The capacity for culture, together with human dexterity, led to one particularly important difference between the ecology of our species and that of other mammals. The regular use of fire and the manufacture and use of tools added an extra dimension to the metabolism of human populations – referred to as technometabolism.
Technometabolism is defined as the pattern of flow of energy and materials into, through and out of a human population that results from technological processes. It contrasts with biometabolism, which is the flow of energy and materials into, through and out of human organisms themselves. Of course, some animas use tools, but technometabolism on the scale seen in human populations is a new phenomenon in the history of life on Earth. It is of tremendous significance ecologically and in many other ways.
The use of fire in particular was a development of enormous ecological significance. It was the first example of the regular and deliberate use by humans of extrasomatic energy – energy, that is, which is used outside the human body, as distinct from the somatic energy which is consumed in food and which flows through the human body.
It has been estimated that the introduction of the regular use of fire in human populations approximately doubled the per capita energy use, bringing the average total energy used per day per person (men, women and children) to about 14 MJ: that is, roughly 7 MJ used in biometabolism and 7 MJ in the burning of wood.
In the early farming ecological Phase of human history and in the early urban phase, new technologies were introduced that resulted in some intensification of technometabolism. In particular, there was an input of various metals, especially iron and the combustion of wood as a source of energy for smelting.
There has been an explosive increase in the intensity of technometabolism in ecological Phase 4 of human history – the Exponential Phase or the Anthropocene. Humankind is now using 20,000 times as much extrasomatic energy as was the case when farming began, and 95 per cent of this increase occurred over the past 150 years. Also, vast quantities of many different elements are used in technological processes and in the manufacture of a great range of different kinds of artefacts. The per capita consumption of iron in Australia today is over 1.3 kg per day.
The analysis of flows of materials and energy into, through and out of urban systems has now become an important field in human ecology. An early example is the study of the metabolism of Hong Kong.
Patterns of urban metabolism have an important influence on
the health of human populations and of the ecosystems of the biosphere.
 Newcombe, K,, J. D. Kalma and A. Aston. 1978. The metabolism of a city: the case of Hong Kong. Ambio. Vol. 7, No. 1, pp. 3-15.
Boyden, S., S. Millar, K. Newcombe, B. O’Neill, 1981. The ecology of a city and its people: the case of Hong Kong. ANU Press, Canberra.