A New Type of Human
Finding dinner on the African savannah was no easy task for our early relatives. Armed only with simple stone tools, hominids butchered animals like antelopes while fending off scavengers such as hyenas, jackals and vultures.
The hominids shown here are members of the species Homo ergaster, which first appeared on the scene about two million years ago. Tall and slender, with long legs and larger brains than most of their predecessors, these hominids are very early precursors of modern humans, but their overall body form is very similar to ours.
Focus On: Homo ergaster
When: 1.9 to 1.4 million years ago
Brain Size: around 850 cubic centimeters, around twice the brain size of a chimpanzee but about two-thirds that of a modern human
Diet: probably mostly plants with some meat
Average Adult Height:
females: 1.6 meters (5 feet, 3 inches)
males: 1.8 meters (5 feet, 11 inches)
Average Adult Weight:
females: 56 kg (123 pounds)
males: 68 kg (150 pounds)
What Did Early Hominids Eat?
By two million years ago, our ancient relatives had added meat to their diet. How do we know? Animal bones from around this time have been found with cut marks made by stone tools, a clear indication that early hominids cut up animal carcasses to eat the meat. Firm evidence for the domestication of fire is only occasional at best before 400,000 years ago, so early hominids such as Homo ergaster probably ate their meat raw.
Gorillas and many other modern primates live in groups of more than 20. Scientists are not sure exactly how large early hominid groups were, or how these groups were organized. But there is no question that these ancient primates, too, were social animals. An adult male and female Homo ergaster are shown as a pair in the diorama, but the scene is not intended to suggest a nuclear family.
Tall and Slender
Homo ergaster's tall body, long legs and relatively short arms look remarkably similar to those of modern humans. What genetic changes caused this sudden transformation?
Researchers can only guess--a huge variety of genes affect skeletal growth. But geneticists have learned that even small changes in DNA can have a big impact. For example, "regulatory" genes control the timing and expression of other genes. Altering one of them can have cascading effects throughout an individual's development. In this way, a change in a single gene might have reshaped Homo ergaster.
Some modern human peoples, such as the Samburu of northern Kenya, tend to have especially long, slender limbs, a feature that allows the body to cool efficiently. A similar trait may have helped Homo ergaster survive in the hot, dry climate of eastern Africa.