Kenyanthropus

In the fossil record, a species is a hypothesis. We can't test that hypothesis in the way we do with living animals. Even in the dark, after all the paleontologists have left, the fossil bones just won't get it on. No reproduction, no test.

So, sometimes we have to live with hypotheses that we can't immediately test. Because many hypotheses are wrong, we have to keep juggling in our minds the names of more species than probably existed.

All the juggling frequently leads to confusion. One may reasonably wonder how we know that species X evolved into species Y, when half the field rejects the hypothesis that X was a real species. Often we don't disagree about the "evolving into", but we do disagree about the boundaries and other relationships of the populations -- which we can understand only indirectly from the fossils. The fossils don't change, but our hypotheses about them do.

That brings us back to A. anamensis. Here's a hypothesis about an ancient lineage of hominins, based on a certain number of differences from later fossil samples assigned to A. afarensis. That's a precarious place for a hypothesis, because from the beginning, the definition of A. afarensis has encompassed geographic and temporal variability. How hard would it be to recognize a little more temporal variability? Not very.

So, as I described last week, Haile-Selassie and colleagues (2010) propose sinking A. anamensis ("Woranso-Mille: A ladder not a bush"). I should mention, if I haven't already, that I have great sympathy for this viewpoint. Absent some compelling evidence that the lineage includes a speciation event, I prefer slow gradual anagenesis to be categorized into one evolving species, not an arbitrary set of chronospecies.

In the same post, I described the work of Kimbel and colleagues (2006), who had argued for anagenesis in the same sample of A. anamensis and A. afarensis-referred fossils, but retained the two distinct names for them. One thing stands out as a mystery to me in that paper. Why didn't they let Kenyanthropus make the argument for them?

If you want to establish that A. anamensis is taxonomically valid, the simplest way to answer all critics is if it has more than one descendant. You don't have to demonstrate the phylogeny beyond all doubt, I would say, you just have to take the hypothesis seriously.

In this instance, we seem to have two good candidates for a non-A. afarensis descendant of A. anamensis. The more obvious of them is Kenyanthropus. Why didn't they advance the hypothesis of a A. afarensis-Kenyanthropus clade? Here's what Kimbel and colleagues wrote about the latest Leakey find:

A more significant concern is the presence of Kenyanthropus at 3.5 Ma. Kenyanthropus may demonstrate cladogenesis prior to this time, but this taxon is only directly relevant to the analysis if any of the samples share derived character-states with it. At present, the Kenyanthropus hypodigm does not match the others in the availability or quality of character data for the mandible and anterior teeth, while the evidence that exists (from the maxilla, for example) does not suggest a close relationship of Kenyanthropus to any of the phena considered here (Leakey et al., 2001).

So, they took the hypothesis off the table. And again, they've refocused the question solely upon dental and mandibular evidence.

This is a very large hole. At 3.5 million years, KNM-WT 40000 is earlier than any other comparably complete hominin skull, except for Ardi and Toumaï. It doesn't look like them, that's for sure. Not the same phenum at all. If you're going to insist that KNM-WT 40000 isn't A. afarensis, it's hard to see a better hypothesis than that it's descended from A. anamensis.

If it doesn't have a close relationship to either A. afarensis or A. anamensis, then I'm at a loss to figure out what they think it is related to!

I'm willing to believe White's (2003) argument that it just is a member of the A. anamensis-A. afarensis lineage, but I don't see the contrary argument that it's so different from this lineage that it must be derived from some as-yet-undiscovered hominin. Keep in mind that the argument was formed by people, many of whom already knew basically what Ardi's skull was going to look like. I just can't feature why this phylogenetic problem didn't raise itself to a higher profile.

