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Saturday, December 20, 2014

Australopithecus sediba: An Extinct Ape

Posted by jlwile on April 17, 2010

On April 8th, Scientific American’s website had a story entitled “Spectacular South African Skeletons Reveal New Species from Murky Period of Human Evolution.” In that post, the author said:

Scientists working in South Africa have unveiled fossils of a human species new to science that they say could be the direct ancestor of our genus, Homo.

So those who discovered the fossil think that it could be a direct ancestor of genus that contains modern humans. Do the data support this bold claim? Not at all. In fact, based on the actual fossils that have been published,1 A. sediba looks like nothing but a specialized form of extinct ape.

First, you need to understand the nature of these fossils. They seem to come from two individuals. One is assumed to be an adult female (and is called MH2), and the other is assumed to be a juvenile male (and is called MH1). To get an idea of what few remains we have from these two individuals, you should click on the link below, where the actual fossil remains are laid over sketches of what complete skeletons would look like.

Illustration of the actual fossils

So from the assumed juvenile male, we have a fairly complete skull, one fairly complete humerus, one fairly complete tibia, one fairly complete clavicle, and assorted bits from the spine, pelvic girdle, ribcage, femur, and feet. From the assumed adult female, we have a fairly complete humerus, a fairly complete radius, a fairly complete ulna, a fairly complete scapula, and assorted bits from the jaw, clavicle, spine, ribcage, pelvic girdle, femur, knee, fibula, and feet. That’s not much to go on.

However, you’ve got to go with what you have, so now that we know what fossils we’ve got, what do they tell us? Well, let’s start with cranial capacity. We can only get that from the juvenile, so automatically we must be worried about how well-developed the juvenile is. However, the authors think the juvenile’s cranium is probably 95% developed, and the estimated cranial capacity is 420-450 cc, which fits nicely into the australopithecine range of 350-600 cc.2

Next, let’s look at the arms. The arms are very long, exactly what you would expect of an australopithecine. One of the defining characteristics of primates is the size of the radius or ulna relative to the humerus, which is called the brachial index. Since the adult female has one set of mostly complete arm bones, the brachial index is easy to calculate. It ends up being just over 100, which is typical of an orangutan, very close to the 78-91 range of australopithecines, and very far from the 65-83 range of humans.3

Next, let’s look at the size. The estimated size of the adult is 1.3 meters, which is right in the australopithecine range of 1.2 – 1.5 meters4 and well outside the typical range found in humans.

So based on these three indicators, A. sediba seems like an australopithecine that might be slightly more orangutan-like than most. Why all the fuss, then? Well, because the authors claim that some of the features of the fossil specimens seem very much like those found in genus Homo, which is the genus to which human beings belong. For example, the authors think the coxal bones of the pelvis and the length of the lower limbs indicate that these creatures walked upright. Thus, even though their upper limbs are clearly adapted to life in the trees, the authors think their lower limbs were adapted to walking upright more than those of the australopithecines.

Of course, the problem with this is that in the adult specimen, no coxal bones are preserved, and in the juvenile specimen, only portions of the coxal bones are preserved. In addition, the only complete leg bone is the tibia in the juvenile. The rest of the remains of the lower limbs are fragmentary, and they mostly come from the juvenile. To make the bold claim that these creatures could walk upright based on such fragmentary evidence is risky, to say the least. I think the best you can say from these bones is that these creatures might have been able to walk on two legs, but it is not clear how comfortable this would be for them.

The other features that supposedly indicate these creatures are something other than australopithecines is that compared to typical australopithecines, the juvenile’s skull has a flatter face, a more projecting nose, and smaller teeth.

So notice what we have here. Using the adult, we have an ape that is a bit more orangutan-like than most australopithecines. Using the juvenile, we have many australopithecine features, but we also have some features that are closer to those found in genus Homo. That, as I see it, is the biggest problem with trying to say these creatures are anything other than specialized apes. It is very difficult to make decisions based on a juvenile skeleton. A juvenile skeleton is in the process of growth, and that can significantly distort the features paleontologists use to compare fossils.

Of course, I am not alone in this assessment. This study was published in the journal Science, and as is typical for that journal, a “commentary” article was published along with the scientific reports. In that commentary, we read:

But others are unconvinced by the Homo argument. The characteristics shared by A. sediba and Homo are few and could be due to normal variation among australopithecines or because of the boy’s juvenile status5

The article discusses two well-known paleoanthropologists (Dr. Tim White and Dr. Ron Clarke) who both think that this is either A. africanus or a “sister species.”

