ENERGY FLOW DATA FROM NUŅOA, PERU (Thomas, 1976)
1. Rankings of main crop options by efficiency, hardiness, and use.
| Crop Type | Crop Species |
Energy
Ratio |
Percentage of Families Using Crop |
Crop Hardiness |
| TUBERS: | Potato |
8:1 |
92 |
High |
Oca |
4:1 |
5 |
Intermediate |
|
Isano |
3:1 |
18 |
Intermediate |
|
Ulluco |
3:1 |
9 |
Intermediate |
|
| GRAINS: | Quinoa |
22:1 |
98 |
High |
Canihuya |
15:1 |
64 |
High |
|
Barley |
8:1 |
24 |
Low |
2. Expenditures and returns for average Nunoa family of six.
| Activity type | Expenditures |
Returns |
Return
Ratio |
| Agriculture | 52,000 |
595,000 |
11.5 |
| Herding | 384,000 |
760,000 |
2.0 |
| Herding + Exchangea | 436,000 |
3,461,000 |
7.9 |
aOf total herd production (760,000 kcal), 222,000 kcal are consumed by family, while the remaining 538,000 kcal are exchanged in markets for 2,644,000 kcal of imported high-energy foods, plus additional goods.
Source: R. Brooke Thomas (1976), "Energy flow at high altitude." In Man in the Andes, ed. P. T. Baker and M. A. Little, pp. 379-404. Stroudsburg, PA.: Dowden, Hutchinson and Ross.
SOME TRENDS IN HUMAN ENERGY FLOW
1. Estimated Energy Harvested per Capita in Different Subsistence Systems
| Economic Stage | Energy Harnessed (kcal/person/day) |
|
| Early hominids | 2,000 | |
| Hunter-gatherers with fire | 4,000 | |
| Neolithic farmers with domesticated animals | 12,000 | |
| Pre-industrial plow or irrigation agriculture | 24,000 | |
| Early industrial England (ca. 1850) | 70,000 | |
| Contemporary industrial society (U.S., 1970) | 230,000 | |
Source: E. Cook (1971) The flow of energy in industrial society. Scientific American 224(3): 134-48.
2. Energy production, efficiency, and density trends by subsistence system.
| Subsistence type (specific example) | Efficiency Ratio |
Efficiency Rate |
Population Density |
| Hunter-gatherer (!Kung San, S. Africa) | 9.6 | 1300 | 0.5 |
| Swidden (Tsembaga, New Guinea) | 9.8 | 1320 | 64 |
| (Tsembaga without pigs) | 18.0 | 2550 | -- |
| Hoe agriculture (Genieri, W. Africa) | 11.2 | 1530 | 88 |
| Hoe agriculture + herding (Nuņoa, Peru) | 7.9 | n.d. | n.d. |
| (Nuņoa without herding) | 11.5 | n.d. | n.d. |
| Irrigation agriculture (China, 1940's) | 53.5 | 7870 | 500 |
| Mechanized agriculture (U.S. corn, 1970) | 900 | n.d. | 57 |
| (including fossil fuel consumption) | 2.8 | n.d. | -- |
Efficiency ratio = kcal harvested/kcal expended
Efficiency rate = (kcal harvested - kcal expended)/labor time
Population density = people/square mile
Sources: M. Harris (1975) People, Culture and Nature; R. B. Thomas (1976) in Man in the Andes (ed. Baker and Little); D. Pimentel et al. (1973) Science 182:443-449; M. A. Little and G. Morren (1976) Ecology, Energetics, and Human Variability.