As I wrote above, we juggle more hypotheses than can be true. In this instance, the null hypothesis is that all these hominins belong to a single evolving species, which would be called A. afarensis. But one alternative, in which A. anamensis existed as the ancestor of A. afarensis and at least one other species, has some utility. It lets us refer clearly to phylogenies with late-diverging sister taxa. As Yoda might have said, there is another possible sister taxon for A. afarensis: A. africanus might be derived from, or might itself be, a South African contemporary of the Hadar-Maka-Laetoli sample. The earliest Sterkfontein dates go up and down; one or more of the remains might be contemporaries of Laetoli or even earlier East African localities.

Anyway, I'm not so interested in this question of bushes versus ladders, or "Pliocene diversity". I'm more focused on the curiously non-hominin-like features of Ardipithecus. If we suppose a late molecular divergence of hominins and chimpanzees (say after 4.4 million years ago), then Ardipithecus might be an ape or ancestral (stem) hominid, not a hominin. If so, then samples now referred to A. anamensis, including later specimens from Aramis, Asa Issie, and Kanapoi, are in fact the earliest-known members of the human lineage.

A. anamensis is no afterthought in that case, it may be the stem hominin.

That is, if it hasn't been sunk into A. afarensis.

UPDATE (2009-12-10): A reader writes to remind me about A. garhi, which presents itself as very much like A. africanus and is quite a lot later than any known A. afarensis samples. One alternative is that A. africanus is simply the latest element of the single A. anamensis-A. afarensis-A. africanus anagenetic sequence.

I don't think that's very easy to reject, considering the lack of good cranial remains between 3 and 2.5 million years ago (or for that matter, even later) in East Africa.

Some of the Sterkfontein specimens, particularly those from Jakovec cavern and from Member 2 (including Little Foot) have been suggested to be older than 3 million years. Partridge and colleagues (2003) put them at older than 4 million years ago, which would make them rivals of A. anamensis as the earliest hominins. But Berger and colleagues (2002) argued (apparently preemptively) that these early dates are not necessary on faunal or magnetostratigraphic grounds.

A second reader wonders why I didn't mention A. bahrelghazali as a possible sister to A. afarensis. Well, nothing's impossible, but I'd say the case for the Bahr el Ghazal mandible being distinct from the Hadar-Maka-Laetoli sample isn't very strong. Still, we're only talking about hypotheses here, I suppose.

References:

Berger LR, Lacruz R, de Ruiter DJ. 2002. Revised age estimates of Australoipithecus-bearing deposits at Sterkfontein, South Africa. Am J Phys Anthropol 119:192-197. doi:10.1002/ajpa.10156

Haile-Selassie Y, Saylor BZ, Deino A, Alene M, Latimer BM. 2010. New hominid fossils from Woranso-Mille (Central Afar, Ethiopia) and taxonomy of early Australopithecus. Am J Phys Anthropol (in press) doi:10.1002/ajpa.21159

Kimbel WH, Lockwood CA, Ward CV, Leakey MG, Rak Y, Johanson DC. 2006. Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record. J Hum Evol 51:134-152. doi:10.1016/j.jhevol.2006.02.003

White T. 2003. Early hominids -- diversity or distortion? Science 299:1994-1996.

Suwa G, Asfaw B, Kono RT, Kubo D, Lovejoy CO, White TD. 2009. The Ardipithecus ramidus skull and its implications for hominid origins. Science 326:68e1-68e7. doi:10.1126/science.1175825

Leakey MG. Spoor F, Brown FH, Gathogo PN, Kiarie C, Leakey LN, McDougall I. 2001. New hominin genus from eastern Africa shows diverse middle Pliocene lineages. Nature 410:433-440.

Partridge TC, Granger DE, Caffee MW, Clarke RJ. 2003. Lower Pliocene hominid remains from Sterkfontein. Science 300:607-612.

In a new paper, Yohannes Haile-Selassie and colleagues describe new hominin fossils from Woranso-Mille, Ethiopia. A good thing: It gives somebody like me a rationale for describing early hominins from the point of view of Hadar. You see, Hadar is the first sample to include a really complete skeletal representation. You can present earlier sites as a series of "firsts", but that's kind of misleading. Now, the simple Ardi-Lucy comparison carries a lot of water for teaching early hominins, and if we can assume that the samples intermediate in time are mostly A. afarensis-like, so much simpler.

