This short account has followed the changing relationship with their environment, first of the pre-human bipeds and later of the humans who displaced and succeeded them.
The story started in Africa with the Australopithecines: apes probably in many ways very much like their ape relatives, but who had sacrificed some of their tree-climbing ability, in return for being able to walk and run efficiently on the ground on their back legs only. Their hands were thus set free to throw missiles, wield clubs and of course carry around their young, their weapons, ammunition, food supplies and whatever else was useful to them.
They were intelligent, adaptable and omnivorous but relatively slow and vulnerable; so they probably had less of a problem with food-gathering than with defence. Their young depended on them for protection for many years. Their environment was tropical Africa, full of deadly predators of all shapes and sizes, virtually all of which could run faster than they could and many of which were highly intelligent and very agile climbers: not only the great cats, smaller cats, jackals and hyenas, but snakes, eagles and their own relatives the chimpanzees, all of which, if not prevented, would kill and eat their young. Even in the trees, life had not always been easy; as they increasingly spent more time on the ground, it is hard to understand how they survived at all. But they did.
We think we know how they managed it: unlike every other animal, they defended themselves and their young not with inbuilt weapons - teeth, claws, hooves or horns - but with natural or artificially adapted temporary extensions to their arms - missiles and clubs. They could fight enemies effectively whilst themselves staying out of range of the enemy’s weapons.
These animals lived and diversified for more than two million years; as long a period as has elapsed since they disappeared. They were displaced by animals we call pre-humans - bipeds who were more completely adapted to life on the ground; who could probably climb less well but who made up for it by greater intelligence and perhaps greater skill with their hands. These newcomers - our own closest relatives - could probably throw more effectively and they developed the ability to shape weapons and tools not only from soft materials but from stone, yielding sharp points and edges. They learned how to use fire.
The pre-humans became, over time, better adapted to life outside the tropics. They expanded their territory to include southern Eurasia. Increasingly, their skill with sharp missiles made them feared and avoided by small birds and mammals. They could drive predators away from their young with a barrage of missiles and they probably used the same technique to obtain meat by driving predators off their kills. They looked increasingly like people. But the lives they lived were very different from those of any humans, because they lacked language. They lived in small, exogamous groups, their environment shaped and controlled by the megafauna, above all by the mammoths.
And so life continued and little changed - for literally hundreds of thousands of years.
And then suddenly, quite recently, only about fifty thousand years ago, everything changed. From somewhere in Africa emerged true humans - people who appear to have differed individually little from the pre-humans, but who had language and social organisation. They could communicate detailed information and instructions to one another and organise themselves not in tens but in hundreds or even in thousands. What ten or twenty pre-humans could not achieve together, an army of hundreds of humans could. An army of hundreds, wisely led, was more than equal even to the largest herd of mammoths. New weapons and sophisticated hunting techniques suddenly made the greatest and most powerful mammals vulnerable as never before. The empire of the elephants was challenged. The great tusks of the mammoths became a human raw material.
Within perhaps ten thousand years - only five hundred generations - the newcomers spread from their African origins all over the Eurasian territory of the older pre-humans, and further north. Even the sea was no longer a barrier to them. They fish in it, and voyage in search of new lands to conquer. At the farthest limit of Eurasia, they rowed or sailede beyond the horizon, over fifty miles of sea and discovered Australia - a new continent, a hunter’s paradise, where even the biggest animals were vulnerable and even the most intelligent apparently unaware of danger. Glutting themselves on meat and losing scarcely any of their children to predation, the newcomers rapidly increased in numbers and spread throughout the new land - until their increasing collective appetite encountered a decreasing supply of food. In a continent not well endowed with edible plants, they people through a painful period of famine, and finally settled into a new rhythm, exploiting their mastery of their environment to maximise its yield by the use of fire.
In Eurasia and Africa, the same process was at work, more slowly but still very rapidly in terms of geological time, and with accelerating speed. The mammoths and many other prey animals also in the end proved too vulnerable and were hunted to extinction. As in Australia, so in Eurasia and Africa, people ran very short of food.But here, they found a better answer. They learn to greatly increase the food yield of their environment by turning it into farmland. They took control also of herds of herbivores, defend them against predators and other human hunters and organised them to produce meat, milk, wool and hides in a sustainable way. Much the same thing happened later in America.
All this occurred in perhaps forty thousand years - probably less than one per cent of the time which has elapsed since the appearance of the australopithecines; yet already, under human control, the whole aspect of many parts of the world completely changed. And change accelerated. Human communication became possible, not only throughout communities of living people, but over time and over great distances, by means of writing. Tribes of hundreds or thousands gave way to empires of millions, ruled from cities of tens and even hundreds of thousands. Human mastery of the environment started to include not just the living world but the elemental forces of nature. Despite wars and conflicts, human trade and co-operation became more and more world-encompassing. Most recently the world has been linked everywhere by a complete system of electronic communication.
And still, only about fifty thousand years has elapsed since the first real people emerged from Africa. Only about two thousand generations have lived and died since the dramatic arrival of mankind. If there is such a thing as a miracle, mankind is one.