It is not surprising that Dr. White thinks these new fossils are australopithecines. In the chapter he wrote for The primate fossil record, he lays out seven “defining characteristics” of the australopithecines. 6 They are:

1. Leg/pelvis anatomy suggesting at least some bipedal locomotion
2. Large brachial index relative to other hominids
3. Sexual dimorphism (differences between the genders) between that of chimps and orangutans
4. Height between 1.2 m and 1.5 m
5. Cranial capacity between 350 cc and 600 cc
6. Teeth posterior to the canines relatively large with thicker enamel than extant apes and humans
7. Small incisors and canines compared to extant apes, and less sexual dimorphism in the canines

The fossils meet criteria 2, 4, and 5, and they probably meet 1 as well, at least from the standpoint that bipedal locomotion is possible. For 3, we know very little about sexual dimorphism, since we have only a juvenile male to compare to an adult female. For 6 and 7, we have mostly juvenile information, which is very hard to judge, especially when it’s the size that matters.

So the most scientific conclusion is that these fossils come from the genus Australopithecus, which is an extinct genus of specialized apes. That, at least, is what the data given by the fossils tell us, and it is probably why the authors put them in that genus. The authors’ idea that this is some ancestor of human beings is based on the hope that juvenile features can tell us a lot about adult features, and that is based on wishful thinking, not scientific reasoning.

REFERENCES

1. Berger, L.R., de Ruiter, D.J., Churchill, S.E., Schmid, P., Carlson, K.J., Dirks, P.H.G.M. and Kibii, J.M., “Austalopithecus sediba: A new species of Homo-Like Australopith from South Africa,” Science, 328:195–204, 2010.
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2. White, T.D., “Earliest hominids,” Chapter 24 in The primate fossil record, ed. W.C. Hartwig, Cambridge University Press, p. 413, 2002
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3. Brian G. Richmond, et al.., “Early hominin limb proportions,” Journal of Human Evolution, 43: 529-548 (fig. 7), 2002
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4. White, T.D., Ibid
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5. Balter, M., “Candidate human ancestor from South Africa sparks praise and debate,” Science 328:155, 2010
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6. White, T.D, Ibid, pp. 407-418
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Comments

14 Responses to “Australopithecus sediba: An Extinct Ape”
  1. jlwile says:

    Kevin, it is interesting that you link that particular video, since it basically says, “because creationists can’t agree on whether a fossil is distinctly human or ape, they must be wrong.” However, evolutionists take creationists to task ALL THE TIME for saying EXACTLY the same thing! Disagreement amongst scientists (even creation scientists) simply shows the deficiencies in the data. It’s not surprising that evolutionists can’t agree on whether or not A. sediba really is transitional, because the evidence is so sparse. In the same way, it is not surprising that creationists cannot agree on the classification of certain fossils, because the evidence is so sparse.

    By the way, the intro to the video indicates the author hasn’t been looking at fossils in the past few decades, as he claims there is a continuity of morphology in the fossil record. I agree that was one of Darwin’s predictions, but it has been dramatically falsified by the data. Because the data have so clearly falsified that prediction, evolutionists have had to desperately claim that evolution occurs in fits and starts so that there is no longer the expectation of continuous morphology.

  2. “So those who discovered the fossil think that it could be a direct ancestor of genus that contains modern humans. Do the data support this bold claim? Not at all. In fact, based on the actual fossils that have been published,1 A. sediba looks like nothing but a specialized form of extinct ape.”

    I freely admit the lack of anything conclusive, but I wonder why you eliminate one possible scenario: Why couldn’t the fossil be both a direct ancestor of Homo and a specialized form of extinct Australopithecus?

    I noticed your deliberately misleading use of ape instead of Australopithecus. Just what genera or species do you mean by ape in this quote?

  3. jlwile says:

    Shooter, the “direct ancestor” status depends on more similarities to Homo than other australopithecines. This is not the case. In fact, based on the brachial index, it is much LESS like Homo than other australopithecines.

    You really are a poor reader. I use the term “australopithecine” FOUR TIMES in the article. Thus, there is no misleading going on here. In addition, the australopithecines are clearly apes, so it makes sense to call them that.

