Welcome to Superoceras, a blog about science and natural history, slightly biased towards paleontology and zoology, but inclusive of all sciences. Started in October of 2009, my goal is to communicate scientific knowledge (and the occasional piece of nonsense) in an informative and entertaining manner. Feel free to contact me with questions, comments, concerns, or criticism at superoceras(at)gmail(dot)com, and follow me on Twitter @Superoceras for all that and more in 140 characters or less!

Monday, February 01, 2010

Ardipithecus ramifications. (Science in the media part II)

Back in October, I wrote the first post in a series on science, education, and the media. Needless to say, I never got around to finishing that series, or answering the initial question of my friend regarding my thoughts on the (then) recent publication of papers and news articles on Ardipithecus ramidus, and the interpretation of the fossils by the scientist who claims that "apes descended from humans".

In the first part of the post, I did a quick overview of cladistics, and I hope that by the end of it, was effective in communicating that "apes" didn't descend from humans and that humans didn't decend from "apes" (like the chimpanzee), but that we are all in fact apes, and we all share a common ape ancestor somewhere down the branch of the family tree; the same tree that unites us to and with all living things on Earth. This might be a controversial idea to some, but the molecular, behavioral, and anatomical data confirms it. Life has been, and will continue evolving on this planet for as long as it remains habitable. Sometimes the relationships are distant, but they are there. Some people do not believe this. Others have never been exposed to the idea. But understanding evolution and the relationships of living things was only part of the problem I saw with my friend's question.

Another part of the problem was how the discovery and description of Ar. ramidus was publicized in the media. The journal Science published 11 articles on Ar. ramidus in a special October 2009 issue (which I highly suggest looking at if you already haven't). These articles are all peer reviewed in a scientific journal, done so specifically to ensure that each meets the journal's standards of quality, and more importantly, to ensure that the contributions made are scientifically valid. Five of those papers were authored or co-authored by Dr. C. Owen Lovejoy, the biological anthropologist I believe my friend was referring to in his question. Now I'll admit I haven't meticulously gone over every single word in every single article, but I'm pretty confident that no where in that issue of Science does Dr. Lovejoy say "apes descended from humans". But the headline of this TG Daily article does. The title reads: Ardi fossil shows 'apes descended from humans', but no where in the article does it actually quote Dr. Lovejoy as having said that either. In fact the only quote I saw was this:
"It has been a popular idea to think humans are modified chimpanzees. From studying Ardipithecus ramidus, or 'Ardi' we learn that we cannot understand or model human evolution from chimps and gorillas."
That seems pretty straightforward to me. This new discovery is changing what we know about the origin of our species. People used to think that bonobos and chimpanzees - our closest living relatives - were the ideal model for the anatomy and behavior of our ancestors. With this assumption, came the notion that there would be a linear progression from a chimp-like ancestor to modern Homo sapiens, with Australopithecus showing an intermediary between the two, and modern non-human apes representing a branch of the family tree that was "less evolved" from this common ancestor than we are.

This however, could not be farther from the truth. I've written before that no creature is "more evolved" than another, and that humans and chimpanzees share a common ancestor and simply went down different evolutionary paths, as opposed to having one "evolve from" the other. And the research published by Lovejoy et al. in the October issue of Science showed us just that. While behavior is a little harder (but certainly not impossible) to interpret from body fossils, we can learn a lot about anatomy from them, and Ar. ramidus helps put these assumptions to rest, once and for all. By studying the remains of "Ardi" we can see that the anatomy of living non-human apes is not primitive as once thought, but rather, derived and evolved specifically in these organisms. For this reason, we can't use living non-human apes as models of human ancestors. Pure and simple.

