MadSci Network: Evolution

Re: Is there any new evidence of the earliest human life on earth?

Date: Thu Jun 11 08:57:27 1998
Posted By: Thomas M. Greiner, Assistant Professor of Anatomy / Physical Anthropology, New York Chiropractic College
Area of science: Evolution
ID: 895856562.Ev

When you ask for new evidence of the earliest human life it really depends upon what you mean by new and what you mean by human.

Humans, as we known them today, are classified as Homo sapiens. You might want to restrict your definition of human to that group. In that case, Homo sapiens seems to have appeared between 100,000 and 300,000 years ago. Much of the paleoanthropological investigations of early Homo sapiens focuses on where they originated. One theory states that modern humans evolved gradually, and simultaneously, in all parts of Africa, Europe and Asia from the ancestral species -- probably Homo erectus (but more about that later). This is known as the "Multiregional Theory." Other scientists think that Homo sapiens started out in Africa and eventually spread out over the world replacing the previous species. This is known as the "Out of Africa Theory." Both of these theories have strong evidence for and against them. This is one of the "hot" areas of human evolutionary research where you might expect to see a lot of new evidence.

If you accept a broader definition of what is "human" then you might also include other members of the genus Homo. Traditional interpretations state that the first member of the genus Homo was Homo habilis, which appeared in Africa about 2.5 million years ago. Somewhere between 1.5 and 2 million years ago Homo erectus evolved, and that was the species that spread to Europe and Asia. A few important new fossils have been found in past few years that bring new information to this scenario. Although most researchers still follow the tradition scheme, with various modifications, there has recently developed a new interpretation of the fossil evidence. This new interpretation sees many species of Homo, where just one (or two) were seen before. Now we hear about Homo ergaster, Homo rudolfensis, Homo heidelbergensis (the picture gives it a different name, but it really is Homo heidelbergensis), Homo erectus and Homo habilis (and a few other Homo species that I can't remember). Much of this new perspective follows the same line of thought as the Multiregional vs. Out of Africa theories for modern peoples. The tradition method had Homo erectus as the sole human species from 1.5 to 0.3 million years ago, which lived all over the Old World. The new scheme would divide Homo erectus into at least three different species -- with Homo erectus living only in Asia, Homo ergaster living in Africa (and being the ancestor of Homo sapiens) and Homo heidelbergensis living in North African and Europe. This is another "hot" area of research, where you can also expect to see a lot of new evidence. Within the last year, or so, a group of researchers in Spain found some human remains, which they are calling Homo antecessor . The validity, and relationships, of this new species still needs to be worked out, so expect to hear about it in the near future.

You might want to also include as human all members of the human family, or hominids. If you do that, then you would include the australopithecines and its related species. Traditionally four species are recognized: Australopithecus afarensis, Australopithecus africanus, Australopithecus boisei, and Australopithecus robustus (these last two are sometime placed in a separate genus as Paranthropus boisei and Paranthropus robustus). These hominids lived from about 4 to 2 million years ago, and some might have been around as recently as 1 million years ago. Investigations of these early hominids have produced both new interpretations (and therefore new species groupings) as well as new fossils. About three years ago researchers in Ethiopia found a very old hominid that they are now calling Ardipithecus ramidus, which seems to be a little more than 4 million years old. Just before that some researchers in Namibia found an even more ape-like creature (which probably isn't a hominid, but it may be close) that they call Otavipithecus namibiensis, which dates to about 9 million years.

Many researchers also focus on the early apes of the Miocene epoch, which lived from about 20 to about 5 million years ago. Sometime during this period the "first" hominid evolved. Although there have been many fossils that were thought to fit this first hominid status, none has yet been found that is completely satisfactory. You should probably expect to see exciting new evidence that addresses this area in the near future.

As you can see, the study of human evolution is an ever growing field. If you stand still too long, research will pass you by very quickly. Most of the new "evidence" comes from new ways of looking at the fossils, or even from new researchers with fresh ideas. For example, just a few years ago a researcher found a foot fossil in the drawer of a museum. This foot, which had never been fully studied before, is now giving important clues on the origin of upright, bipedal, locomotion. So, although new fossils are always important, some truly interesting discoveries can be made in a museum.

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