by Matthew Cobb

It’s a big day for the evolution of our species! Tomorrow’s issue of Science contains 11 – yes eleven – papers describing the fossil skeleton of Ardipithecus ramidus, a hominid from 4.4 million years ago – the oldest such fossil ever found. As I write, the articles aren’t on line yet (and will probably require a subscription to read them completely), but the BBC and The Guardian both have substantial pieces on the discovery.

Briefly, a partial skeleton has been found of one female, together with bits and bobs of another 30 or so individuals,in Ethiopia. “Ardi”, as the female has been called, was about the same size and weight as a modern chimpanzee, but looked very different – many components (such as its hand) are more primitive than that of a chimpanzee,. This shows that the modern chimp hand is not the ancestral condition, but rather a highly evolved form.

Amazingly, the fossils were first found in the early 1990s, and it has taken 17 years to fully investigate them. It appears that Ardi could climb, but also walked on her knuckles [EDIT: no, she didn’t – she was BIPEDAL; mea culpa, and thanks to posters for pointing this out] walked on both legs; she ate fruit, plants and small mammals. Neither the males nor females had large canines – like us, but not like chimps. This suggests that strong male-male competition, which occurs in chimps, did not occur in our common ancestor.

However, despite the hype that will inevitably surround this amazing discovery (surely much more justified than the hoo-haa over Ida, the 47my old primate fossil), Ardi was not that common ancestor. Unfortunately, The Guardian calls her “our long lost mother”, but it is not yet clear exactly where she fits into our family tree. She may be an ancestor of Australopithecus – the species to which “Lucy” belonged.

The Guardian has this video snippet describing the discovery (upcoming from the Science website, I think) and this 10 minute MP3  file in which Tim White describes the link between Ardipthecus and the link with our last common ancestor with chimpanzees.

Now here’s a question – how will the creationists get out of this one?

EDIT: Science have just announced that all the papers, plus their magazine articles, will be available free here, later on today.

by Matthew Cobb

Jerry’s recent post about Steve Marley’s fantastic photo of a trilobite eye reminded me of one of the odder paleontological findings. Many trilobites have chunks taken out of them, presumably by predators. This fantastic CGI video – an extract of a display at the Chicago Field Museum – gives you some idea of what might have happened: at the end, a hapless Cambrian trilobite is snarfed by the top predator of the time, Anomalocaris. (This idea has recently been disputed by Whitey Hagadorn of Amherst College, who has made computer models which suggests Anomalocaris simply couldn’t have crunched the hard exoskeleton of a trilobite. Other people aren’t convinced and point out we’ll have to find some Anomalocaris poop to settle the issue…)

What’s odd about the munched trilobites is that, when you look at the distribution of injuries, you find a 2:1 ratio of injuries on the right hand side of the animals to injuries on the left-hand side of the animal. Like these:

This figure is taken from an article in Nature in 1989 by Loren Babcock and Richard Robison of the University of Kansas. The table showing the data (rather poorly reproduced below) is pretty convincing, but WHY?

The authors suggested that “those scars we attribute to sublethal predation… are significantly more frequently found on the right side of the trilobites, suggesting that predators preferred to attack that side”, and they pointed the finger at Anomalocaris.

There is a precedent for this kind of predator preference. In 1993, Michio Hori of Wakayama Medial College, Japan, reported in Science that scale-eating chichlid fish in Lake Tanganyika showed handedness and that “attacking from behind, right-handed individuals snatches scales from the prey’s left flank and left-handed ones from the right flank”. Maybe Anomalocaris (or some other Cambrian predator) showed similar preferences?

A few weeks after Babcock and Robison published their piece, Nature published two replies, one from David Maitland, the other from Stephen Stigler, contesting their interpretation.  Maitland suggested the apparent preference might be a consequence of the trilobites curling up to defend themselves (I don’t really follow his argument, to be honest), while Stigler, more interestingly, suggests this might be a problem of sample biais. Maybe the underlying assymetry is not in the predators, suggested Stigler, but in the internal organs of the trilobites: “it may be that trilobites were attacked equally often on both sides, but more of those attacked on the right side survived to join Babcock and Robison’s sample.”

That seems to have been the last word on the question, for the moment. But I am reminded of a study I heard about a while back, which was based on thousands of beachcombing records from the English Channel, where it was found (I think in Holland), that significantly more left shoes were washed up than right (or it may have been the other way round). I’ve been unable to track down this article, or any sensible explanation. All suggestions gratefully received!

P. Z. Myers got it right in a terrific response to a Christian’s advice about how atheists should behave more nicely.

Christian sez: 5. Try to deal with the actual notions of God seriously believed in by millions of people rather than inventing strawmen (or spaghetti monsters) to dismiss the concepts of God – and deal with the Bible paying attention to context and the broader Christological narrative rather than quoting obscure Old Testament laws. By all means quote the laws when they are applied incorrectly by “Christians” – but understand how they’re meant to work before dealing with the Christians described in point 3.

