Courtesy Wikimedia Creative CommonsFossil bones from a creature named Australopithecus sediba show traits of both ape and human features that could shake up the field of human evolution. The fossils were found in South Africa in 2008 and according to lead researcher Lee R. Berger of the University of Witwatersrand in South Africa, analysis of the bones show it to be the most likely ancestor to modern humans.
The rare, complete fossil hand of A. sediba has a curvature like you’d expect in a tree-dwelling ape-creature but the thumb is long and the fingers slender, more human-like and could allow for possible tool use. The fragmental remains of a heel suggest an arched foot suitable for walking on the ground, and with an attachment for a large Achilles tendon. The pelvis is more bowl-shaped, broad, and human-like than that of the older Australopithecus afarensis known as Lucy.
"This is what evolutionary theory would predict, this mixture of Australopithecene and Homo," said Texas A&M paleoanthropologist Darryl J. DeRuiter. "It's strong confirmation of evolutionary theory."
A. sediba lived two million years ago, and represents a very fine example of a transitional fossil, but its brain is still small and more like that of a chimpanzee, and it’s that fact that may cause scientists to reconsider some of their earlier assumptions about how humans evolved.
The research appears in five separate reports in the current issue of Science.
Courtesy José-Manuel Benitos via Wikimedia CommonsFossil bones of two hominins
found in a cave in South Africa, could be those of a completely new species of human and fill in a gap in human ancestry. The remains, which were found within a yard of each other, are of an adult middle-aged female and juvenile male. Scientists speculate the two could even be a mother and its child, or at least members of the same tribe. Either way, they add valuable information to the very fragmentary record of human evolution.
Professor Lee Berger, lead researcher of the discovery, and a paleoanthropologist at the University of the Witwatersrand, says the remains are well preserved and between the two of them include a nearly complete skull, shoulder, arm, lower leg, and hand. The pelvis is well represented, too. The fossils were found in the Malapa cave not far from the Cradle of Humankind World Heritage Site near Johannesburg.
Named Australopithecus sediba, the new finds which are nearly two million years old, have characteristics common to both Homo (which includes us) and Australopithecus, early ape-like creatures, making it an important transitional fossil between the two genera. Photo link
“That period between 1.8 and just over two million years - is one of the most poorly represented in the entire early hominid fossil record. You're talking about a very small, very fragmentary record," said," lead scientist Lee Berger. "It's at the point where we transition from an ape that walks on two legs to, effectively, us.”
Berger is a professor of paleoanthropology at the University of the Witwatersrand in Johannesburg. First evidence of the find was actually found by his 9 year-old son, Matthew, who picked up a couple fossils bones, a collarbone and jawbone that had been discarded by miners. Further investigation led to the rest of the remains. Professor Berger had found the cave in 2008 using Google Earth.
Although clearly australopithecine in size and stature, and most closely similar to the species Australopithecus afarensis, the boy’s skull and jaw also contain features seen in the genus Homo, such as the facial structure (e.g. a slight bony chin), and the shape and size of the premolars and molars. The two creatures upper limbs were overly long, again a trait of Australopithecus, and means they were more-than-likely arboreal, and able to easily climb trees to seek refuge and food. But their pelvic structures share features found in the hips of the Homo genus, leaning toward more efficiency in walking or running. This means A. sediba fills in some of the gap between Australopithecus afarensis and Homo erectus. Professor Berger’s study appears in the journal Science.
Berger suspects the two A. sediba had been swept into the cave by a flash flood or some such disaster and buried fairly quickly. The dig site produced the remains of 25 other animals such as a horse, saber-toothed cat, wild dogs, and antelope. None of the remains appear to have been scavenged Fossils from two other hominid individuals were also found but have not yet studied.
Courtesy TmkeeseyMove over Lucy, there is a new hominid in town. Her name is Ardi. One could say Ardipithecus ramidus to be formal. She is a 4.4 million year old ancestor of ours and nearly a million years older than Lucy (Australopithecus afarensis). She is by far the most complete of all the older hominids. Researchers have recovered feet, a leg and pelvis, hands and lower arm, along with the majority of a skull and its teeth. As an added bonus, parts of nearly three dozen more specimens were recovered during the work in the Western Afar Rift of northeastern Ethiopia. This is the same region that gave us Lucy and some early Homo species.