Oh, and one more really good thing: Standard dental measurements are provided in the text of the paper. Thank you, AJPA! We may not get all the specimens, but at least we can check the statistics.

But there's a chance that things are not so simple as they seem, that there are mysteries still waiting to jump out of this sample and scare us at night. I imagine that some people are less than thrilled about this paper, which explicitly rejects the reality of one Leakey-named species and ignores another into obscurity. One might expect me to welcome our new lumping taxonomic overlords. And yet, this little paper doesn't provide some information and comparisons that seem like curious omissions. Which makes me wonder...

The fossils from Woranso-Mille are between 3.6 and 3.9 million years old -- basically older than Laetoli and younger than Kanapoi. Since the Laetoli sample is A. afarensis, and the Kanapoi sample is A. anamensis, we can expect that the Woranso-Mille sample would say something about how these two species were related to each other. The fossils might be one species or the other, they might be intermediate between them, or they might even be something altogether different.

What is there?

The sample as described is almost exclusively dental, with only a fragment of mandible and another of maxilla tossed in the mix.

Some readers may have been under the impression there's more at this site, and indeed I am as well. I think I've even seen them for 500 milliseconds at a meeting once upon a time. Of course, maybe that was a dream. Much in paleoanthropology seems to be fading into a unicorn fairyland these days...

Wait a minute! It's for occasions like this that I have a blog! As it turns out, I took some notes on Woranso-Mille back in 2007.

Now, I have to warn you: These notes were so snarky that I didn't dare hit "publish". But there's no sense shirking responsibility for them now. Next thing I know, some crank will be hacking my server to bring all this snark into the open!

Along with many other people, I got to see the hominids from Woronso-Mille this spring. Then again, see is probably an overstatement. I mean, when you see something, generally light waves from the objects actually have time to strike your retinas. I couldn't swear that anyone actually had that experience during Yohannes Haile-Selassie's talk to the Paleoanthropology Society. Sure, there was a subliminal impression that the pictures were there. And yet, Powerpoint and automatic timing can do magical things.

I experimented a bit later, to try to estimate just how long the pictures had been up there. The 500 millisecond setting seemed about right. Definitely automated. Too short for microsaccades to bring in the edges of the fossils properly. And many of them were in situ photos, with a lot of brown-on-brown. Hard to pick out edges at all, and some edges were still in the ground.

I mean, really, work out the time that Santa Claus has to spend in each kid's house on Christmas Eve to make it to all the world's children in one night. That's the kind of time we're talking about.

See what I mean. I mean, that's over-the-top snark. Still, it's better material than I usually work with, so I can't for the life of me figure out why I didn't publish it. It goes on:

Don't get me wrong. I think it's entirely appropriate to hide the images, dim them, heck, don't even show them if they don't want to. Think of all the yokels like me who could tell immediately from a decent picture whether the fossils were A. afarensis or not, and go shooting off their servers to the rest of the world. Hard work in the field, with the high risk of failure, deserves every possible reward -- certainly the right to take the necessary time to make a careful analysis. I hardly ever make any comments after I hear a public talk, unless the material is already well-known or described elsewhere. And there are other practical reasons not to talk about it -- for one thing, people sometimes change their minds!

But why should I feel any compunction about prognosticating on fossils that are announced in the press? Hey, if they didn't want the attention, they wouldn't have a press conference, right? I'll bet they didn't make the press sit through the half-second slide show!

Haile-Selassie announced several of the Mille fossils in 2005, notably the partial skeleton -- of which they are still trying to find more parts. At the time, I wrote about it, Rex Dalton wrote about it, Ann Gibbons wrote about it, twice, the AP wrote about it. Good times were had. Oh, those good times. Sure, no descriptions. Granted, in situ brown-on-brown photographs with buried edges. But good, good times.

