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All episodes/Episode 7.2

Episode 7.2 · 15 min

How We Came to Walk Upright

How did apes that still climbed trees begin walking on two legs? Follow the evidence from Toumaï, Ardi, Lucy, and the Laetoli footprints to see how upright walking assembled piece by piece over millions of years in wooded Africa—long before big brains or stone tools—and why footprints reveal behavior that bones can only suggest.

Watch this film on YouTube ↗

Visual credits

20 sources

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

  • Sahelanthropus tchadensis skull cast

    Rama

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

    Converted to PNG and resized for video.

  • Lucy skeleton cast on black background

    120

    View original source ↗Source licence: CC BY 2.5

    Converted to PNG and resized; animated crops, zoom and amber pelvis outline added in the explanatory sequences.

  • Laetoli footprints replica

    Momotarou2012

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

    Converted to PNG and resized for video.

  • Ardi remains from Aramis, Ethiopia

    Sailko

    View original source ↗Source licence: CC BY 3.0

    Converted to PNG and resized for video.

  • Ardipithecus ramidus reconstructed skull cast

    Rama

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

    Converted to PNG and resized for video.

  • Lucy skeleton cast at Naturmuseum Senckenberg

    Daderot

    View original source ↗Source licence: CC0 1.0

    Converted to PNG and resized for video.

  • Toumaï cranium cast, TM 266-01-060-1

    Didier Descouens

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

    Converted to PNG and resized for video.

  • Laetoli footprint casts at the Natural History Museum, Vienna

    Wolfgang Sauber

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

    Converted to PNG and resized for video.

  • Laetoli Site G trackway cast elevation model — Figure 11

    Fidelis T. Masao, Elgidius B. Ichumbaki, Marco Cherin, Angelo Barili, Giovanni Boschian, Dawid A. Iurino, Sofia Menconero, Jacopo Moggi-Cecchi and Giorgio Manzi

    View original source ↗Source licence: CC BY 4.0

    Figure cropped from the paper; header and caption omitted; animated pan and zoom added.

    Copyright Masao et al. Published in eLife 5:e19568 (2016).

  • Toumaï unreconstructed cranium cast, side and top views

    Didier Descouens

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

    Cropped from the original multi-view photograph and resized for video.

  • Laetoli Site G trackway map

    Chartep

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

    Right-hand northern panel cropped from the original map; animated amber highlights added.

  • Sahelanthropus cranium, ulna and femur — Figure 1B

    Scott A. Williams, Xue Wang, Isabella Araiza, Jordan S. Guerra, Marc R. Meyer and Jeffrey K. Spear

    View original source ↗Source licence: CC BY 4.0

    Panel B cropped from Figure 1; animated reframing, zoom, amber traces and schematic highlight ring added.

    Copyright © 2026 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).

  • Sahelanthropus fossils compared with chimpanzee and human — Figure 1

    Scott A. Williams, Xue Wang, Isabella Araiza, Jordan S. Guerra, Marc R. Meyer and Jeffrey K. Spear

    View original source ↗Source licence: CC BY 4.0

    Figure panels A–C cropped from the paper; caption omitted; animated highlighting and changes in panel brightness added.

    Copyright © 2026 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution License 4.0 (CC BY).

  • Laetoli footprint G1-37 contour and profile — Figure 1C

    David A. Raichlen, Adam D. Gordon, William E. H. Harcourt-Smith, Adam D. Foster and Wm. Randall Haas, Jr.

    View original source ↗Source licence: CC BY 2.5

    Panel C cropped from Figure 1; resized for video with an animated amber ring highlighting the big-toe region.

    © 2010 Raichlen et al. From “Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics,” PLoS ONE 5(3): e9769.

  • Earth normal map

    Solar System Scope

    View original source ↗Source licence: CC BY 4.0

    Normal-map texture converted into relief hillshading, recoloured, projected and cropped for the Africa find-point maps.

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

  • Natural Earth countries, coastlines and land boundaries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Projected, cropped and styled for the Africa find-point map.

  • Natural Earth countries, coastlines and land boundaries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Projected, cropped and styled for the Africa map and Chad zoom.

  • Natural Earth countries, coastlines and land boundaries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Projected, cropped and styled for the Africa map highlighting Ethiopia.

