ↗
  21. 2015 heat-exercise consensus ↗
  22. Kamberov et al.2018 ↗
  23. PMC ↗
  24. Aldea et al.2021 ↗
  25. Ruxton and Wilkinson2011 ↗
  26. Reed et al.2007 ↗
  27. Rogers, Iltis and Wooding2004 ↗
  28. Jablonski and Chaplin2010 ↗
  29. Borradale et al.2014 ↗
  30. Crawford et al.2017 ↗
  31. Hatala et al.2024 ↗
  32. Hatala et al.2026 ↗
  33. Spoor et al.2007 ↗
  34. Domínguez-Rodrigo et al.2013 ↗
  35. Gibbon et al.2014 ↗
  36. Antón2003 ↗
  37. Hlubik et al.2019 ↗
  38. NHM skeleton/cast photo ↗
  39. cast photo ↗
  40. Nairobi display ↗
  41. Liverpool display ↗
  42. model deposit ↗
  43. FE22 models ↗
  44. GaJi10 deposit ↗
  45. Drimolen Main Quarry ↗
  46. https://commons.wikimedia.org/wiki/File:Em_-_Homo_erectus,_Turkana_boy_-_1.jpg),2639×3958 ↗
  47. https://commons.wikimedia.org/wiki/File:Turkana_boy_cast.jpg),3024×4032 ↗
  48. https://commons.wikimedia.org/wiki/File:Turkana_Boy_at_Nairobi_National_Museum.jpg),4000×6000 ↗
  49. https://commons.wikimedia.org/wiki/File:The_Nariokotome_Boy,_World_Museum_Liverpool.JPG),3240×4320 ↗
  50. https://commons.wikimedia.org/wiki/File:Drimolen_Main_Quarry.jpg),3264×2176 ↗
  51. Warrener2017 ↗
  52. Wood and Collard-related transition review ↗
  53. Will et al.2015 ↗
  54. Dingwall2013 ↗
  55. Hatala2016 ↗
  56. Grine et al. ↗
  57. https://pubmed.ncbi.nlm.nih.gov/25747316/ ↗
  58. https://doi.org/10.1002/ar.70100)): ↗
  59. Samim et al. ↗
  60. Cunningham et al.2018 ↗
  61. Baab2025 ↗
  62. Bramble and Lieberman2004 ↗
  63. Lieberman et al.2007 reply ↗
  64. https://doi.org/10.17638/datacat.liverpool.ac.uk/2831 ↗
  65. https://livrepository.liverpool.ac.uk/3188008/ ↗
  66. full text ↗
  67. McDonald et al.2009 ↗
  68. Aldea et al. ↗
  69. Dávid-Barrett and Dunbar2016 ↗
  70. *Complementary evolution of coding and noncoding sequence underlies mammalian hairlessness* ↗
  71. Lasisi et al.2023 ↗
  72. Jablonski and Chaplin2000 ↗
  73. review of pigmentation, vitamins and UV ↗
  74. Harding et al.2000 ↗
  75. Bennett et al.2009 ↗
  76. Cazenave et al.2026 ↗
  77. *The hominin fossil record of the Omo-Turkana Basin* ↗
  78. Malherbe et al. ↗
  79. Lepre et al.2011 ↗
  80. Berna et al.2012 ↗
  81. https://digitalcommons.usf.edu/kip_articles/1140/ ↗
  82. https://commons.wikimedia.org/wiki/File:Turkana_Boy.jpg ↗
  83. https://commons.wikimedia.org/wiki/File:Turkana_Boy_at_the_American_Museum_of_Natural_History.jpg ↗
  84. https://africanfossils.org/hominids/knmwt-15000-c ↗
  85. https://sketchfab.com/3d-models/turkana-boy-homo-erectus-3d2174c04bcc4be6922c0160bbc34047 ↗
  86. https://sketchfab.com/3d-models/turkana-boy-homo-erectus-a-pose-c505b065d1d3444392f3279abc398ea0 ↗
  87. https://commons.wikimedia.org/wiki/File:Kenya_Aerial_2009-08-27_14-26-44.JPG ↗
  88. https://elements.envato.com/lioness-licks-mouth-and-looks-out-across-wildernes-W67FW8L ↗
  89. https://elements.envato.com/close-up-of-a-panting-dog-resting-in-an-animal-far-Y3Y3LWT ↗
  90. https://elements.envato.com/a-chimpanzee-walking-on-all-fours-over-grassy-sava-BGSX4RD ↗
  91. https://elements.envato.com/oryx-antelope-in-the-wild-AMLX4VA ↗
  92. https://elements.envato.com/small-herd-of-springbok-seeking-shelter-in-the-sha-KCGVW5Z ↗
  93. https://elements.envato.com/african-american-woman-in-sportswear-resting-on-pr-NWLURTR ↗
  94. https://elements.envato.com/woman-headphones-and-tired-runner-in-city-wipe-swe-AQ4RW6W ↗
  95. https://elements.envato.com/flamingo-lake-view-in-lake-turkana-central-island-YXMZBMR ↗
  96. https://elements.envato.com/one-of-the-pond-herons-found-in-thailand-which-dis-CUYY5Q4 ↗
  97. https://www.youtube.com/watch?v=FHZ_-yl7vCU ↗
  98. https://www.youtube.com/watch?v=826HMLoiE_o ↗
  99. https://x.com/PNASNews/status/2082556990471995783 ↗
  100. https://x.com/kevinhatala/status/1862212196115095634 ↗