How could I have forgotten those good times?

Now, there is a second press offensive underway. The best stories are at National Geographic News and The Cleveland Plain Dealer (Haile-Selassie's in Cleveland). It's an important site, with dozens of specimens.

Hey, maybe they're like the Laetoli footprints and they rebury them when they're done looking at them. Kind of like catch-and-release.

The stealth mandible

All this was nearly three years ago. Which is a bit strange, considering that the current paper still doesn't include all the specimens. Assuming the 2007 illustrations were correct, the current paper doesn't even include all the Woranso-Mille dental specimens, as at least one mandibular dentition appears to have been omitted. It is, of course, possible that the news reports had the wrong picture.

Here are my 2007 thoughts on the matter:

We can probably answer this already: the National Geographic story includes a picture of the most complete mandible, and it looks an awful lot like LH 4, maybe with a more sloping symphysis. It's a rotten view - artistic, sure, but a lousy angle for comparison.

This mandible is not included in the current paper. It is pretty obviously the most diagnostic of the mandibular/dental specimens, if it's from Woronso-Mille. I wonder if National Geographic really may have credited the wrong photo to Haile-Selassie? Very strange. In any event, it's an important question since the sample of other postcanine teeth in the paper is generally 2-3 specimens. A missing postcanine dentition would make a lot of difference to our picture of the variation.

OK, continuing on:

But still, the teeth appear to fall into the Laetoli-Maka-Hadar sample, the postcanine rows diverge from each other, and the symphyseal morphology in A. afarensis is certainly variable enough to encompass this mandible. Really the only missing feature that would be helpful is the P₃, but unless other specimens turn out to be outside the Hadar range, I would assume this is going to be assigned to A. afarensis.

Which does make me wonder how much the hidden mandible has driven the paper's conclusion. On the basis of the specimens they published, the majority of dental features seem to argue in favor of A. anamensis, as they explicitly write. They mention only a few "derived features" also present in later sites. Given the date, one might just as easily argue that these "derived" features were actually low-frequency variants heretofore unrecognized in the small A. anamensis sample, so that Woranso-Mille extends the range in that species while maintaining its overall anatomical pattern. The stealth mandible, if indeed it exists, looks more persuasive fitting in the pattern of A. afarensis.

The unanswered phylogenetic questions are chiefly about what other lineages there may have been at the time. Mille might answer that question if substantial hominid diversity were found there, or at least something really different from the other sites. But no apparent evidence of such diversity was apparent in the public lecture. Maybe there are surprises waiting, but this team in the past has argued pretty strongly for taxonomic conservatism.

On the other hand, this is what Haile-Selassie told the Cleveland Plain Dealer:

"The current hypothesis, which so many people seem to accept, is that they were ancestral descendents [sic, I'm assuming that's a misquote]- that anamensis gave rise to afarensis," Yohannes Haile-Selassie, expedition co-leader and anthropology curator at the Cleveland museum, said in a phone interview from Addis Ababa. "To test that, we need fossils. That's why we think these specimens are really, really important."

Sinking A. anamensis

In their current paper, Haile-Selassie and colleagues conclude the following:

The Woranso-Mille hominids are significant for understanding the evolutionary history of early Australopithecus, particularly due to critical placement within a previously poorly known time period, 3.5 and 3.8 Myr. They are of paramount importance in testing hypotheses about the ancestor–descendant relationship between Au. anamensis and Au. afarensis. The Woranso-Mille hominids shed some light on whether Au. anamensis and Au. afarensis are two distinct species, or parts of a single evolving lineage undergoing morphological change through time. Dentally they are more similar to Au. anamensis from Allia Bay than to Au. afarensis from Laetoli. However, they also share some derived characters with Au. afarensis from Hadar and Laetoli. Based on the currently available evidence, the Woranso-Mille hominids are temporally and morphologically intermediate between the more primitive Au. anamensis from Allia Bay and the slightly derived Au. afarensis sample from Laetoli (Ward et al., 2001; Kimbel et al., 2006). They appear to potentially represent a transitional population within an anagenetically evolving Au. anamensis-Au. afarensis chronospecies (White et al., 2006; Kimbel et al., 2006) providing further support to the well-established hypothesis of ancestor–descendant relationship between the two species. To test this and other alternative hypotheses rigorously, and elucidate the evolutionary history of early Australopithecus, more complete fossil specimens are needed from the critical time period between 3.6 and 3.8 Myr. However, what appears to be evident with the discovery of new fossils spanning the 4- to 3.5-Myr interval is that morphological differences between Au. anamensis and Au. afarensis do not warrant a species level distinction (emphasis added).

Buh-zaaaaaaam! All your species are belong to us! Kenyanthropus? We won't even dignify it by using the word. A. anamensis? Sunk like the Bismarck.

The fundamental debate here is semantic. Everyone seems to agree that anagenesis (that is, gradual evolution over time) is a likely hypothesis for this lineage. Where they disagree is how to handle the taxonomy.

1. Strict cladists want to name species based on the appearance of unique features (that is, phylogenetic species), in which case A. anamensis is a species, A. afarensis is a later species with new characters, and very possibly we need to resurrect Praeanthropus africanus for the Hadar sample, even if it mostly overlaps, since it has a few characters never found earlier and represents a broader sample of postcranial anatomy, which is entirely unknown at earlier sites.

2. Strict users of a Wiley-like Evolutionary Species concept always place anagenetic lineages into one species. So, the single lineage hypothesis lumps A. afarensis and A. anamensis together. And as Haile-Selassie and crew go on to point out, we might even lump Ardipithecus, if it's the lineal ancestor of the later hominins.

3. Not-so-stickly people, which is most everybody, pretty much recognize species along with the crowd. A. anamensis has a history now. It's not just early A. afarensis, because, well, lots of people said so. And after all, you can tell the difference between them if you look carefully.

What's interesting (at least to me) is to read Kimbel and colleagues' 2006 paper, keeping in mind the "following the crowd" scenario 3. In this light, much of that paper is boundary defense. A. anamensis had already elbowed its way into the textbooks, and the paper recognizes the existing taxonomy without attempting any revision. But the demonstration of anagenesis within A. afarensis would be sure to provoke some strict cladists to name some more species -- a species for Hadar, for example. Kimbel and colleagues reiterated that anagenesis within A. afarensis is expected -- it's part of the species' literature, now. So the paper tried to draw two lines in the sand: on the one hand, A. anamensis is real; and on the other hand, no further distinction within A. afarensis is warranted. Taxonomic containment.

Just a pelvis away...

But, drawn in this way, both lines in the sand might be washed away by a single discovery. The present pattern of evidence is mostly dental and mandibular. Woranso-Mille may be only one postcranial specimen away from lacking a bunch of derived postcranial characters that are well-evidenced at Hadar.

After Ardi, I think this is a serious possibility because of the scope of postcranial innovations at Hadar that are not evidenced anywhere earlier. It could be that all the postcranial traits of Lucy and her kin are lineage-typical, going back all the way to Kanapoi (and don't forget the A. anamensis from the Middle Awash). But we don't know this. Given Ardi, it appears that the adaptive package appeared rapidly, after 4.2 but before 3.5 million years ago. It seems to me that there's every chance that A. anamensis, and possibly the Woranso-Mille sample, hadn't built the whole package yet.

Ah, now I've gotten down to the end of my notes. I think I'm starting to remember why I didn't put them up at the time:

While the evidence for bipedality in the earlier A. anamensis is not nearly so extensive as that in A. afarensis, nevertheless it is quite compelling, particularly the KNM-KP 29285 tibia. You'd get pretty long odds betting that the Mille pelvic bones looked very different from Lucy's. I have no information about the pelvis at all, certainly no photos, but it would indeed be a surprise for it to be outside the A. afarensis-A. africanus range of variation.

