Last Thursday, scientists published a series of articles providing a detailed analysis of a relatively new alleged human ancestor—Australopithecus sediba. The pair of fairly complete skeletons from an adult female and juvenile male was subjected to a comprehensive analysis of the skull/brain, pelvis, hand, and foot/ankle to enable scientists to understand where this hominid fits in human evolutionary history. Rather than providing clues to human ancestry (as the news headlines claim), Australopithecus sediba makes the human evolutionary story much more complicated. Indeed, characteristics of Au. sediba support the creationist case of created kinds and the idea that the Australopithecines represent an extinct kind of arboreal (tree-dwelling) ape.
As frequently occurs with newly discovered hominid fossils, scientists and especially the news media have promoted the find as providing clear evidence of how humans evolved. Au. sediba is the latest example of a “missing link.” Evolutionists do not like the term “missing link” and prefer to describe such fossils as “intermediate” or “transitional.” Evolutionist Carl Zimmer wrote the following:
The term “missing link” serves no good purpose today. Creationists use it to try to cast doubt on the reality of evolution whenever a new hominid fossil is discovered. They point out the features of the fossil that aren’t shared by humans or living apes, and claim that those traits are proof that the hominid couldn’t have bridged the two groups. These arguments hardly call human evolution into doubt. The only lessen that should be drawn from them is that the term “missing link” should be retired for good.1
Each hominid fossil would be expected to have certain ape-like and human-like traits and perhaps even unique traits. Zimmer does have a point—selectively pointing out traits that aren’t shared by humans or living apes does not prove that a fossil hominid could not have bridged the two groups. A better conclusion may be that the fossil hominid is an extinct kind of ape and is related neither to humans nor living apes. Such appears to be the case for Au. sediba.
Details on the fossil
Researchers made an endocast of the inside of the skull, which allowed them to determine the cranial capacity and model the shape of the brain. From this, they found that the cranial capacity was 420 cubic centimeters, which compares with other Australopithecines and is close to that of chimpanzees. It is also less than half the size of Homo erectus specimens. Even though the brain of Au. sediba is small, scientists suggest that certain aspects of the front of the brain are shaped more like a human than those of other Australopithecines. While interesting, this type of global brain architecture does little to demonstrate anything about intelligence or behavior. The number and type of synaptic connections between neurons of the brain underlie cognition and behavior, and these are not revealed by overall brain shape.
Berger and his team found most of the right hand of one of the fossil specimens. Only the fingertips and a few wrist bones were missing. This allowed investigators to get a good picture of hand anatomy. Interestingly, the hand was described as a “mosaic” even in the title of the article since it had features of Australopithecines and humans.3 The hand has a strong flexor apparatus, and the fingers are curved suggesting arboreal (tree-dwelling) locomotion, which has been suggested previously for the Australopithecines.
This only shows that the thumb is long and unique; it is not human-like at all.
The most surprising feature of the hand is the very long thumb. Chimpanzees, gorillas, and Australopithecines tend to have short thumbs that appear exaggeratedly small combined with long fingers. In the case of Au. sediba, the thumb is quite long compared to the fingers and in fact has a larger thumb to finger length ratio than humans. The authors suggest that the long thumb is Homo-like and in fact it is the thumb that provides nearly all the human-like characteristics of the hand. The authors suggest that the long thumb would allow precise gripping and perhaps stone tool production. However, with such a long thumb, the grasping would not be entirely human like. To reiterate, they conclude that a large thumb-to-finger length ratio makes the hand human-like, even though the Au. sediba thumb is so long that the ratio falls well outside the range of humans. In reality, this only shows that the thumb is long and unique; it is not human-like at all. Exactly how this creature used such a long thumb is a mystery.
Berger’s team used partial pelvis fragments to frame a full model of the pelvis of Au. sediba.4 The reconstructed model pelvis indicates a mixture of Australopithecine and human characteristics. The Au. sediba pelvis is bowl-shaped, and the orientation of the iliac blades is more similar to humans than that of chimpanzees. Since Au. sediba has small cranial capacity and a large opening through the pelvis, delivery of a baby for this creature would not pose the difficulty that it does for humans. In order for a human baby to pass through the pelvis, the head must turn and the mother’s pubic symphysis (the joint where the pubic bones meet) must be stretched to allow the baby through.
While the pelvis has some features that are consistent with bipedal locomotion, it is important to point out that a tree-dwelling creature would require a more upright posture than a creature that knuckle walks. For example, orangutans, which are arboreal, do not knuckle walk and have certain features of the lower limbs that are more similar to humans than to chimpanzees. Thus, we should not be surprised by some traits consistent with upright posture in an otherwise arboreal creature.
The foot and ankle
Like the hand, the foot and ankle of Au. sediba have both “primitive” and “advanced” features and are thus properly described as a mosaic.5 With so many human-like characteristics in Au. sediba, the foot is particularly unexpected. This is because older types of Australopithecines such as Au. afarensis (Lucy’s type) have a more human-like foot than Au. sediba which is more “primitive,” like that of a chimpanzee. This means that if the evolutionary progression goes from Au. afarensis to Au. sediba and then on to modern humans, the foot must evolve to a more advance state in Lucy and then revert to a primitive state in Au. sediba before returning to an advanced state again.
Summary of Au. sediba characteristics
Au. sediba has more similarities to humans than any other types of Australopithecines. Still, Berger classified it as an Australopithecine. Taken together, it is a small-brained creature with primarily tree dwelling locomotion and the capacity for some type of bipedal locomotion. It has an exceptionally long thumb that could possibly play a role in grasping branches. It also has a mixture of primitive and advanced characteristics in the foot with aspects of the foot more chimp-like than older types of Australopithecines.
The articles from this new series in Science focused on the most human-like traits of Au. sediba. There are a number of characteristics discussed previously that are clearly quite ape-like, not the least of which is the long arms and sloped face.6 Additionally, a number of features of the shoulder are consistent with arboreal locomotion and thus more apelike.
Back to the future
Perhaps the factor that raises the most questions regarding the role of Au. sediba in human evolution is the date.7 Coming in at just under 2 million years according to radiometric U-Pb and paleomagnetic dating, Au. sediba is actually younger than other hominids including Homo rudolfensis, Homo habilis and some Homo erectus specimens. This raises serious questions about whether Au. sediba belongs in the direct line of human ancestry at all. Previously, scientists have debated the role of H. habilis and H. ergaster, in part because these overlap for 200,000–300,000 years according to evolutionist dating. How is Au. sediba supposed to be a human ancestor when the dating is overlapping both of these hominids which had significantly larger brains? Rather than bringing clarity to human origins, Au. sediba raises more questions than it answers. The problem is that evolutionists claim fossils with greater similarity to modern humans are older. This, combined with the foot more chimp-like than Lucy (with a much older date) means that evolution would go in reverse for a time before moving forward.
Creationists understand the diversity of life to represent numerous created kinds with variation within the kind. God directly created the various kinds of living things, and He made them with a range of characteristics and the ability to adapt. For example, wolves, coyotes, and the different dog breeds are all part of the same dog kind; while donkeys, zebras, and horses are part of the horse kind. Since this is what we observe when we examine living organisms, we should expect the same thing in the fossil record. Therefore, the various Australopithecines (afarensis, anamensis, africanus, gahri, and sediba) give us a picture of what this kind of extinct ape was like and the range of variation that existed. Since there is such a range of variation, it should not surprise us that one type would appear to be more human like than others. Creationists make a mistake when they try to make a fossil hominid into a chimpanzee or into a human when it may really be in its own separate group.
Evolutionists acknowledge the clustering of the fossil hominids into groups. When visiting the new human origins exhibit at the Smithsonian Museum of Natural History, I was struck by the grouping of the hominid fossils.8 They showed the Ardipithecus group, the Australopithecus group, the Paranthropus group, and the Homo group as separate clusters of branches on a human ancestor tree. It was easy to see how the individuals that comprise each group could represent the variation within the kind with clear boundaries separating each kind. As more and more hominid fossils have been found, scientists can get a more complete picture of the range of variation within each kind. In the process, the clarity of which ones comprise the supposed human lineage evaporates (compare Figures 1 and 2). The only thing that connects the different kinds is the line that evolutionists draw. Unfortunately for them, with each new hominid fossil, it is becoming harder and harder to figure out which lines to draw for human ancestry.
In spite of certain human-like characteristics—many of which are consistent with tree dwelling—the overwhelming evidence is that Au. sediba was a type of Australopithecine and thus an extinct ape rather than a human ancestor.
received his Ph.D. in neuroscience from Case Western Reserve University. He is currently the chair of the Department of Biology & Chemistry and the director of the Center for Creation Studies at Liberty University. He is the author of Unravelng the Origins Controversy. Dr. DeWitt has written a number of articles on the topic of human origins.