One of the many million species, Homo sapiens
is now co-opting about a quarter of all photosynthetic products for its own use.
The words from Paul Ehrlich help us to understand the fascinating, complex and incredible story
of our species after only 200 000 years from its appearance on Earth. Accounting for this pathway is a difficult
task that goes beyond the purposes of our talk. However, we are interested to think about a single aspect of the astonishing changes
that have occurred in the relationship of humankind and nature, the role of energy
use in advances of human civilization. Since its appearance, humankind learned how
to manage increasingly large energy flows. Although the evidence of this behavior has
become manifest only over the past two centuries, its roots lie deep in the Stone Age, at the
early stage of the Paleolithic period. Over a long time period, until the dawning
of industrial revolution, humankind accessed only to natural energy resources: muscular
power from humans and animals, running waters, wind energy and fuels from organic feedstocks.
Early energy uses of humankind were based on biological energy elaborated in human organisms.
Indeed, it was used on external bodies with the aim to modify the environment and obtain
a benefit from it. Three different interactions can be identified:
– direct, acting by contact – direct, acting through an intermediate tool
– indirect, controlling, through technological artefacts, energy flows from external sources, like animals, wind or waters. In the Paleolithic period, energy uses were
limited to the attainment of food through hunting and gathering and the sheltering from
climate and other predators. In preindustrial societies, the progressive
control of the environment from humankind can be described symbolically by three achievements
in energy control. In chronological order, these three milestones
were: technology, control of fire and agriculture. In this context, when we talk about technology
we refer to its broader meaning – that is the skill to build and use tools that are
not available in nature. Early artifacts were used to easily manage
hard daily works such as food preparation, hunting, transportation of heavy objects and
the construction of shelters. These tools were used to transfer muscular power more
efficiently. For example, awls were used to concentrate human muscular force by reducing
contact surfaces. A breakthrough was the control of fire achieved
about 700 000 years ago that radically changed human life. The Greek
myth of Prometheus well represents the impact of this innovation. Indeed, it was so important to be considered by our ancestors like a sacred gift from Gods. The availability of a high temperature heat source entailed important advantages such as cooking, warmth and protection. In fact, high temperatures soften fibers and were able
to destroy toxins of foods that might otherwise have been unusable.
It is worthwhile nothing that through these innovations, humankind did nothing but increase
efficiency in the parasitic use of two groups of biological converters: plants and animals.
Essentially, humans remained parasite although more and more efficiently.
The last achievement of pre-historical societies was agriculture around 11 500 years ago at the end of the last ice age and the beginning of the
Holocene epoch. Agriculture is considered a milestone in human
society in what it describes a shift to intensification. This is the ensemble of new technologies and
lifeways through which humankind harness more resources from a given area of land.
By means of agriculture, humankind was capable to increase the available quantity of plants
and animals, therefore widening energy availability. In fact, human societies could provide their
own and domestic animal’s food by controlling crops. Few key innovations drove early achievements in agriculture. Among the others, it is worth
mentioning domestication, shifting cultivation, use of draft animals, organic fertilizers
and artificial irrigation. All these innovations improved energy productivity
of crops. This quantity is the ratio of the net energy available from food and the energy
expenditure for production. The latter quantity includes for instance food for humans and
animals engaged in production. Energy return on invested energy always exceeded
the value of ten and was most likely around twenty.
The increased pace of technological innovation soon concerned with the use of inanimate energy
from wind and running waters. Even in this case, agriculture productivity had a great
gain since water and wind mills improved flour milling processes. Moreover, wind and running
water energy were used to power early irrigation systems which could supply enough water to
sustain photosynthetic processes for food production. The ability of harvesting wind and water energy was also crucial for sailing. Ships contributed
to early economic development and in general to expand transportation and information capability
of humankind. It is not by chance that past major civilizations flourished close to rivers
or coastlines. Following all these innovations of the Neolithic
period, humans ceased to be simple heterotrophs. Since then, they became increasingly sophisticated
manipulators of solar flows and builders of complex societies.