Our development has been broken down into evolutionary cycles, marking the significant changes as we emerged from ape-like creatures; who subsisted by scavenging; to hunters and gatherers who roamed in search of food; and finally to cultivators who engaged in actual food production.
Darwin’s view of natural history, and that of many others; is based on the principle that offspring from any species had to fight for survival, because of a limited food supply. Therefore, only the strongest made it to adulthood, passing on the traits that made them superior beings, to the next generation.
The popular theory is that early primates were almost rodent like, with only enough brain capacity to see food, climb toward it, grasp it and consume it, while instinctively avoiding danger. Since their diet consisted of leaves, flowers, fruit, insects and birds' eggs, they did not require the specialized teeth found in most mammals.
They lived in trees, so good vision was more important than a sense of smell, which is also better developed in other animals. The process of adapting to climbing trees meant more brain capacity for vision and muscle coordination, and the ability to grasp branches with the front feet to swing the rest of the body forward, evolved naturally into hands.
But if man evolved solely from apes, why are there still apes?
Researchers have answered this by suggesting that all primates, including humans, have a common ancestor that they refer to as the Ramapithecus; who lived about 15 million years ago, during the Miocene. Then, over a period of about ten million years, rainfall declined and large deserts separated the forests of Africa from those of India and east Asia, thereby shrinking the amount of available living space. Consequently, while some remained basically unchanged, a superior band broke away and by four million years ago the Australopithecus, or southern ape, had evolved to the level of hominid.
A hominid is an animal on the human family tree, but what sets them apart from apes is their bipedalism (walking on two legs), not necessarily the size of their brains. The very first hominids had relatively long arms, but as they became better adapted to standing on their own two feet, and no longer needed to climb trees, their arms shortened and their fingers became less curved. They also had thicker dental enamel and smaller canine teeth than their ape ancestors.
The discovery of more than 300 skeletal remains in Ethiopia, believed to be about 2.7 million years old, give us some insight into early mankind. Though only a female skeleton could be reconstructed; dubbed “Lucy”; it provides us with a good indication of how we may have appeared at this stage in our evolution.
In overall body size, brain size and skull shape, Lucy resembled a chimpanzee; but already had many human characteristics; including the ability to walk upright. So, was Lucy merely at an advanced stage of her metamorphosis from ape to human; or an entirely unique species? All indications are that she was in fact, one of our earliest ancestors, who lived on earth when many other species were also finding their way; including foxes, deer, mice, skunks, rattlesnakes, rabbits, squirrels, llamas, cats, bears, weasels, porcupines, snapping turtles, and small mastodons, though many she would not have seen.
Though originally, the emerging human being could only be found in Africa; by about 1.7 million years ago, they began to make an appearance in Asia and parts of Europe, but it was when humans began to adapt to their new environment, that the next stage in our evolution began. Those residing or at least wandering, in various parts of the world, began to adopt superficial physical characteristics, like skin pigment, eye shape, and hair texture, that were biologically transmitted and refined through future generations.
From biological changes brought about through natural selection, came cultural changes, which further separated mankind into unique groups. Early humans may have wandered about in search of food, but would linger where there was an abundance of game, fish and plant life. Population bursts resulted in extended families, who worked together to survive and as these families foraged for food, they joined other families to form tribes.
By then we had evolved memory, made choices, learned, pair-bonded, raised children, and were guided by instinct, experience, and non-verbal tradition. In other words, we lived and communicated as other animals did. Then about 50,000 to 500,000 years ago, symbolic language emerged, which marked the birth of beliefs and a radical shift in human behavior.
100,000 to 120,000 years ago, some of these intellectual bands crossed into the Middle East; and about 50,000 years ago they entered Australia, possibly via a land bridge from Southeast Asia. They brought the Dingo with them, but caused the extinction of Australia's Largest marsupials, reptiles, and flightless birds.
40,000 years ago the first humans arrived in South America and as early as 27,000 years ago, in North America. No doubt future archeological study will alter these times and places, but for now they are a useful tool in tracking the migration of early humans. Mankind was now in a position to exchange ideas with others beyond their own small unit; and innovations, like the use of fire, brought about dramatic changes. It gave them more independence, provided them with light and warmth, and meant that they could continue to socialize and communicate even after nightfall. It also helped to move them up another notch on the food chain, as they used it to frighten large predators out of their caves, and took them over to become their new homes.
The invention of fire also allowed for the heat treating of tools, which created stronger and sharper points, meaning that they could now fell larger game. As a result, humans could expand their horizons, and now that they had the discovered the means to stay warm, tribes began to move further north. The need for vitamin D in these northern climates selected whiter skin which could absorb sunlight better to prevent rickets; a disease to which many of these early northern pioneers succumbed. As for the continuing status of other mammals; the Caribou originated about a million years ago; Polar Bears evolved from the Asian grizzly bear 200,000 years later and the Bison emigrated from Asia into Noerth America for the first time about 400,000 years ago.
