Discovering Our Distant Ancestors
Homo erectus or “upright/standing man” evolved from H. habilis. H. erectus became bipedal at least 3 to 4 million years ago, and first moved out of Africa about 1.8 million years ago.
H. erectus is what biologists call a chronospecies, a species that changes through time. Homo ergaster is the name given to its earlier phase, which lived mainly in Africa; the later Homo erectus lived mostly in Eurasia.
Homo erectus stood upright and had a larger brain than several of its forebears, averaging between 780 to 1225 cc, considerably larger than H. habilis, the first of the genus Homo. Our modern human brain is about 1500 cc. The adult H. erectus was roughly 5 feet tall, with heavy, dense big bones, a large nose and a long, flat skull.
H. erectus was the first early human to venture out of Africa, and spread throughout the Old World. Its body was well adapted for running, with long legs and long Achilles tendons. While earlier hominids spent considerable time in trees as well as on the ground, H. erectus appears to have been fully terrestrial. It travelled for long distances, along the African and Eurasian coasts. The ice age had caused sea levels to drop, which may well have made it easy for groups to obtain food, as they moved along the coasts. Shell fish, and other aquatic food sources, rich in omega3, iron and other nutrients beneficial to brain development would have been plentiful. H. erectus reached as far as China in the West and Northern Europe in the East.
A recent 2004 study found that a variant of the MC1R gene, which is known to be important for darker skin color, was already present 1.2 million years ago.
This adaptation suggests that by this time our ancestors were well on the way to becoming hairless. The hair on our head remained, since it helped to combat overheating, by shielding the brain from the sun. The loss of body hair is associated with our propensity to sweat, which is an ideal way to regulate body temperature. This was important because, although being upright meant that our bodies were exposed to less direct sunlight, we needed to run long distances in order to hunt large game animals. Losing our body hair helped us lose heat by sweating, it enabled our diet to become rich in the proteins needed to fuel our growing brains, which, in turn, set the stage for more and more complex tasks, such as symbolic thought and language.
H. erectus were most likely the first to live in bands organized as hunter-gatherers, which would mean that they were able to coordinate their hunting behavior and most likely had some capacity for language. They cared for their injured relatives; and, as far back as 1.7 million years ago, created the most successful tool ever invented by any hominid: the bifacial hand axe. Known as Acheulean, these stone tools are evidence of our longest-running industry, lasting well over a million years, with examples found from southern Africa to northern Europe and from western Europe to the Indian sub-continent.
A large collection of shells, very similar to each other, dated about 500,000 years old appear to be H. erectus’ shell tools. Some of them have geometric engravings which are thought to have been made by H. erectus. These predate the earliest known engravings found at the Blombos Caves in South Africa by at least 300,000 years!
It is thought that H. erectus were the first to harness fire and cook food. Richard Wrangham, Catching Fire: How Cooking Made Us Human, feels this may well have occurred with the earlier Homo habilis and gave rise to H. erectus. He bases his theory on its larger brain and body, smaller gut, jaws and teeth and weaker jaw muscles – changes consistent with a more tender and energetically rich diet of cooked food.
Despite using these same unchanging Acheulean stone tools for thousands of years, H. erectus spread as far as China and Java. During this time, they shared the planet with other hominids: australopithecines and with two species of paranthropus all of whom were tool-using, upright walking, big brained hominids.
H. erectus lived nine times as long as our own species, and we don’t known why they eventually became extinct – they were still in China until about 300,000 years ago and possibly, quite a bit more recently, to about 143,000 years ago.