Many of you probably followed the discovery of a new species of Australopithecus, very likely a human ancestor, in 2010. The new species was called Australopithecus sediba. Two research articles published in Science magazine in April 2010 described a new species of Australopithecus dating from around 1.9 million years ago that casts new light on the evolution of the genus Homo. The discovery was so exciting that Science has a special feature, free to the public, on this discovery, that can be accessed here. The papers described bone fragments, including skull pieces from 2 specimens found in the Malapa cave, north of Johannesburg. The fossils have a mix of primitive features typical of australopithecines and more advanced characteristics typical of later humans. Thus, the team says, the new species may be the best candidate yet for the immediate ancestor of our genus, Homo. The claim is a big one and not all scientists agree with it, but the specimens are no doubt remarkable, look at this skull in the figure to you right! It is not too often that scientists come across 2 million year old specimens of potential human ancestors that are so well preserved.
On April 16 , 2011 (last Saturday) at a meeting of the American Association of Physical Anthropologists, more evidence from two new specimens of A. sediba ("sediba" means "wellspring" in the Sesotho language) has been presented that seems to indicate that the fossils should perhaps be classified our own genus, the genus Homo.
From ScienceNOW: In addition to the articulated partial skeletons of a youth and an older female unveiled last year in Science, the team members reported the discovery of bones of an 18-month-old infant and at least one other adult. This means they are getting a good look at Au. sediba’s development from infancy to old age. “It is going to be a remarkable record,” Berger [one of the main paleontologists in the study] said. “And we still haven’t found everything!”
The findings are exciting but the classification of the fossils is still controversial. The fossils show some surprisingly modern traits usually found only in members of our own genus. Two pelvises, in particular, are elongated and look quite Homo-like. Other modern traits include smaller teeth, short fingers, and an elongated thumb.
From Wired (and admire the amazing cranium in the photo):
It’s now clear that A. sediba shares more skeletal features with early Homo specimens than any other known Australopithecus species does, said Darryl de Ruiter of Texas A&M University in College Station. “We think A. sediba is a possible candidate ancestor for the genus Homo.” De Ruiter suspects that an isolated population of the hominid species Australopithecus africanus gradually evolved into A. sediba, resulting in a species characterized by an unusual mix of skeletal traits, some typical of Australopithecus in general and others of early Homo. That scenario, outlined in symposium presentations by De Ruiter and Lee Berger of the University of the Witwatersrand in Johannesburg, South Africa, remains controversial despite the new fossil discoveries. Ian Tattersall of the American Museum of Natural History in New York City endorsed A. sediba as a distinct species, probably closely related to A. africanus. “I wouldn’t classify it as the root of the Homo genus, though,” he commented.
As more fossils with transitional features continue to be be discovered, the picture of human evolution will become more and more clear; this of course, will have no bearing on the minds of creationists or intelligent designers who continue to deny that we indeed evolved from ape-like ancestors.
Physorg has a press release on this story:
Kristian J. Carlson discussed the size and shape of A. sediba's brain, showing that by synchrotron scanning of the interior brain case, they were able to determine the estimated capacity to be around 420 cubic centimeters. This led to a very small brain size and is the reason researchers first determined these new skeletal findings to be in the Australopithecus genus. However, they also discovered that the frontal lobe of this small brain contained organization more similar to that of humans, showing that contrary to what was previously thought, organization and brain size with human characteristics may not have been a simultaneous change.
The blog Afarensis comments on this too.
At issue is the question of whether A. sediba represents a late surviving population of A. africanus or whether A. sediba evolved into Homo.
I hate that expression.
Designer is a perfectly honourable profession, and many are intelligent.
"a new species of Australopithecus dating from around 1.9 million years ago"
an early human ancestor.. yeah, very remarkable!
I find some information here.
hope you like it :)
What is a gracile australopithecine?
All hominids, including the australopithecines, are bipedal, meaning that they walk on two legs, and are therefore members of the ancestral lineage leading to modern humans (we are the sole bipedal apes). However, our earliest ancestors probably retained some climbing ability, as evidenced by certain traits like curved finger bones, which may indicate that they are not yet fully committed to terrestrial bipedalism; they were, however, capable of it. They are called "gracile" because they generally have small (chimp-sized) bodies and brains. Their development is ape-like, rather than human-like - which is not surprising since human-like development is a derived (rather than primitive) trait - and have an ape-like degree of sexual dimorphism, suggesting ape-like social structure. Their faces are generally large and prognathic, reducing as you move through time towards a flatter more human-like condition. Similarly, their posterior teeth (molars) are big, generally reducing through time, while the tooth enamel thickness increases through time in the lineage. This indicates a transition from a more frugiverous and foliverous diet (a generalized ape condition) to one that is generally omnivorous (like us).