  • Natural Earth countries, coastlines and land boundaries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Projected, cropped and styled for the Africa map highlighting Tanzania.

  • Natural Earth countries, coastlines and land boundaries, 1:50 million

    Natural Earth

    View original source ↗Source licence: Public domain

    Projected, cropped and styled for the Africa map highlighting Tanzania and Ethiopia.

Stock footage

35 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. Williams et al., 2 January 2026 ↗
  2. White et al. 2009, 10.1126/science.1175802 ↗
  3. Wiseman 2023 ↗
  4. Vignaud et al. 2002 ↗
  5. 2015 synthesis ↗
  6. Drummond-Clarke et al. 2022 ↗
  7. Deino chapter ↗
  8. Masao et al. 2016 ↗
  9. current PDF ↗
  10. conservation-program summary ↗
  11. 2015 ↗
  12. 2019 Manitoba thesis ↗
  13. 2025 review of lower beds ↗
  14. Raichlen et al. 2010 ↗
  15. Hatala, Gatesy and Falkingham 2023 ↗
  16. primary abstract ↗
  17. primary record/full-text index ↗
  18. 2021 ↗
  19. 2008 ↗
  20. Daver et al. 2022 ↗
  21. Cazenave et al., online 2024, volume 2025 ↗
  22. Macchiarelli et al. 2020 ↗
  23. Science Media Centre's directly solicited reactions ↗
  24. Le Fur et al. 2009 ↗
  25. pelvis/femur ↗
  26. foot ↗
  27. Prang et al. 2021 ↗
  28. Prang et al., 15 October 2025 ↗
  29. Lovejoy's pelvis review ↗
  30. Kim et al., 2016, 10.1016/j.pmrj.2015.06.005 ↗
  31. Lovejoy hip/thigh review ↗
  32. Venkadesan et al. 2020 ↗
  33. Senevirathne et al. 2025 ↗
  34. Kozma et al. 2018 ↗
  35. PMC article ↗
  36. author's institutional abstract ↗
  37. Sockol, Raichlen and Pontzer 2007 ↗
  38. Carvalho et al. 2012 ↗
  39. Thorpe, Holder and Crompton 2007 ↗
  40. Hunt 1994 ↗
  41. Walter 1994 ↗
  42. Smithsonian's species record ↗
  43. Ward et al. 2011 ↗
  44. Green and Alemseged 2012 ↗
  45. primary PubMed abstract ↗
  46. “A 4.3-million-year-old Australopithecus anamensis mandible…” (2024) ↗
  47. Haile-Selassie et al. 2019 ↗
  48. Hershkovitz et al. 2026 ↗
  49. Haile-Selassie et al. 2025 ↗
  50. Harmand et al. 2015 ↗
  51. https://doi.org/10.1130/0091-7613(1994)022%3C0006:AOLATF%3E2.3.CO;2 ↗
  52. Science Advances figure post ↗
  53. project page ↗
  54. Indexed original report URL ↗
  55. Musiba et al. 2008 ↗
  56. 2011 ↗
  57. CC BY 4.0 PDF ↗
  58. Laetoli replica ↗
  59. Crompton et al. 2012 ↗
  60. Hatala, Demes and Richmond 2016 ↗
  61. Bennett et al. 2016 ↗
  62. Bennett et al. 2009 ↗
  63. 2024, Early Hominin Movement Patterns at Laetoli ↗
  64. 2025 gait-synchronization study ↗
  65. 2026 ↗
  66. Toumaï skull ↗
  67. habitat ↗
  68. Simpson et al. 2019 ↗
  69. Cerling et al. 2010 ↗
  70. White et al.'s reply ↗
  71. Ardi museum display ↗
  72. Ardi drawing ↗
  73. specimen record ↗
  74. https://commons.wikimedia.org/wiki/File:Resti_di_ardipithecus_ramidus_detto_ardi,_da_aramis_(afar),_4,4_milioni_di_anni_fa_01.jpg ↗
  75. 2024 field study ↗
  76. sex-difference study ↗
  77. Bossou/Kyoto source-owner page ↗
  78. BossouChimpanzee dataset research ↗
  79. https://doi.org/10.1073/pnas.0703267104): ↗
  80. https://doi.org/10.1126/science.1140799): ↗
  81. Lucy black-background cast ↗
  82. Laetoli contours ↗
  83. Orrorin femur ↗
  84. Wild Borneo orangutan video ↗
  85. Lake Baringo ↗
  86. bonobo eating ↗
  87. YNKLGNP ↗
  88. F8X2T6H ↗
  89. romickvesely, 5XURCJP ↗
  90. MorphoSource project 000752600 ↗
  91. Figshare collection 6672258 ↗
  92. Human Footprint exhibit ↗
  93. Lucy/Laetoli museum page ↗
  94. https://commons.wikimedia.org/wiki/File:Early_Morning_at_Lake_Baringo,_Rift_Valley,_Kenya_(34004528696).jpg ↗

