EARLY HOMOS: HOMO HABILIS, HOMO RUDOLFENSIS AND HOMO ERGASTER
Homo habilis Members of the genus homo have larger brains and a smaller, ape-like faces. What distinguished them from their predecessors was is ability to make stone tools. Homo erectus was the first species to expand into Asia and Europe. Homo is Latin for "human." [Sources: Homo erectus, National Geographic, May, 1997; Homo erectus, Rick Gore, National Geographic, July 1997]
Claims to the oldest Homo fossils include a 2.4-million-year- old mandible from Uraha, Malawi, a 2.4-million-year-old skull fragment from Lake Baringo, Kenya and a 2.3-million-year-old upper jawbone from Hadar, Ethiopia. For the most part though the period between two million and three million years ago there is little data and few fossils.
Homo species had longer bodies than the short and stocky Australopithecus species. Since about 1.8 years hominids have been within the size range of modern humans. Male and females size differences characteristic of Australopithecus species decreased.
Websites and Resources: Modern Human Origins modernhumanorigins.com ; Talk Origins Index talkorigins.org/origins ; Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; Time Space Chart Hominid Fossils Pictures msu.edu/~heslips ; Smithsonian Human Origins Program humanorigins.si.edu ; Wikipedia article on Human Evolution Wikipedia ; Becoming Human University of Arizona site becominghuman.org ; Human Evolution Images evolution-textbook.org ;Hominid Species talkorigins.org ; Institute of Human Origins iho.asu.edu ; Paleoanthropology Link talkorigins.org ; Britannica Human Evolution britannica.com/EBchecked/topic/275670/human-evolution ;Modern Human Origins modernhumanorigins.com ; Human Evolution handprint.com ; Paleoanthropology and Evolution Links unipv.it/webbio/dfpaleoa ;National Geographic Atlas of the Human Journey genographic.nationalgeographic.com/genographic/atlas ; Yale Peabody Museum peabody.yale.edu/exhibits/fossils ; Humin Origins Washington State University wsu.edu/gened/learn-modules ; Book: The Human Evolution Source Book
Development of Australopithecus Into Homo
scientists have different theories about which hominids evolved into more developed species and which lead to evolutionary dead ends. Some scientists believed that the Homo genus evolved from Australopithecus afarensis . Others believe it developed from Australopithecus afarensis . Bosei and robustus are believed to be evolutionary dead ends because they lived at the same time as Homo species. The various theories are difficult to prove.
The brain volume of Australopithecus species ranged between 400 and 500 cubic centimeters while the brain volume of early Homo species was between 600 and 750 cubic centimeters.
There is some debate as to whether the Homo genus evolved in East Africa or evolved in southern Africa and migrated north. Proponents of the southern Africa theory believe that the earliest Homo species evolved from A. africanus (Taung Child) and base their argument on the facts that arrangement of her teeth and brain size are similar to that of Homo habilis (the earliest Homo species), their fingers are humanlike and their brains were of similar size to Homo habilis .
Homo habilis , meaning "handy man," was dramatically different from his predecessors. Homo habilis appeared around the same time as the first stone tools. Some scientists suggest the transformation from Australopithecus to Homo habilis was brought about by climatic changes.
Geologic Age 1.4 million to 2.5 million years. Very few H. habalis remains have been found, but scientists speculate he survived about a half a million years. He lived at same time as Australopithecus boisei. Linkage to Modern Man: Seen as direct ancestor. Not clear what Australopithecus species he evolved from.
Discovery Sites: Eastern and southern Africa. Discovered at Olduvai Gorge, Tanzania in 1959 by Mary Leakey and found near Lake Turkana at Koobi Fara, Kenya by B. Ngeneo and the Sterkfontein and Swartkrans in South Africa. Leakeys. The Lake Turkana remains are housed at National Museum of Kenya in Nairobi.
Homo habilis Body Features and Size
Homo Habilis tooth Size: Small compared to modern humans. males: 4 feet 4 inches; females: 3 feet 10 inches, 71 pounds. Skull Features: Primitive face, back teeth narrower. Larger brain and smaller human-like jaws and teeth than those found on Australopithecus species. Body Features: More similar to modern man.
Brain Size: 630 cubic centimeters, significantly larger than predecessors. Although half the size of modern man's brain, it's brain was large relative to body size and almost the same relative size as the brain of modern man. There was a pronounced bulge in the area of the brain associated with speech. Scientists say it probably didn't speak because it's vocal chords were not developed enough. A human brain is about 1,350 cubic centimeters. A chimpanzee’s brain is 390 cubic centimeters.