Music

  • Original score
    AgentHouse · Project-made score (From Cosmos to Civilization score catalog v4 with bespoke opening and closing)
    Impulse responses: Detmold University of Music SRIR database, CC BY 4.0.
Footage and image usage

Credits and usage times retained from the published edition or its production credit record. Where present, times identify visual appearances, not documentary chapters. Source and licence corrections are listed in the visual credits above.

  • Wikimedia Commons
  • 120 - source: Original source ↗
  • Andy Herries
  • Don Wright
  • Emőke Dénes - source: Original source ↗
  • Jesse M. Martin, A. B. Leece, Stephanie Baker, Andy I. R. Herries and David S. Strait
  • Joshua Stevens / NASA Earth Observatory; Landsat data from the U.S. Geological Survey
  • Karl T. Bates, Sian McCormack, Evie Donald, Samuel Coatham, Charlotte A. Brassey, James Charles, Thomas O’Mahoney, Pasha A. van Bijlert and William I. Sellers
  • Kevin G. Hatala, Neil T. Roach, Anna K. Behrensmeyer, Peter L. Falkingham, Stephen M. Gatesy, Erin Marie Williams-Hatala, Craig S. Feibel, Ibrae Dalacha, Martin Kirinya, Ezekiel Linga, Richard Loki, Apolo Alkoro Longaye, Malmalo Longaye, Emmanuel Lonyericho, Iyole Loyapan, Nyiber Nakudo, Cyprian Nyete and Louise N. Leakey
  • Kevin G. Hatala, Neil T. Roach, John W. K. Harris, Purity Kiura, Emmanuel K. Ndiema, Ben Sila, David Kipkebut, Joyce Waweru, Philiphine Kisale, Apolo Alkoro Longaye, Hilary Sale and Anna K. Behrensmeyer
  • Markus Bastir, Daniel García-Martínez, Nicole Torres-Tamayo, Carlos A. Palancar, Benoît Beyer, Alon Barash, Chiara Villa, Juan Alberto Sanchis-Gimeno, Alberto Riesco-López, Shahed Nalla, Isabel Torres-Sánchez, Francisco García-Río, Ella Been, Asier Gómez-Olivencia, Martin Haeusler, Scott A. Williams and Fred Spoor
  • Natural Earth - sources: Original source ↗ Original source ↗
  • Predatorywasp
  • Rept0n1x
  • Solar System Scope - source: Original source ↗
  • Suyash Dwivedi
  • Vicpeters
  • Original animations and figures created by this channel.
  • Wikimedia Commons — 4:49-4:57
  • 120 — 3:13-3:35, 3:35-3:39, 5:22-5:25
  • 21aerials — 6:54-6:58
  • AmazingAerial — 0:50-0:59, 14:01-14:19
  • Andy Herries — 2:34-2:36
  • ATWStock — 0:06-0:10, 4:24-4:31
  • BlackBoxGuild — 0:00-0:06, 0:10-0:14, 1:33-1:39, 4:31-4:43, 5:32-5:46, 6:26-6:32, 7:27-7:30, 8:44-8:48, 9:11-9:18, 9:44-9:54, 11:57-12:05, 12:27-12:37
  • cloudyew — 10:57-11:04
  • DepictionImages — 5:58-6:07, 6:07-6:11
  • Don Wright — 6:58-7:02
  • ED-DAHBY — 6:21-6:26, 9:23-9:30
  • Emőke Dénes — 0:40-0:50, 1:14-1:26, 3:26-3:35, 3:35-3:39, 5:22-5:25