  4. No, the conclusive direct ancestor status depends on DNA, which we are not likely to obtain. There will always be some murkiness about which non-Homo species were our direct ancestors. But that doesn’t mean we didn’t have non-Homo ancestors. What is your DATA that show we didn’t have non-Homo ancestors?

    Yes, australopithecines are apes, meaning the super-family Hominoidea. But you might be referring to the family Hominidae, or the great apes. Either way, Australopithecus is an ape. As are we, Homo. That is why is your use of ape is misleading, as you use the term incorrectly to try to make a false category distinction between Homo and other apes.

  5. jlwile says:

    Shooter, once again you seem to be behind the curve when it comes to what evolutionists are saying. You seem to think that DNA is the ultimate determination of ancestry, but that is simply not true. As a matter of fact, since the evolutionary relationships based on morphology are quite different from the evolutionary relationships based on molecular data, there is a large amount of disagreement among evolutionists as to what is the ultimate determination of ancestry. Indeed, if the “evo devo” community is right, then DNA won’t be a good indicator of relationships at all.

    The data that show we don’t have any non-Homo ancestors are very clear – we see apes and we see humans. We see nothing in between. Once again, here are some primers so that you can catch up:

    How Coherent Is the Human Evolution Story?

    The human fossils still speak!

    Making man out of monkeys

    You also need to catch up on some basic biology, as those in genus Homo are certainly NOT apes. As Science Daily says, “The differences between humans and apes are physically and functionally apparent, but genetically humans are extraordinarily similar to apes, especially to the chimpanzee and the bonobo (pygmy chimpanzee).” I know you have a difficult time with logic, so let me spell it out for you. If humans are apes, then there would be no way to discuss the differences or similarities BETWEEN humans and apes.

    Here’s another way you can educate yourself about the differences between humans and apes. As Andrew Lansdown humorously points out, “For example, like humans, apes have well formed rational faculties. Their ability to develop an argument, follow a line of logic, draw conclusions and frame hypotheses is quite remarkable. Also like humans, apes have a marked faculty for language. (This, of course, is intertwined with their powers of reason.) Their vocabulary is enormous, their grammar complex, and their conversations deep and meaningful.” He goes on like that for quite some time, showing that it is absurd to consider apes anything close to humans.

  6. Since you are ignoring the point I am making – in taxonomy, ape means the super-family Hominoidea – why don’t you explain to me how baraminology defines the term “ape”.

  7. “Indeed, if the “evo devo” community is right, then DNA won’t be a good indicator of relationships at all.”

    Cite your evo-devo sources to back this statement up.

  8. jlwile says:

    I am not ignoring your point. I have shown how absurd it is. People are not apes. Apes are a holobaramin. Thus, they are all related to one another by common descent. They include the non-Homo members of the Platyrrhini and the Catarrhini.

    I will use your favorite source to back up my “evo devo” statemtent:

    “Another focus of evo-devo is developmental plasticity, the basis of the recognition that organismal phenotypes are not uniquely determined by their genotypes. If generation of phenotypes is conditional, and dependent on external or environmental inputs, evolution can proceed by a “phenotype-first” route,[8][3] with genetic change following, rather than initiating, the formation of morphological and other phenotypic novelties.”

    Of course, if evolution proceeds by a “phenotype-first” route, then DNA comparisons would do very little to elucidate evolutionary relationships.

  9. How can you accept the infraorder Simiiformes (which only includes the parvorders Catarrhini and Platyrrhini), but not include Homo within that classification? That is, how do you justify your “Ape” holobaramin that includes everything in Simiiformes but the genus Homo? What is your taxonomic or systematic criteria for belonging to this holobaramin?

    As for my favorite source, I use it for basic background material, on general topics such as biological classification. I don’t pull quotes from it to use as proof of anything. In general, I also don’t start or stop quotes at convenient spots, as my comments on previous posts show. In this case you omitted the next sentence: “The case for this was argued for by Mary Jane West-Eberhard in her 2003 book Developmental plasticity and evolution.[8]”

    So we’re not talking about basic settled science such as the genera within orders and families. It’s a case. That’s how science works, in small starts and fits, dead ends and mistakes. Eventually settled science is accreted. Kuhnian paradigm shifts are few and far between. Don’t hold your breath until baraminology is accepted.

