The species in which the big brain change occurred, as well as evidence for key behavior that we think of as original in Homo sapiens, did not arise in Homo sapiens, but in Homo erectus.
Homo erectus made tools, hunted, utilized fire and built semi-permanent camps. It possessed a modern pelvis, experienced premature birth and an extended childhood. By 700,000 years ago its brain capacity had increased, averaging 900 -1100 cc (possibly larger) which is within the range of modern people. Male stature was about 5′ 9″ and a decrease in sexual dimorphism occurred. Its nasal aperture projected forward, indicating the first external human nose.
Tropical forests have little nutritionally valuable food; the expansion of grasslands that followed ice age climate changes provided an improved diet of animal protein. This change in diet spurred brain growth – a diet high in fat and protein preceded ‘growing’ a big brain.
The loss of forested areas wasn’t a loss in terms of human evolution – those individuals who seized the opportunity to occupy a better nutritional environment by scavenging the savannah for dead animals or the remains of predator kills, ate their way to bigger and better brains – which led to hunting, which provided more and better food. A feedback cycle operated between humans and the environment.
Homo sapiens (archaic) (also Homo heidelbergensis) – A ‘species’ which seems to be an artificial wedge placed between Late Homo erectus / Archaic Homo sapiens.
Archaic forms of Homo sapiens first appear about 500,000 years ago. The term covers a diverse group of skulls which have features of both Homo erectus and modern humans. The brain size is larger than erectus and smaller than most modern humans, averaging about 1200 cc, and the skull is more rounded than in erectus. The skeleton and teeth are usually less robust than erectus, but more robust than modern humans. Many still have large brow ridges and receding foreheads and chins. There is no clear dividing line between late erectus and archaic sapiens, and many fossils between 500,000 and 200,000 years ago are difficult to classify as one or the other.
Classic Neanderthal Sites
The ability to control fire is unlikely to have developed in tropical forests, but grasslands are frequently burned by lightning-ignited fires. The challenge of evading wild fires, and the opportunity to obtain “cooked” carcasses of animals killed by fire, may have prompted the practice of cooking food, which makes it easier to eat and also preserves meat. Driving animals into ambush by setting fires became a hunting tactic. Observing a new suite of prey and predator interaction (solitary – like those between big cats and herd animals, and pack behavior – like those between canids and their prey) offered tactics and strategies to be copied. The human ability to copy not only other humans, but all of nature is key to understanding human advantage.
The extensive migrations of Homo erectus, which took it into the varied landscapes of Europe and Asia, produced groups of Homo erectus that adapted to non-tropical regions. Modern humans demonstrate both the physical and cultural adaptations that resulted as Homo erectus expanded its range. Homo erectus did not wait around in Africa for enough “intelligence” to move on; their migrations induced technical and cultural inventions that led to a more controlled and less perilous existence in diverse environments.
Homo erectus / Homo neandertalensis: Homo neanderthal looks suspiciously like Homo erectus on steroids.