But then, all it would take is one funky-looking pelvis to throw the whole question of pre-4.0-million-year-old hominids wide open. So maybe we should hope that it's strange.

Well, we certainly got one funky-looking pelvis, didn't we? I'm beginning to think I should republish old notes more often. What are the chances that another funky pelvis is waiting to be published?

Could it be that Woranso-Mille could represent an intermediate postcranial form at 3.7 million years? That would be one good reason to nail down the question of anagenesis from the craniodental perspective.

I think we may already have a hint at the answer. It's a little hard to imagine that Haile-Selassie and colleagues would propose sinking A. anamensis if they already knew that their skeleton has a different postcranial anatomy than represented at Hadar.

There's one more thing worth mentioning: this paper doesn't include any discussion, comparison -- it doesn't even breathe the name -- of the other 3.5-million-year-old hominin. It's not just a skull; there is a sample of teeth from that unmentioned site, which of course may or may not represent the same taxon. Like a forgotten stepchild of paleoanthropology. Is it possible that peer reviewers have already forgotten it's existence?

When I wrote about what I'm wondering, well, this isn't the only paper to have recently omitted this obvious comparison. I'll have more on that little problem later on...

References:

Haile-Selassie Y, Saylor BZ, Deino A, Alene M, Latimer BM. 2010. New hominid fossils from Woranso-Mille (Central Afar, Ethiopia) and taxonomy of early Australopithecus. Am J Phys Anthropol (in press) doi:10.1002/ajpa.21159

Kimbel WH, Lockwood CA, Ward CV, Leakey MG, Rak Y, Johanson DC. 2006. Was Australopithecus anamensis ancestral to A. afarensis? A case of anagenesis in the hominin fossil record. J Hum Evol 51:134-152. doi:10.1016/j.jhevol.2006.02.003

Just noticing, in this John Noble Wilford article:

A new report, to be published Thursday in Nature, will review more skeletal evidence of the transitional aspects of the Dmanisi specimens.

More later...

UPDATE(2007/09/18): Wilford doesn't directly state the article's theme but it clearly has one: Why the heck can't these people agree about these fossils that have been out of the ground for thirty years?

The first answer that everyone has given him is about the "million year gap" between 3 million and 2 million years ago. People can't agree about early Homo because they can't decide what its ancestors looked like. Without any ancestors, they don't know which of the traits of early Homo are derived.

For a good example, we can turn to a feature Wilford doesn't mention: limb proportions. Recently, a lot of ink has been spilled discussing the evolution of arm size in later australopithecines and early Homo. OH 62 (probably Homo habilis) and A. africanus have been argued to have large arms compared to their legs. A. afarensis and Nariokotome (KNM-WT 15000, probably Homo erectus) have relatively small arms compared to their legs. Did H. habilis and H. erectus have different ancestors? Did H. erectus evolve from H. habilis, reverting its limb proportions to earlier A. afarensis? Or are all these comparisons just batty, since only three specimens have arm and leg elements whose length can be compared? There's no clear answer; but one of the most important specimens in the question (with sort-of-intermediate limb proportions) is the Bouri skeleton, BOU-VP 12/1, which at 2.5 million years old is right in the middle of that "gap."

The more you look at the "gap," the less gap-like it looks. For one thing, we have a pretty good idea of what was going on behaviorally during that million year span. The first stone tools are 2.6 million years old. The technology of these toolmakers -- although simple -- included all the basic manufacturing methods used before 1.5 million years ago. The tools were used to butcher animals and break bones for marrow; so we know that the toolmakers were depending on meat.

Second, we actually have quite a lot of fossils from this time period. The entire South African A. africanus fossil record, with the exception of a few early specimens like STW 573, come from this "gap." A fairly extensive record of the appearance and evolution of early robust australopithecines comes from this time period in East Africa.

