Map of East Africa showing tectonic plates

USGS, 5 May 1999

New fossil finds shed light on earliest human ancestors

By Jim Genova, People's Weekly World, 2 September 1995, pg. 15

Recent fossil discoveries in Kenya have sharpened debate on the earliest origins of humans and has thrown open the question of how long hominids (as all human species are known) have walked upright.

Leg and arm bones of about 21 individuals and a few jaw bones were found near Lake Turkana last month and have been dated to between 3.9 and 4.4 million years ago. They are said to belong to a new species called Australopithecus Anamensis, and show distinct traits indicating that they walked upright - a finding that pushes~ the earliest known date for hominid bipedalism back about half a million years.

The jaw bones show ape-like characteristics - placement of the teeth, small ear openings in the skull. But the teeth also show characteristics which are unique to humans - namely, the tooth enamel is much thicker than apes, a feature common to hominids.

According to the international team of paleontologists working on the siite, the arm and leg bones clearly belong to a species of upright walkers. The upper part of the shin bone is shaped so as to bear much more weight than the four-legged apes, thus allowing the hominid to walk erect. This feature was crucial for allowing later increases in brain size. With upright walking, humans were able to free more air and blood to flow to the brain, allowing it to grow. The body was better able to cool itself and the hands were freed to be used creating tools and processing foot.

Since these finds belong to a species much older than that of the fameous Lucy fossils discovered in the 1970s, many paleontologists and anthropologists are faced with a radical rethinking of previous assumptions on human lineage. It now seems, according to Dr. Meave Leakey of the National Museums of Kenya and wife of noted fossil hunter Dr. Richard Leakey, that there were a number of hominid species coexisting during man's formative years. Several of the earliest hominids may simply have died out and may have no relation to Homo Sapiens Sapiens, the sole surviving hominid species.

This has opened a new field of inquiry into how the earliest hominids, if at all, interacted with one another - Were they bitter rivals, with one species killing off another? Did they cooperate with one another? Or, did they keep their distance and occupy different and unrelated niches in the food chain of East Africa?

These latest finds may help in the understanding of man's relation to the apes and to other surviving species. If paleontologists and anthropologists can piece together the life styles of the earliest hominids, it may aid in the understanding of human nature, instinct and climatic and genetic traits which eventually led to the rapid increase in human brain size and to the evolution of human culture.

UP THERE IS A MAP OF EAST AFRICA

Map of East Africa showing some of the historically active volcanoes (red triangles) and the Afar Triangle (shaded, center)—a so-called triple junction (or triple point), where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone.