Hominid Species Time Line

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Homo ergaster

Homo ergaster lived from approximately 2 million to 1.5 million years ago in east Africa.  This species name was created in 1975 to accommodate African specimens formerly classified as Homo erectus. The name means “workman” in Greek, and derives from the stone tools associated with it.

Turkana or Noriokotome Boy—KNM-WT 15000

The spectacular find of a nearly full skeleton (above) belonged to a teen-age boy, estimated to be between 11 to 13 years of age, who, as variously estimated, lived 1.5, 1.8 or 1.9 million years ago near what is now Lake Turkana in east Africa.  This is the most complete skeleton on any early hominid species, and it has provided a wealth of information.

This individual, sometimes called Turkana Boy or Noriokotome Boy (after the site in which he was discovered) was five feet, four inches tall.  His body is remarkably modern looking.  As an adult, he would have stood slightly over 6 feet tall, with a brain capacity of @ 850 cc.  This individual was both powerfully and gracefully built, and perfectly adapted to swift, efficient bipedal locomotion.  The slim hips and un-flared rib cage suggest a hunter’s diet fairly rich in high-quality protein (N.B.:  older hominid species have flared rib cages to accommodate the large guts required to process rough plant food).  Oddly, while the muscle attachments on the bones suggest a highly developed muscular system, the spinal cord of this individual was significantly smaller than ours, indicating that it carried a smaller neural processing load.  One explanation for the small spinal cord is the probable absence of a fully developed speech system.

The Turkana boy is classified as Homo ergaster by some and Homo erectus by others.

KNM-ER 3733—Homo ergaster, discovered in 1975

Note the high forehead, which looks strikingly modern.  The brain size of this species ranged from 700-850 cc, and it is the first Homo species to have roughly the same body proportions as modern humans.  One male of this species was 6’3” tall.

References:

Homo ergaster on TalkOrigins.org