Ardi and her kin walked upright, although their gait was debatably awkward. She retained an opposable toe which could still be used to grasp tree branches, but the remainder of the foot was built for the ground. Like later hominids, the teeth reveal a modern structure and lack enlarged canines. Her pelvis is a mosaic between chimps and Lucy. The Ilium developed short and broad more like a human, while the lower pelvis remains similar to a chimp. Ardi’s skull shows that her brain was still the size of a chimp, being smaller than Lucy’s. Its shape, however was more hominid and had begun evolve more advanced functions.
Unlike Lucy in her savannah habitat, Ardi roamed lush but temperate woodlands. More than 150,000 plant and animal fossils were recovered from the sites. Included are 20 new species of small mammals along with monkeys, antelope, elephants, and multitudes of birds. This was a much different environment than that of the savannah. Theories of the development of bipedalism on the open grasslands will be challenged now because of Ardi and her habitat.
This isn’t a recent find. The original excavations of the search teams started in 1992. But years of field work followed by more than a decade of lab time have really unearthed a mass of data about this time and place in history. 47 diverse researchers from all over the world have included excerpts of their findings about Ardi and her environment. The October 2009 special issue of the publication Science details the discovery and ongoing analysis of this latest find in the continuing quest to uncover the origins of man. With debate well underway, I’m positive we’ll all continue to learn more about our past.
more on Hominid evolution
Early human ancestors, called Australopithecines (AW-stroh-la-PITH-eh-scenes), had short legs. Scientists have long believed this was a hold-over from even earlier species which had lived in trees. But now biologist David Carrier of the University of Utah argues the short legs were used to help them fight.
Short legs give a body a lower center of gravity, and makes it harder to push over. Living apes with short legs, like gorillas, tend to be more aggressive, while long-legged apes, like gibbons, are more docile.
Of course, humans don’t have such short legs anymore. Herman Potzner of Washington University in St. Louis proposes later human species evolved long legs to save energy. His studies of various animals show that that longer a creature’s legs, the less energy they use. Around 2 million years ago, something happened in human evolution that made the fighting advantage of short legs less important than the energy savings of long legs.
The fossil including an entire skull, torso, shoulder blade and various limbs was discovered at Dikaka, some 400 kms northeast of the capital Addis Ababa near the Awash river in the Rift Valley.
"The finding is the most complete hominid skeleton ever found in the world," Zeresenay Alemseged, head of the Paleoanthropological Research Team, told a news conference. Reuters
The fossil has been named "Selam", which means peace in Ethiopia's official Amharic language.
"The Dikika girl stands as one of the major discoveries in the history of palaeoanthropology," research team leader Zeresenay Alemseged said, citing the remarkably well-preserved condition of the bones, the geological age and completeness of the specimen.Cosmos Magazine
The following is the abstract of the original article describing the baby, which was authored by Zeresenay Alemseged, Fred Spoor, William H. Kimbel, René Bobe, Denis Geraads, Denné Reed and Jonathan G. Wynn, and appeared in Nature on September 20, 2006.
"Understanding changes in ontogenetic development is central to the study of human evolution. With the exception of Neanderthals, the growth patterns of fossil hominins have not been studied comprehensively because the fossil record currently lacks specimens that document both cranial and postcranial development at young ontogenetic stages. Here we describe a well-preserved 3.3-million-year-old juvenile partial skeleton of Australopithecus afarensis discovered in the Dikika research area of Ethiopia. The skull of the approximately three-year-old presumed female shows that most features diagnostic of the species are evident even at this early stage of development. The find includes many previously unknown skeletal elements from the Pliocene hominin record, including a hyoid bone that has a typical African ape morphology. The foot and other evidence from the lower limb provide clear evidence for bipedal locomotion, but the gorilla-like scapula and long and curved manual phalanges raise new questions about the importance of arboreal behaviour in the A. afarensis locomotor repertoire."
Additional reading: BBC News