That was really great! Adriana thank you.
Interesting article. It concludes:
What we have learned in the last eight years is that our theories about early human ancestry are anything but set in stone. Any of these new fossil finds are poised to alter our understanding of early human ancestry. They have already extended the breadth of our knowledge both in geographic space and evolutionary time. Will they offer more? Only time will tell. But what is becoming increasingly clear is that we are dealing not with a family tree, but with a bush. Or as Darwin proposed - I think more appropriately - a coral, where the base of the coral is long dead, and only the tips live on.
When I look at the pictures of the remains, I get vertigo.
2 million years is one hundred thousand generations.
That's a lot of lifetimes, of caring, nurturing and learning.
Rather than start a new discussion, I decided to add to this existing thread because there is a lot of information and good comments here. Nicholas Wade, a science writer for the NYT, wrote a very nice article updating the A. sediba (also known as "Malapa fossils") story. These fossils are no doubt of great significance, although not everybody agrees with the conclusions of the FIVE articles published in the most recent issue of Science magazine. The authors of these articles conclude that they are on the main line of human evolution. Others are disputing that interpretation. These fossils are fantastic because they are unusually complete: two skulls, one complete right hand, a foot and a pelvis. They are extraordinarily well preserved because apparently these Australopithecenes fell into a cave 1.977 million years ago, and were quickly covered by sediments. The fossils display new combinations of human and ape-like features, for example the hand is like that of an ape, long fingers for climbing trees, but it also has a long thumb that in combination with the fingers could have been capable of a precision grip. Australopithecus sediba is just old enough to be the ancestor of Homo erectus, the first species that paleoanthropologists agree belonged to the human ancestry and which existed 1.9 million years ago. But others argue that there was simply not enough time for these to evolve into Homo erectus, after all, A. sediba has an ape-like brain. As usual, future discoveries will no doubt have an effect on the re-writing of the human tree.
An apelike creature with human features, whose fossil bones were discovered recently in a South African cave, is the most plausible known ancestor of archaic and modern humans, the scientists who discovered the fossils say.
The claim, if accepted, would radically redraw the present version of the human family tree, placing the new fossil species in the center. The new species, called Australopithecus sediba, would dislodge Homo habilis, the famous tool-making fossil found by Louis and Mary Leakey, as the immediate human ancestor.
Paleontologists agree that the new fossils, discovered by Lee Berger of the University of Witwatersrand in Johannesburg, are of great significance. But they do not necessarily agree with Dr. Berger’s contention, published Thursday in five articles in Science, that the fossils are on the main line of human evolution. As is common in the field of paleoanthropology, the discoverer of a new fossil is seeking to place it on the direct line of human descent, while others are resisting that interpretation.
Read the rest here
An here is a great article from Carl Zimmer on the five Science papers: "The verge of human"
The man is Lee Berger, a paleoanthropologist at the University of Witwatersrand in South Africa. He’s holding the skull of Australopithecus sediba, a 1.98 million year old relative of humans, otherwise known as a hominin. In April 2010 Berger and his colleagues first unveiled the fossil in the journal Science. As I wrote in Slate, Berger argued that A. sediba was the closest known cousin to our genus Homo. Hominins branched off from other apes about 7 million years ago, but aside from becoming bipedal, they were remarkably like other apes for about five million years. Among other things, they were short, had long arms, and had small brains. Berger and his colleagues saw in A. sediba what biologists often find in transitional forms–a mix of ancestral and newer traits. It has Homo-like hands, a projecting nose, and relatively long legs. It was intermediate in heigh between earlier hominins and the tall Homo. And it still had a small brain and long arms. (In August, Josh Fishman wrote a feature for National Geographic on A. sediba, complete with excellent reconstructions.)
It wasn’t just finding such a potentially significant fossil that would make you smile if you were Lee Berger. It’s how much stuff he and his colleagues have found. The skull that Berger holds would be enough to keep several scientists busy for years. But Berger and his team have much more. In fact, A. sediba is, in some ways, now even better represented than far more recent hominin relatives.
Today, Science has turned over much of this week’s issue to follow-up papers from Berger’s team, in which they share some of the goodies. Here, for example, is A. sediba’s hand. Before this specimen came to light, paleoanthropologists had much less to look at to study the origin of the human hand. The best specimen came from a 1.75 million year old hominin called Homo habilis. It got the name Homo in part because the fossils were found along with stone tools, which were considered a sign of a very human-like creature. Researchers also found bones from its hand–but only 13 fragments. In this picture of A. sediba’s hand, every bone is real. This is what paleoanthropologists dream about at night.
Read the rest here.