A February 2009 article in Science announced the discovery of 1.53-million -year-old footprints found at Ileret, Kenya. The footprints, likely made by early Homo habilis or Homo ergaster , were heralded as the earliest evidence of modern upright walking. The large toe was parallel to the other toes, indicating an upright posture. The 3.6-million-year-old prints found in Tanzania and attributed to an Australopithecus species indicated an upright posture but had a shallower arch and an apelike divergent toe. The discovery was announced by a team led by Matthew Bennet of Bournemouth University in Britain.
Homo habilis Tools
Homo Habilis skulls Homo habilis appeared around the same time as the first stone tools, which included cobbles and choppers made from lava. Some of the tools were made of materials not found in the area where the tools were found. This implies the materials were carried to the area where they were found from a distant site, which in turn implies the transportation of goods of even trade.
Homo habilis consisted mostly fist-size hammerstones and small, sharp flakes. Scientists believe that Homo habilis and his tools were too small too hunt large prey. The tools, they theorize, were used mainly to fight off competing scavengers for the large carnivores such as lions and cut the hides and break open the bones of their scavenged meals. Homo habilis deliberately hammered and shaped rocks into these tools.
Homo Habilis and Homo Erectus
In an August 2007 article in Nature, Maeve Leakey of the Koobi Fora Research Project announced her team had found an upper jawbone of a Homo habilis east of Lake Turkana in eastern Kenya dated to 1.44 million years ago, making it much more recent than other fossils from the species.
Homo ergaster It had previously been theorized that Homo habilis and Homo erectus lived at different times and Homo erectus evolved from Homo habilis . The discovery by Leakey’s team however seems to counter this finding, suggesting that the two hominids lived together for around a half million years, which in turn makes it unlikely that Homo erectus evolved from Homo habilis .The finding does not challenge the theory that Homo erectus are the direct ancestors of modern humans but it does call into question whether Homo habilis was.
Scientists now theorize that Homo habilis and Homo erectus had a common ancestor that lived between two million and three million years ago, a period in which there is little data and few fossils. Leakey told the New York Times that the finding of her group suggests Homo habilis and Homo erectus “had their own ecological niche thus avoiding direct competition...Their coexistence makes its unlikely that Homo erectus evolved from Homo habilis.” Fred Spoor, a Leakey colleague from the University College of London, said the finding contradicts previous theories that present human evolution “as one strong single line from early hominids to us” and supports the revised interpretation of “a lot of bushiness and experimentation in the fossil record.”
The 1.44 million-year-old Homo habilis fossils were found several years before but extra care was taken identifying the species and dating the fossils, which was done from volcanic ash deposits, to make sure they got it right since the implications of the finding are so dramatic.
Homo rudolfensis and Homo ergaster
homo ergaster Nariokotome Boy Homo rudolfensis , is a hominid species that lived between 2.5 million and 1.9 million years ago. Little is know about this hominid which sprung up about a half million years before Homo habilis died out. Many scientists regard Homo rudolfensis as a member of the Homo habilis species. If not it is the earliest known homo species. Skull Features: Long, broad face with flatter browridges and a larger, rounder braincase that Homo habilis . Discovery Sites: Eastern Africa. Omo, Ethiopia; Koobi Fora at Lake Turkana, Kenya; Uraha, Lake Malawi.
Homo ergaster is a hominid species that lived between 1.8 million and 1.4 million years ago. Many scientists regard Homo ergaster as a member of the Homo erectus species. Skull Features: smaller jaws and a more projecting nose than earlier Homos. Body Features: Arm and leg proportions more similar to modern man. Discovery Site: Koobi Fora at Lake Turkana, Kenya.
"Turkana Boy" is a nearly complete skeleton and skull from a 12-year-old boy that lived 1.54 million years ago and was discovered in 1984 near the shores of Lake Turkana not far from Nariokotome, Kenya. Some scientists think he is Homo erectus . Others regard him as distinctive enough to be regarded as a separate species— homo ergaster . Turkana Boy was about 5-foot, 3-inches tall when he died and probably would have reached a height of about six feet if he reached maturity. Turkana boy is the most complete skeleton of a hominid more than a million years old.
See 1.7-Million-Year-Old Hominid Fossils in Georgia
Image Sources: Wikimedia Commons
Text Sources: Mostly from National Geographic articles. I’ve gone through them all since around 1963 or so. Also the New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Times of London, Natural History magazine, Archaeology magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Lonely Planet Guides, World Religions edited by Geoffrey Parrinder (Facts on File Publications, New York); History of Warfare by John Keegan (Vintage Books); History of Art by H.W. Janson (Prentice Hall, Englewood Cliffs, N.J.), Compton’s Encyclopedia and various books and other publications.
© 2009 Jeffrey Hays
Last updated March 2011