Comparing Apes With Fossils

Forgive the awkward title. There are a wide variety of misunderstandings about how paleoanthropologists practice their science. While I am reluctant to continue flogging dead stinky horses, a good example of a common misconception occurred over at UD. You may remember this post of Orac’s lamenting the embrace of ID by David Cook, MD. Mr. Cook has also made some comments concerning paleoanthropology that I would like to discuss, as they display some common, and widespread, misunderstandings of paleoanthropology. I was going to pass over Mr. Cook’s comments in silence, but since I have encountered similar comments in a wide variety of places I finally decided to write something and address them.

In a follow up comment at UD Mr. Cook comments:

The recent front-page story on the ancient skull discovered in Kenya, and your editorial of March 24 about it, are perfect examples of the tautological reasoning which cripples real advances in the study of the origins of life. There is nothing about that skull itself, taken without preconceived assumptions, to suggest that it is an ancestor of modern humans.
Here is how it goes; an anthropologist discovers an old skull or skeleton. Since he knows that humans descended from earlier primates, he immediately interprets the old bones as probable ancestors of humans. He then announces that he has discovered more evidence that humans descended from primates.

A little later in the same comment he says:

What was actually discovered in Kenya was a very old primate skull. Period. Everything after that is inference. To me it looked like a gorilla, or other great ape. How many great ape skulls have been left lying around Africa over the years?

Leaving aside the fact that Mr. Cook failed to support the latter contention with any kind of evidence, the implication is that paleoanthropologists are incapable of telling the difference between apes and humans. Or perhaps, that they don’t consider primate anatomy when discussing fossil finds. How accurate is this characterization of paleoanthropology? In a previous post I compared the anatomy of Chimps, gorillas, orangutans and Australopithecus afarensis and I don’t propose to go into details concerning the differences between apes, humans and hominin fossils. What I would like to look at is the use of comparative material.
Let’s start with Pierolapithecus catalaunicus. P. catalaunicus is an ape dating to approximately 13 million years ago. It is an important fossil because it is close to the last common ancestor of great apes and humans. When Moya-Sola et al announced the find, however, they did not just make a series of assertions and then claim that P. catalaunicus was close to the last common ancestor of the great apes and humans. They compared it to a wide variety of extant and extinct apes and cercopithecoids. For example, they compared P. catalaunicus to Dryopithecus, Proconsul, Ouranopithecus, Morotopithecus (among other extinct primates), Hylobates, Ateles, Pongo and Papio (among other extant primates).
When Brunet et al announced the discovery of Sahelanthropus tchadensis they compared it to Pongo, Pan, Gorilla, Samburupithecus, Ouranopithecus the australopithecines (including Paranthropous), Ardipithecus, Homo habilisand Kenyanthropous among others.
When White et al announced the discovery of Australopithecus ramidus (later transfered to the genus Ardipithecus) they compared it to the other australopithecines, Pan, Gorilla, Sivapithecus, Kenyapithecus, Ouranopithecus, Dryopithecus, and Lufengpithecus among others.
When Asfaw et al announced the discovery of Australopithecus garhi they compared it to the other australopithecines, early Homo and Pan
When Senut et al announced the discovery of Orrorin tugenensis they compared it to the other australopithecines, Ardipithecus, Pan, and Gorilla.
The point to take away from all of this is that when paleoanthropologists announce a new species they are expected to compare it to other relevant species, be they extinct or extant. This practice of comparing a new species to other species is also prevalent in paleontology. In fact I seriously doubt a new species could be named without this kind of comparison (in technical jargon it is called a diagnosis). What about other uses of comparative material? How often, outside of naming a new species, do paleoanthropologists compare there fossils to extant species of primates? I will only give a few examples of this in order not to bore you.
Richmond et al compared a 16 million year old ulna to a wide variety of extant and extinct primates.
Senut et al (2004) compared the scapula and clavicle of Nacholapithecus kerioi to 15 extant primates as well as Proconsul heseloni, Ugandapithecus major, and Equatorius
Young used cladistic analysis, principle components analysis and cluster analysis to examine the post cranial anatomy in a wide variety of extant and extinct primates.
One final study. Alemseged et al (of Dikaka fame) examined fragments of the frontal, both temporals, occipital, parietals, and the right maxilla of some previously undescribed fragments from Omo. Part of the examination consisted of comparing the morphology displayed by these fragments to similar bones in Australopithecus aethiopicus, A. boisei , and A. robustus.
The above examples are not exceptions to the rule. I could spend the next week cataloging all the articles that compare primate anatomy with fossil material and still not exhaust the literature. In reality, comparing finds with extant and extinct primates forms one of the central missions of paleoanthropology. Comparative material exists in a wide variety of museums, anthropology departments and medical schools. Over and above that, a large part of the education of a paleoanthropologist consists of learning primate anatomy (both skeletal and soft tissue). In point of fact, any paleoanthropologist who didn’t compare his fossils with other extant and extinct species wouldn’t be taken to seriously.
One final point. I frequently hear people claim that a given hominin fossil “looks like” an ape. This is remarkably vague, although perhaps forgivable if one doesn’t know that much about skeletal anatomy. Given the abundance of comparative material, however, this is something that can be looked at metrically (by taking measurements on relevant variables and performing various statistical analyses) and non-metrically (via the analyses of specific morphological characters). Consequently, when you here some one asserting that a fossil “looks like” and ape with out further specification you can assume that they are either being deliberately evasive or they do not know what they are talking about (or both).
Literature Cited (in order of appearance)
Moya-Sola et al (2004) Pierolapithecus catalaunicus, a New Middle Miocene Great Ape from Spain. Science 306:1339-1344
Brunet et al (2002) A New Hominid from the Upper Miocene of Chad, Central Africa. Nature 418:145-151
White et al (1994) Australopithecus ramidus, a New Species of Early Hominid from Aramis, Ethiopia. Nature 371:306-312
Asfaw et al (1999) Australopithecus garhi: A New Species of Early Hominid from Ethiopia. Science 284:629-635
Senut et al (2001) First hominid from the Miocene (Lukeino Formation, Kenya). Earth and Planetary Sciences 332:137-144
Richmond et al, 1998 First Hominoid from the Miocene of Ethiopia and the Evolution of the Catarrhine Elbow, Vol 105:257-277
Senut et al (2004) Preliminary Analysis of Nacholapithecus Scapula and Clavicle from Nachola, Kenya. Primates 45:97-104
Young (2003) A Reassessment of Living Hominoid Postcranial Variability: Implications for Ape Evolution. Journal of Human Evolution 45:441-464
Alemseged et al (2002) Hominid Cranium From Omo: Description and Taxonomy of Omo-323-1976-896. American Journal Of Physical Anthropology 117:103-112

