August 9, 2007
Bones May Change Ideas on Evolution
By Wendy Leonard Deseret Morning News
Early human fossils found and researched by a group containing two Utah scholars may challenge popular notions of how humanity evolved.
"For most of geologic time there was more than one type of early man running around, and this documents it pretty well for this interval of 1.4 (million) to 1.9 million years ago," said Frank Brown, dean of the College of Mines and Earth Sciences at the University of Utah. "The real difference is that people used to think that Homo habilis was ancestral to Homo erectus."
Brown and U. doctoral student Patrick Gathogo, along with seven other researchers, helped date volcanic ash deposits to determine the ages of two early human fossils discovered in Kenya seven years ago.
The first fossil is a 1.44 million-year-old partial jawbone of Homo habilis, the earliest known species of our genus, Homo. The discovery demonstrates that the species survived longer than previously thought by researchers. It shows that for a half-million years, two species of early humans lived side by side in Africa, contrary to the old view that one species, Homo erectus, evolved from the the other.
"As you go through time, in general there was more than one hominid. Yet today Homo is represented by only a single species: us," Brown said from Nairobi, Kenya, earlier this week. He is expected to return to Utah later this month.
The other fossil is a 1.55 million-year-old skull of Homo erectus, which is much smaller than a previously discovered specimen, making it the smallest Homo erectus found anywhere in the world, according to a study published in today's issue of the journal Nature. It is now a question of whether males and females in the same species were different sizes, much like prehistoric gorilla species.
Researchers believe the find indicates the species was much less like modern-day humans, Homo sapiens, than previously believed. According to the article, the variation in Homo erectus skull sizes also suggests males in this species of early human may have had multiple mates, from either species at the time, which could help explain how the two species meshed into current human form.
Brown and Gathogo contributed to the study by determining the order of volcanic ash layers above and below the fossils, allowing scientists to determine the ages of the fossils using a sediment dating process. Dating the mineral feldspar in the ash layers provided numerical age estimates for the fossils.
"We understand well enough how the layers of sedimentary rock that preserved these fossils relate with ancient environments," Gathogo said.
The fossils were discovered by the Koobi Fora Research Project, an international group of scientists directed by mother-daughter team Meave and Louise Leakey, in 2000. It was during fieldwork in the Ileret region, east of Lake Turkana, in northern Kenya, where more than 16,000 fossil specimens have been collected, including 350 hominid bones.
The recent discovery, as stated in the journal article co- authored by the Leakeys, Brown, Gathogo and others, sheds light on the emergence and early evolution of humans as we know them, a topic that has been studied for centuries and with new research will continue to be of interest to researchers.
Gathogo said that he and others will continue to search for more fossil sites in order to learn more about human evolution.
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