    But back to the quote. Here are two quotes from the abstract of reference 1

    “Moderate levels of phenotypic plasticity are optimal in permitting population survival in a new environment and in bringing populations into the realm of attraction of an adaptive peak. High levels of plasticity may increase the probability of population persistence but reduce the likelihood of genetic change, because the plastic response itself places the population close to a peak.”

    “Phenotypic plasticity is widespread in nature and may speed up, slow down, or have little effect on evolutionary change. Moderate levels of plasticity may often facilitate genetic evolution but careful analyses of individual cases are needed to ascertain whether plasticity has been essential or merely incidental to population differentiation.”

    If you want to really learn about Evo-Devo, then watch this and read this.

  10. Reference 1 of the Wikipedia article. We could trade quotes all day, but at the end of it, DNA will still be the gold standard to elucidate evolutionary relationships.

  11. jlwile says:

    Shooter, you really need to pay attention. The reason to exclude Homo from the ape holobaramin is quite simple: apes and humans are far too different to be related. You already learned that the chimp genome is ridiculously different from the human genome. You also learned that on a cognitive level, apes and humans are not at all alike. The systematic and taxonomic criteria are both genetic and behavioral, and they both argue that Homo is not related to the apes.

    Your poor reading skills are catching up with you again. Remember what I said. I said IF the “evo-devo” people are right, then DNA is not the final word on evolutionary relationships. I didn’t say it was “settled science.” Indeed, macroevolution in ANY form is not settled science. However, I did say that IF they are right, THEN genetics is not the final word, and the Wikipedia article clearly says that as well. Remember what it says:”Another focus of evo-devo is developmental plasticity…” Thus, this is not a “case” of evo-devo, it is a FOCUS. The specific article you mention is a CASE of developmental plasticity.

    It seems you are the one who needs to learn about evo-devo, as you don’t even know what its major foci are. You can learn about it here, here, and here.

    You can claim, “We could trade quotes all day, but at the end of it, DNA will still be the gold standard to elucidate evolutionary relationships,” but that just illustrates your desperation. As your own quotes demonstrate, DNA is not the gold standard for evolutionary relationships if the “evo-devo” people are right. After all, if “High levels of plasticity may increase the probability of population persistence but reduce the likelihood of genetic change,” then genetics will not tell us how the changes in phenotype took place and thus will not tell us about evolutionary relationships. If it can “speed up, slow down, or have little effect on evolutionary change,” then it will be impossible to know WHEN evolution is the result of genetic change and when it is the result of phenotypic plasticity.

    Please read the above links so you can learn what evo-devo is all about. After all, since you take evolution as infallible dogma, you need to know about its major sects.

  12. PLEASE stop projecting your religious worldview onto me and other evolutionists. Infallible dogma is antithetical to science. Sure, there are groups with opposing viewpoints about certain points, but they are not sects – they don’t base their membership on birth or rely on centuries-old divine revelation to find something to fight about.

    Here’s an example from The New Yorker of your religious worldview in action:

    And, while there are plenty of honest, capable people in finance, the ease with which investors looked past Wall Street’s failings seems like a classic case of what the social psychologist Leon Festinger called “cognitive dissonance.” Festinger argued that when beliefs come into conflict with reality we think up explanations that shape reality to our beliefs, rather than vice versa. He used the example of the Millerites, a millenarian religious sect that came to believe that Jesus Christ would return to earth on October 22, 1844. He didn’t. But not all the Millerites abandoned their faith. Many set about constructing elaborate rationalizations to justify their belief, arguing that Christ had returned spiritually, or that the event had occurred in Heaven, if not on earth. Similarly, when people’s faith in Wall Street as an honest broker, a smart allocator of capital, and a path to personal wealth was disappointed, they managed to explain things away.

    Happy Rationalizing!

  13. jlwile says:

    You have used the “projection” defense before, but it is transparently false. I am certainly not projecting. I am simply commenting on what is clear from your comments. You believe in the dogma of evolution with more fervent faith than that of most Christians I know. That is shown by how you must continually ignore the facts just to believe what you want to believe.

    I wholeheartedly agree with Leon Festinger’s concept of cognitive dissonance. Indeed, I see evolutionists employing it every day in order to claim they are being scientists while at the same time denying the clear implications of the data. Of course, you employ it in nearly every comment you leave.

    I am very happy using my rational capabilities. You might want to try that sometime rather than just fervently clinging to your faith in the words of the high priests of evolution!

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