Introduction

No animal spends the day sitting at a computer terminal, so should the lives of office workers be regarded as unnaturally inactive? No wild animal goes out running for the sake of its health, so should some people be regarded as unnaturally active? This chapter tries to put human activity in perspective by comparing it with the activity of other mammals.

Typical human body masses are about 50 kg for adult women and 70 kg for men. Other mammals range from 2g shrews to 6000 kg African elephants (Macdonald, 1984). In making comparisons, differences of size will have to be taken into account.

Quantities such as metabolic rates, speeds of locomotion and distances travelled will be compared, which vary with body size. Comparisons could be limited to animals of similar size to man (for example, leopards, some antelopes and large kangaroos), but if that was done there would be very limited data. It seems better to use data for mammals of all sizes to find out how the measures of activity concerned generally vary with body mass. It will then be possible to predict typical values for mammals of the same mass as man, and compare man with those.

The monotremes (platypus and spiny anteaters) and marsupials (kangaroos, opossums, etc) are in some respects more primitive than the other mammals, which are known as eutherians. Humans are eutherians, and most of the comparisons in this paper are with other eutherians.