  • feng570423 — 0:14-0:19, 6:18-6:21, 10:53-10:57
  • forrestbro — 0:25-0:29, 4:43-4:49
  • Hangtime-Media — 7:49-7:54, 8:26-8:29
  • ivanves88 — 6:11-6:18
  • Jesse M. Martin, A. B. Leece, Stephanie Baker, Andy I. R. Herries and David S. Strait — 2:36-2:46
  • Joshua Stevens / NASA Earth Observatory; Landsat data from the U.S. Geological Survey — 10:39-10:44
  • Karl T. Bates, Sian McCormack, Evie Donald, Samuel Coatham, Charlotte A. Brassey, James Charles, Thomas O’Mahoney, Pasha A. van Bijlert and William I. Sellers — 4:57-5:10, 5:14-5:22
  • Kevin G. Hatala, Neil T. Roach, Anna K. Behrensmeyer, Peter L. Falkingham, Stephen M. Gatesy, Erin Marie Williams-Hatala, Craig S. Feibel, Ibrae Dalacha, Martin Kirinya, Ezekiel Linga, Richard Loki, Apolo Alkoro Longaye, Malmalo Longaye, Emmanuel Lonyericho, Iyole Loyapan, Nyiber Nakudo, Cyprian Nyete and Louise N. Leakey — 11:12-11:26
  • Kevin G. Hatala, Neil T. Roach, John W. K. Harris, Purity Kiura, Emmanuel K. Ndiema, Ben Sila, David Kipkebut, Joyce Waweru, Philiphine Kisale, Apolo Alkoro Longaye, Hilary Sale and Anna K. Behrensmeyer — 12:05-12:17
  • ManuMata — 7:02-7:11
  • Markus Bastir, Daniel García-Martínez, Nicole Torres-Tamayo, Carlos A. Palancar, Benoît Beyer, Alon Barash, Chiara Villa, Juan Alberto Sanchis-Gimeno, Alberto Riesco-López, Shahed Nalla, Isabel Torres-Sánchez, Francisco García-Río, Ella Been, Asier Gómez-Olivencia, Martin Haeusler, Scott A. Williams and Fred Spoor — 3:39-3:53
  • Natural Earth — 2:19-2:34, 2:46-3:09, 13:23-13:36
  • Patramansky — 6:41-6:48
  • Predatorywasp — 0:59-1:01
  • Rept0n1x — 10:34-10:39
  • slowmotiongli — 5:55-5:58, 10:44-10:53
  • smrnvfilm — 5:25-5:32
  • Solar System Scope — 2:19-2:34, 2:46-3:09, 13:23-13:36
  • Suyash Dwivedi — 10:10-10:19
  • towfiqu_barbhuyia — 6:39-6:41
  • Vicpeters — 1:01-1:07
  • VictorVice — 6:48-6:54
  • vladimirgorlov2 — 0:19-0:25, 13:51-14:01
  • volv52 — 6:32-6:39
  • Wavebreakmedia — 0:29-0:35, 9:30-9:38
  • YuriArcursPeopleimages — 8:29-8:38

How this film was made

Created and editorially directed by Anders Lunde using a custom production system developed over six months. AI assists research, drafting, programming, and visual production; I review and edit the material and make the final editorial decisions. Narration uses text-to-speech. Visuals combine custom-built scientific animations, AI-generated reconstructions, and credited scientific imagery.

Generated reconstructions illustrate scientific interpretations. They are distinct from photographs, specimens, and measured data.

More about the creator and production →