Geoscience Reference
In-Depth Information
3,000
40,000 Cal. A daily consumption of about 1 kg per capita
could be assumed for the humans living in relatively warm climates. In northern
regions
4,000 and 30,000
-
-
rewood consumption was considerably higher. Fire could be used for
heating, cooking, lighting, and for protection against wild animals. Although, with
re, Calories per head drastically increased from 2,000 to 3,000
4,000 per day or
-
more, that is 5
ciency in its use was very low. The useful
energy exploited by the population did not exceed 5 % of its Calories, the rest being
lost in the air.
6 GJ per year, the ef
-
1.3.3 The Third Age: Agriculture
During the Mesolithic, the end of glaciations and the rise in temperature enabled
humans to increase the cultivation of vegetables and particularly cereals. The
overall availability of energy in the form of food increased dramatically and sup-
ported the growth of population. In per capita terms, the perspective is different.
Since population increased rapidly in the agricultural regions of the World, avail-
ability of food per head did not increase. A diet based on cereals represented a
deterioration, as is witnessed by the decrease in stature following the spread of
agriculture. Agriculture, as the main human activity, progressed quite slowly, if we
compare the diffusion of this technological conquest to the following ones. From
the Near East, where primarily developed 10,000 years ago, agriculture progressed
towards Europe at the speed of 1 km per year. Within 3,000 years, agriculture
reached northern Europe. At the same time, the new economic system was
spreading from northern China and central America, the regions of the world where
agriculture independently developed at the same time or a little later than in the
Near East.
A new development in the agricultural transition took place during a second
phase: from about 5,000 years until 3000 BCE. The period can be considered as a
true revolution. The fundamental change was represented by the taming of animals,
(oxen, donkeys, horses and camels), and their utilization in agriculture and trans-
portation. Humans
energy endowment was rising. If we consider a working animal
as a machine and divide his daily input of energy as food
'
—
among the humans who employed him, consumption per head may have increased
by 20
—
about 20,000 Cal
50 % or more, according to the ratio between working animals and human
beings; which is not easy to de
-
ne for these distant epochs. Only about 15 % of this
input represented, however, useful energy, that is energy converted into work.
During this age, several innovations allowed a more ef
cient utilization of
'
humans
power, fuels and animals; e.g. the wheel, the working of metals, pottery,
the plough, and the sail. The sail was previously used, but it only spread widely
during this revolutionary epoch. The use of wind was the
rst example of the
utilization of a non-organic source of energy, not generated by the photosynthesis
of vegetables. Labour productivity rose markedly. Even though some changes in
the agricultural energy system also took place in the following centuries, technical