P. Z. sez: . . . .We atheists actually do address the claims fervently held by millions of people. The sneaky trick the theological wankers pull, though, is that once we’ve smacked them down, they announce, “Oh, no — we didn’t mean those millions of believers. They’re stupid. We meant these other millions of believers.” It’s a big game of whack-a-mole. What you call “obscure Old Testament laws,” someone else will call the core of their faith. What you value as the “Christological narrative,” a member of yet another sect will call pretentious confabulations.

Atheists just cut through all the noise and call it all sewage.

Yes, that’s it exactly. Whack-a-mole is what Terry Eagleton is playing, what Karen Armstrong is playing, what John Haught is playing — what the whole oleaginous and underemployed crew of academic theologians and their defenders are playing. But we needn’t address this bait-and-switch tactic any longer: we can just dismiss it as the WAM Argument.

Fig. 1. Oh noes, we’re talking about the faith over there!

Michael Sandel’s course at Harvard, “Justice,” is enormously popular, and is highlighted in today’s New York Times. The course is now being made free online, and can be found here.  There are videos of every lecture, and online study material.   You can neglect all the ancillary stuff, but this is a fantastic opportunity to see a great teacher for free, and I for one plan to watch every episode (there’s a new one every week, and two are already up).

I don’t expect that most people will have 45 minutes on a Saturday afternoon to listen to yours truly drone on about evolution, rationality, free will, and Robert Wright, but in case you want a break from football, Samantha Clemens has posted my radio interview with her that aired a week ago.

Also, just up on the National Center for Science Education website: three reviews of evidence-for-evolution books:  Andrea Bottaro reviews Kenneth Miller’s Only a Theory, Peter Dodson reviews Donald Prothero’s Evolution: What the Fossils Say and Why it Matters, and, coincidentally, Donald Prothero reviews Why Evolution is True.

Dodson is a bit critical of Prothero’s book (which I’ve praised highly here), and I want to say a few words about this.  Dodson calls out Prothero for being too harsh about creationism:

I do have a complaint, however. The book preaches to the converted. Its polemical tone can become wearying and may produce the unintended effect of nudging undecided readers in the wrong direction. Poorly disguising his contempt, Prothero’s rhetoric is sometimes over the top, as when he refers to “hard working, dedicated, self-sacrificing biologists who spend years enduring harsh conditions in the field” in contrast to “creationists who sit in their comfortable homes and write drivel” (p 113). Please! The facts of paleontology stand on their own. They do not need to be undermined by rhetorical shenanigans.

Richard Dawkins’s new book, The Greatest Show on Earth, was also criticized by several reviewers for being too hard on creationists — for labeling them “history deniers” and comparing them to those who would deny, for instance, that the Roman Empire ever existed.

I have to defend Dawkins and Prothero here (I haven’t suffered such accusations about my book) on two counts.  First, the whole need to write books like mine, Donald’s, and Richard’s comes from resurgent creationism.  You don’t write a book about the evidence for evolution in a vacuum: you have to have a reason, and the most pressing reason is that religiously-motivated creationists keep denying that evolution is true.  They offer the alternative hypothesis of creationism, whether it be Biblical literalism or intelligent design.  It therefore seems perfectly fair to discuss evolution as one of the two main going hypotheses for the origin and diversity of life, and to show — vigorously — that only the evolutionary alternative has empirical support.  You simply cannot do this without discussing creationists and their claims.

Second, most of us who teach evolution simply get frustrated with the witless nattering of creationists who refuse to honestly address the mountain of evidence for evolution.  Some of that frustration seeps into our writings. And that humanizes our writings. We are not emotionless drones; we have feelings and we show them. As Philip Pullman has pointed out,  one reason why Dawkins’s books are so popular is because the reader not only senses a human being behind the prose, but discerns what that person is like.

Now the degree of seepage varies: Richard, for example, talks more about creationism than I do.  But I don’t think that he, or Prothero, crosses the line into pure invective.

This, of course, is a matter of taste.  Some people like their evolution with a bit of bite, others like it completely unsullied by criticism of creationism. To each their own.  Certainly Dawkins’s and Prothero’s books have found legions of appreciative readers.  But more important is Dodson’s claim that Prothero’s rhetoric “may produce the unintended effect of nudging undecided readers in the wrong direction.”  This is the familiar claim that if we are too vociferous in criticizing creationism, its religious roots, or religion in general, we’ll actually turn people away from evolution.  Well, at least Dodson hedges by saying “may,” instead of asserting, like Mooney and Kirshenbaum, that it will nudge the undecided toward creationism. In the end, we simply have no data.  Maybe such rhetoric actually helps sell evolution.

Bjørn Østman discusses the matter (he thinks Prothero doesn’t go far enough!) on his website Pleiotropy (note the comment by Prothero).