11 Responses

  1. You’ve got an un-closed A tag on “previous post”. You also have mangled HTML in the paragraph that starts with “When Asfaw et al announced…” The word “Homo” has no end EM, just two starts. 😉

  2. Excellent. I wonder if Cap’t Hook, I mean Dr. Crook, I mean, Dr. Cook, was paying attention, or sleeping in the back row again?

  3. BTW, this is an excellent post. I get so sick of laypeople blaming experts for their own ignorance. I know one person who does this. He’s something of an expert in plants, so I might throw down a part of plant, ask him what it’s from, then call him a liar to his face when he tells me. “How can you know from just a small part? It’s impossible. You’re just making it up to sound impressive. Liar.”

  4. F*&^%@# HTML tags! They are all fixed now, vastly improving the readability. Of course, if I were Dembski I would have just said “It is not my responsibility to match your pathetic level of closed HTML tags…” and left the post as it was.

  5. You know, it’s funny how people think….I have argued in the past with creationists/science deniers in the past about this very thing. They beat the drum about how the experts have it wrong and how paleoanthropology (or evolution as supported by its many many lines of evidence) is all a conspiracy by the scientific elite.
    And yet, as an “expert” myself in the computer and electronics repair business, those same people are the first to call me when their machines are misbehaving. And they usually expect me to work for free! I asked such a person once how they could trust my knowledge and skills. I posed to him the idea that the mega corporations of the world might part of a massive conspiracy involving certifications etc… His response? It would be impossible for a conspiracy like that to survive, that the American people are too smart and besides someone would be bound to talk! Oohhhh, the delicious irony.
    Anyway, I’ve rambled enough. Great post BTW; and thanks!

  6. Well supported post! I have come across this misconception often too and I appreciate that you took the effort to show how big time discoveries were made using comparactive analysis. I wonder if its because people just don’t know how paleoanthropology works? What do you think, why is this misconception… this misunderstanding… on how paleoanthropologists draw their conclusions so prevalent? It’s clearly outlined in the methodology sections of all of these papers!

  7. I can think of a number of reasons. Part of it is a lack of knowledge about the field of paleoanthropology (and the way it is romanticized in the press). Americans don’t like to appear ignorant so if asked about a subject they will make something up just to avoid appearing ignorant. Red State Rabble has a link to a video that illustrates this perfectly, unfortunately YouTube seems to be down at the moment. Religious preconceptions play a role as well, these kinds of misconceptions (and basically what they are saying is that paleoanthropologists are not smart enough to know what they are talking about – hence mistaking apes and monkeys for hominins) make it easier to dismiss paleoanthropology. In other words, it is partially boundary maintenance (ala Peter Berger) that serves to keep the outside world from impacting ones worldview…

  8. “What do you think, why is this misconception… this misunderstanding… on how paleoanthropologists draw their conclusions so prevalent?”
    Personally, I think it is wilful ignorance: simply another case of people using their worldview to filter the evidence, instead of letting the evidence filter their worldview.

  9. Sure, that is part of it, especially among creationists. How many people, though, are going to read an article in the paper about a fossil and then be able to go find more info in the scientific literature. It may be second nature to me to go to Science, Nature, PNAS, AJPA, or the Journal of Human Evolution (an issue of training rather than intellect or worldview)? Take the recent stories about gene introgression in Neanderthals, how many people would be able to track down those articles in the literature, plus any supporting literature they might need to make sense of the subject?

  10. Not to be waging my Open Access war on this issue, but I believe some of the misconception has to be due to the lack of open access to scientific research, like paleoanthropolgical finds. Journals like Science and Nature are largely closed access, and lay-people can’t get first hand accounts of what was studied, how it was studied, and how conclusions were drawn. Instead all they get is third hand accounts on the AP, which distorts some of the facts. Although it’s not the entire case, I do believe more people will be informed of whats actually happening behind the findings if they actually had the first hand report.

  11. Wage away Kambiz! I entirely agree that that is part of it.

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