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.

  • 120 - source: Original source ↗
  • Chartep - source: Original source ↗
  • Daderot
  • David A. Raichlen, Adam D. Gordon, William E. H. Harcourt-Smith, Adam D. Foster and Wm. Randall Haas, Jr. - source: Original source ↗
  • Didier Descouens
  • Fidelis T. Masao, Elgidius B. Ichumbaki, Marco Cherin, Angelo Barili, Giovanni Boschian, Dawid A. Iurino, Sofia Menconero, Jacopo Moggi-Cecchi and Giorgio Manzi - source: Original source ↗
  • Momotarou2012
  • Natural Earth - source: Original source ↗
  • Rama
  • Sailko
  • Scott A. Williams, Xue Wang, Isabella Araiza, Jordan S. Guerra, Marc R. Meyer and Jeffrey K. Spear - source: Original source ↗
  • Solar System Scope - source: Original source ↗
  • Wolfgang Sauber
  • Original animations and figures created by this channel.
  • 120 — 11:42-11:46, 12:12-12:20, 12:20-12:27
  • AmazingAerial — 13:46-13:56, 14:18-14:27
  • BlackBoxGuild — 1:33-1:41, 1:41-1:44, 2:35-2:37, 4:03-4:06, 6:12-6:18, 6:39-6:43, 6:43-6:46, 6:46-6:49, 7:10-7:14, 7:14-7:16, 7:46-7:52, 7:52-8:01, 8:10-8:20, 8:20-8:30, 8:34-8:39, 8:46-8:54, 8:54-9:03, 9:03-9:08, 9:08-9:24, 9:30-9:37, 9:48-9:57, 11:14-11:22, 14:09-14:18
  • Chartep — 10:07-10:20
  • Daderot — 11:50-11:56
  • David A. Raichlen, Adam D. Gordon, William E. H. Harcourt-Smith, Adam D. Foster and Wm. Randall Haas, Jr. — 10:29-10:34
  • Didier Descouens — 2:01-2:11, 2:11-2:14
  • Fidelis T. Masao, Elgidius B. Ichumbaki, Marco Cherin, Angelo Barili, Giovanni Boschian, Dawid A. Iurino, Sofia Menconero, Jacopo Moggi-Cecchi and Giorgio Manzi — 10:20-10:29
  • KinoMaster — 4:19-4:28
  • losevideo — 3:22-3:26, 5:07-5:12
  • luxiico — 9:24-9:30
  • MatthewWilliams-Ellis — 6:49-6:59, 8:30-8:34
  • Meh21 — 1:44-1:50
  • Momotarou2012 — 11:22-11:29
  • Natural Earth — 1:24-1:33, 1:50-2:01, 5:25-5:31, 10:03-10:07, 11:40-11:42
  • nskfoto — 4:51-4:54, 4:54-4:57
  • OlgaVELES — 4:57-5:07
  • Rama — 2:33-2:35, 5:39-5:46
  • rassolovstanislavg — 10:43-10:48
  • Sailko — 5:34-5:39
  • Scott A. Williams, Xue Wang, Isabella Araiza, Jordan S. Guerra, Marc R. Meyer and Jeffrey K. Spear — 2:51-3:05, 3:05-3:22, 3:26-3:39
  • ShotHappens — 4:06-4:15
  • Skuridin — 10:37-10:43
  • Solar System Scope — 1:24-1:33, 1:50-2:01, 5:25-5:31, 10:03-10:07, 11:40-11:42
  • VideoKot — 4:15-4:19
  • Wolfgang Sauber — 0:53-1:04

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 →