Underground Plant Food Consumption

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Plants that sequester nutrients in underground storage organs (USOs) are staples in many hunter-gatherer diets. Baboons also exploit near surface corms, but do not take deeply buried tubers. With the exception of digging residues that may indicate USO feeding by chimpanzees, no other living hominids are known to use these resources. Australopithecines, however, are characterized by molar enlargement that may reflect heavy USO consumption. The tubers routinely taken by ethnographically known hunter-gatherers include species that young children cannot handle efficiently, requiring them to depend on shares of these resources acquired by others. This observation is the basis for a grandmother hypothesis that links exploitation of tubers with novel fitness opportunities for older females. As their own fertility was ending, food sharing with grandchildren would improve the youngsters’ survival and allow their mothers to shorten birth intervals. The more robust elders who supplied more help had more descendants, resulting in the evolution of longer human life spans and our distinctive form of cooperative breeding. Ecological changes in the Plio-Pleistocene to drier, more seasonal environments would have favored plants with USOs, and the changes outlined above have been hypothesized to mark the appearance and spread of genus Homo. Nutrient availability from some USOs can be improved by cooking. This step in handling increases the return rate advantage for adults compared to children. It is also central to another hypothesis about the evolution of genus Homo, one that emphasizes the wider array of resources that can be consumed with cooking and proposes that the smaller teeth and larger body size of genus Homo are consequences of the advent of this practice roughly two million years ago. Resources collected in quantity for cooking become vulnerable to expropriation. The cooking hypothesis proposes that ancestral females enlisted protectors by forming pair-bonds, which in turn is said to account for reduced sexual dimorphism in Homo compared to the australopithecines.


Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Possible Appearance: 
4,000 thousand years ago
Probable Appearance: 
2,000 thousand years ago
Definite Appearance: 
100 thousand years ago
Related MOCA Topics
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Referenced By:
Topic Certainty
Food Handling Likely
Organized Gathering of Food True
Tool Making Likely
Use of Containers Likely


  1. Tropical forager gastrophagy and its implications for extinct hominin diets, Buck, L, Berbesque J.C., Wood B, and Stringer C , Journal of Archaeological Sciences: Report, 09/2015, (2015)
  2. Mechanical Properties of Plant Underground Storage Organs and Implications for Dietary Models of Early Hominins, Dominy, Nathaniel J., Vogel Erin R., Yeakel Justin D., Constantino Paul, and Lucas Peter W. , Evolutionary Biology, Volume 35, p.159–175, (2008)
  3. Savanna chimpanzees use tools to harvest the underground storage organs of plants., R Hernandez-Aguilar, Adriana, Moore Jim, and Pickering Travis Rayne , Proc Natl Acad Sci U S A, 2007 Dec 4, Volume 104, Issue 49, p.19210-3, (2007)
  4. The rise of the hominids as an adaptive shift in fallback foods: plant underground storage organs (USOs) and australopith origins., Laden, Greg, and Wrangham Richard , J Hum Evol, 2005 Oct, Volume 49, Issue 4, p.482-98, (2005)
  5. The Raw and the Stolen. Cooking and the Ecology of Human Origins., Wrangham, RW, Jones JH, Laden G, Pilbeam D, and Conklin-Brittain N , Curr Anthropol, 1999 Dec, Volume 40, Issue 5, p.567-594, (1999)
  6. Digging and eating of underground plant-parts by wild Japanese monkeys (Macaca fuscata), Iguchi, Motoi, and Izawa Kosei , Primates, Volume 31, p.621–624, (1990)
  7. The Early Hominid Plant-Food Niche: Insights From an Analysis of Plant Exploitation by Homo, Pan, and Papio in Eastern and Southern Africa [and Comments and Reply], Peters, Charles R., O'Brien Eileen M., Boaz Noel T., Conroy Glenn C., Godfrey Laurie R., Kawanaka Kenji, Kortlandt Adriaan, Nishida Toshisada, Poirier Frank E., and Smith Euclid O. , Current Anthropology, Volume 22, p.127-140, (1981)
  8. Bears, Pigs, and Plio-Pleistocene Hominids: A case for the exploitation of below ground food resources, Hatley, Tom, and Kappelman John , Human Ecology, Volume 8, p.371-387, (1980)