New Fossil Finds Challenge Long Held Theories Of Evolution
Sep 16, 2007 by Brad Horowitz
Previous to the discovery of two hominid fossils that were recently discovered in Kenya the "hominid Homo habilis" was almost universally thought to have evolved into the more advanced "Homo erectus" which then evolved into us.
It now appears however that the "habilis" and "erectus" are sister species that overlapped for around 500,000 years during which time "Homo habilis" and "Homo erectus" must have co-existed in the Turkana basin area which is a region of East Africa where the fossils were unearthed.
"Their co-existence makes it unlikely that "Homo erectus" evolved from "Homo habilis". Instead, both species must have had their origins between 2 and 3 million years ago, a time from which few human fossils are known. The fact that they stayed separate as individual species for a long time suggests that they had their own ecological niche, thus avoiding direct competition", explained Meave Leakey who is one of the lead authors of a paper just published in "Nature".
A second lead author, Fred Spoor, another added, "The second fossil found in the same region of northern Kenya is an exquisitely preserved skull of Homo erectus, dated to about 1.55 million years ago. What is truly striking about this fossil is its size. It is the smallest Homo erectus found thus far anywhere in the world".
The jaw bone has been attributed to "Homo habilis" because of its distinctive primitive dental characteristics and was dated to around 1.44 million years ago and is the youngest specimen of this species ever found.
The skull however was assigned to the species "Homo erectus" despite being similar in size to the habilis skull.
Most other erectus skulls that have been found are considerably larger but this one displayed the typical features of erectus such as a gentle ridge called a "keel" which runs over the top of the jaw joint.
If "Homo erectus" had evolved from "habilis" and stayed within the same location then both of them would have been in direct competition for the same resources and eventually one of them would have out-competed the other.
"The fact that they stayed separate as individual species for such a long time suggests that they had their own distinct ecological niches, thus avoiding direct competition," Professor Leakey explained.
Professor Chris Stringer who is the head of human origins at London's Natural History Museum, said, "Both were apparently stone tool makers but one possibility is that the larger and perhaps more mobile erectus species was an active hunter while habilis scavenged or caught small prey".
The broken upper jawbone and the intact skull from humanlike creatures or hominids as they are known are described in "Nature" and both offer major challenges to the presently long held views of human evolution.
"Nature" is an International journal of science and can be found at http://www.nature.com/