that many human subsistence activities are
energetically costly, and that tasks associated
with farm work bear marginally higher costs
than those associated with foraging (includ-
ing walking) (Fig. 5).
Net energy availability (Ei) scaled by fat-free
body mass ( 1 , 24 ) was generally greater among
humans than other great apes, especially for
Tsimane (Fig. 2). Human subsistence, and par-
ticularly strategies including farming, thus yields
moreenergythatcanbeusedbythebodyfor
diverse purposes other than subsistence, even
though humans spend a greater absolute pro-
portion of their TEE on subsistence (Fig. 6).
This greater net energy availability likely enables
Kraftet al.,Science 374 , eabf0130 (2021) 24 December 2021 4 of 13
0
5
10
15
20
Orangutan
Gorilla Chimp Hadza Tsimane
Foraging efficiency (F)
A
0
500
1000
1500
2000
Orangutan
Gor
illa
Chimp Hadza Tsimane
Return rate (R
), kcal/hrn
Female
Male
B
Fig. 3. Energy spent on subsistence across species/populations.(A) Energy acquired per unit energy; (B) energy acquired per unit time. Values represent posterior
medians ± 95% HDPI (Tsimane/Hadza) or means ± 95% CI (all others). Tsimane and Hadza estimates represent population estimates for a 40-year-old individual.
0
200
400
600
20 40 60
Age (years)
Energy cost (kcal/day)
Activity
Firewood and water collection
Chopping
Climbing
Eating
Manufacture
Food processing
Walking (during foraging)
Hadza: Men
0
200
400
600
20 40 60
Age (years)
Energy cost (kcal/day)
Activity
Firewood and water collection
Digging
Eating
Manufacture
Food processing
Walking (during foraging)
Hadza: Women
0
200
400
600
20 40 60
Age (years)
Energy cost (kcal/day)
Activity
Firewood and water collection
Gardening
Harvest
Eating
Manufacture
Food processing
Hunting/other foraging
Fishing
Tsimane: Men
0
200
400
600
20 40 60
Age (years)
Energy cost (kcal/day)
Activity
Firewood and water collection
Gardening
Harvest
Eating
Manufacture
Food processing
Hunting/other foraging
Fishing
Tsimane: Women
Fig. 4. Subsistence costs for Hadza and Tsimane over the life course.Costs (kcal/day) reflect the time that individuals of different ages spend on activities as
well as the relative energetic costs of engaging in those activities.
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