What first made the first humans different?

For many millions of years, the big cats had been the biggest and most efficient predators anywhere, with hyenas and some reptiles and other large beasts coming rather a long way behind them. Each of these species had their own specific methods of hunting. Some modern cats such as gepards can accelerate to 100 km/h within seconds but they cannot keep this up for more than few minutes. Lions on the other hand are very powerful – and heavy. They compensate their lack of speed with their pride’s clever hunting tactics.

The ancestors of the early humans were omnivorous. They could and would eat anything not actually poisonous that they could find or catch: plants, carrion, living animals of any kind. As hunter-gatherering humans their speciality was flexibility – and long-distance running. As such they had a brain good at spotting unexpected opportunities and were able to react quickly to sudden unexpected opportunities. As early humans became more successful they became taller and also invested more and more energy in an ever-expanding brain. This development probably initially started with t the Australopithecines (see chart below) but it is still ongoing today. No other creature on earth now has a brain as heavy in relation to the size of its body as has Homo sapiens.

Over millions of years, the early ancestors of Homo developed into the most persistent of all persistence hunters. Most hunting animals can run very fast indeed but can do so only in short spurts of few seconds or minutes at most. Others (like hyenas) can be persistent followers of an injured animal but they cannot run for long.The new hominids in the African plains could run for hour after hour behind an injured animal until it was caught. Modern Australian aborigines are said to still occasionally hunt kangaroo in this way.

The new tactics was such a success that it was increasingly reflected in physiological adaptations: the two-legged upright posture which made long-distance running so much more efficient was adapted as permanent gait, sweat glands became much more numerous and more highly developed and the furry body hair was largely dispensed. The change also freed the forelegs for “other uses”. Early humans soon must have discovered that while running they could now also throw stones. It would not have them taken long to refine the new skills into hunting (and fighting with each other) by throwing pointed sticks while running at the same time. As part of making themselves fit for long-distance running, pre- or early-humans also lost most of their body fur and to start to sweat more to balance their body temperature Nor did they need to shiver in the cold night-time caves: all they had to do was to use their prey’s inedible hides to keep warm at night. Such technological progress (initially slow but steadily accelerating ever since) has been a main characteristic of humans ever since.

Toolsoldest-Ethiopia

Despite the hominids’ change to a more active hunting way of life, the early humans never became wholly carnivorous. To they dismay of many modern children, grown up Homo sapiens have remained stubbornly omnivorous (drawing the line at carrion, however) and greens remain widely eaten. Eating anything that is not actively poisonons has proven to be a successful survival strategy.

A pebble tool found in Ethiopia is thought to have been hammered into the shape of a scraper 2.5 million years ago (ref. Angela M.H. Schuster (Rutgers University)

Unbroken pebbles have almost certainly been used as tools (hammers to crack open nuts or as missiles) far in pre-human times, but such early use is practically impossible to prove. Chimpanzees, however, have been observed using pebbles as hammers to crack open nuts.

The scale in the picture is in cm.

Next: Pre-humans and earlier Out-of-Africa migrations