Ardipithecus ramidus
shows us, more than any fossil species currently known, what the most recent common ancestor (or concestor) between Hominina (modern Homo and their bipedal ancestors and relatives) and Panina (modern Pan and their quadrapedal ancestors and relatives) would have looked like. But WAIT! Let me be clear about one thing: it may be the closest representation we have yet to discover of this concestor, but it is NOT the concestor of the Hominini (Homininia+Panina) clade. Ar. ramidus is very clearly on our branch of the family tree, not the "chimp" branch. Of this there is no doubt, as it has anatomical adaptations that allow for upright walking and a very human set of canine teeth, among other things (Lovejoy 2009). So "chimps" certainly didn't evolve from Ar. ramidus, and there is no way to know for sure if modern humans did. The species simply represents the best analog we have so far.

The articles published in Science are a bit technical, but they provide a wealth of information for those interested in learning about "Ardi", or human origins in general. And they are readily available to the public, as are many journals. A quick search using Google Scholar yields much better and more reliable sources than does Wikipedia (although I have to give Wikipedia users some credit for linking to sources now and citing references from time to time). But the trouble is, most people don't use Google Scholar, or look to technical journals for their information. The result is a quick search for "facts" that often results in the discovery of something that might not be. Either that, or misrepresentation (whether deliberate or unintentional) of material. I think this is the case in the TG Daily article from above, or whatever other source my friend was getting his information from. Mainstream media outlets don't do a lot of well researched science journalism, but they love to report on new findings. That might be a bit presumptions and derogatory of me, but I know for a fact that something published in an online news article has not been researched and reviewed to the point that something published in a peer-reviewed journal has. And this causes problems, because it puts ideas into the minds of the general public that are not true, or founded in good science. This is bad. This is very, very bad.

Branching diagram to illustrate phylogenetic relationships of extant (with solid lines) and extinct (with dotted lines) hominids. Numbers represent evolutionary derivations and shared traits among the groups. Note that Ardipithecus ramidus and Australopithecus afarensis (a.k.a. "Lucy") are shown as sister species to our own, and not direct ancestors. (Click to enlarge.)

But what does this mean? And what does it have to do with the question my friend asked me? Well, this still isn't the whole story, but this is another piece of the puzzle. Piece one is that, humans didn't descend from "apes" and that "apes" didn't descend from humans. Piece two is that, as far as I can tell, a scientist never said that "apes descended from humans" in the first place, but that rather, a news outlet picked up on a story and reported on it without doing their homework. And piece three... well, you're going to have to wait a little longer for that. But don't take my word on any of this. I try and only present information on this blog that is current, accurate, and can be backed up with references. But I encourage each of you to go out and explore this phenomena (among other things) for yourselves. Gather data. Look for sources. Discover things on your own. That's what good science is all about. With that in mind, I will leave you with a few stories, ripped from the headlines, that illustrate my point to perfection. Feel free to explore the topics presented below on your own, or wait until the next post, in which I will discuss them, and my final thoughts for this series, which I promise, will come a lot sooner than this one did.

"Fossil Ida: Extraordinary find is 'missing link' in human evolution"

"The terrifying flying dinosaur that could unlock the mystery of human evolution"

"Venomous Dinosaur Discovered--Shocked Prey Like Snake?"

Lovejoy, C. O. 2009. Reexamining human origins in light of Ardipithecus ramidus. Science 326, 74.

Figures (in order of appearance)
1) Ardipithecus ramidus reconstruction illustration © J. H. Matternes, 2009.
From Gibbons, A. 2009. A New Kind of Ancestor: Ardipithecus Unveiled.
Science 326, 36-40.
2) Composite photograph of "Ardi" fossil skeleton
(ARA-VP-6/500), credit © T. White, 2008.
From Hanson, B. 2009. Light on the Origin of Man.
Science 326, 60-61.
3) Hominid cladogram illustration © J. H. Matternes, 2009.
From Lovejoy, C. O. et al. 2009. The Great Divides: Ardipithecus ramidus Reveals the Postcrania of Our Last Common Ancestor with African Apes. Science 326, 100-106.

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