And, here and there, a few specimens look Homo-like. Wilford's article discusses AL 666-1. To this we can add the Uraha mandible, Omo 75-14, an additional series of teeth from Omo, and possibly the Bouri BOU-VP 35/1 skeleton.

Properly considered, the rarity of early Homo in these contexts is not a problem; it is information. Wilford quotes Philip Rightmire to this effect, and we can easily expand on the basic concept. Early toolmakers did not undergo an immediate geographic expansion upon their origin. They spread across a relatively narrow strip of East Africa and stayed there for more than a half-million years. They were initially rare. That means that their adaptation was not immediately a barnburner of a success -- the early toolmakers took a while to perfect the adaptation of later Homo.

The middle part of the article takes in another reason for disagreement: whether H. habilis and H. erectus were ancestor-descendant:

Several scientists, notably Dr. White of Berkeley, took issue with the interpretation seeming to imply that evidence for the two species overlapping in time and exhibiting variable sizes was new. That, he said, had been recognized for a couple of decades.

Dr. Kimbel, who was not involved in the new research, defended the authors, saying that they had not "meant to imply that habilis could not have been ancestral to erectus, presumably on the basis of their being contemporaneous at Turkana," the site in Kenya where the fossils were found.

Susan C. Anton, an anthropologist at New York University who was a member of the Spoor-Leakey team, said, "My money is still on habilis as the potential ancestor, but there is a lot of room for additional knowledge, given the dearth of fossils."

None of these statements really disagree with each other. If anything, this particular question may have gotten easier to resolve lately, not as a consequence of new fossils, but as a result of new dates for many of the old ones. Susan Anton is later quoted saying that anagenesis "is the only option that is no longer on the table," and it seems to me that this is the clearest statement most likely to invite some hypothesis testing. But it is fairly clear that this problem cannot be resolved in terms of earlier fossils: I don't think there's any compelling evidence of H. erectus before 1.6 million years ago.

There is one significant word that doesn't appear in the article -- an absence that is especially interesting considering the quoted scientists:

Kenyanthropus

Remember, the dominant theme is about complexity and bushiness. And yet, here's that forgotten branch of the family tree; the one that was supposed to clarify everything by providing a different ancestor for KNM-ER 1470 from other H. habilis specimens, the one that showed a distinct line leading to Homo originating in the Early Pliocene.

I think our bush may have been pruned.

I'm about two-thirds of the way through Mike Morwood's new book, The Discovery of the Hobbit, and I'll be posting a review when I'm through. Generally, I have a positive opinion of the book so far.

Henry Gee has reviewed the book in this week's issue of Nature. I wanted to point out my generally positive attitude about the book, so that you'll know that my miserable opinion of Gee's review has little to do with the book's merits.

Consider how Gee starts his review:

The unicorn, wrote Jorge Luis Borges (in Kafka and His Precursors), is universally regarded as a supernatural being of good omen. But there's a problem: despite its folkloric familiarity, we wouldn't know how to recognize a unicorn if we met one in real life. It "does not figure among the domestic beasts, it is not always easy to find, it does not lend itself to classification," Borges continues. "It is not like the horse or the bull, the wolf or the deer. In such conditions, we could be face to face with a unicorn and not know for certain what it was."

Is Gee smoking crack? What kind of blather is this?

First of all, I know I'm being terribly literal, but a unicorn is a horse with a horn. One horn. Not so hard to recognize! Maybe my 3-year-old daughters could help edit at Nature.

Let's see, where have I seen one of those that Gee might recognize? Oh, yeah:

Photo credit: Simon Stratford (via stock.xchng)

There it is, sound as a pound.

Next, Gee spends several paragraphs expositing on his own role in the publication of the Homo floresiensis announcement. We learn some interesting little facts, like how the authors wanted to name the species "Sundanthropus floresianus" until a reviewer pointed out that future students would confuse the name with a flowery butt.

I kid you not. Nature has a layer of reviewers to take tushie references out of taxonomy. Somehow they can't tell a left femur from a right, but they're on the watch for sphincter-species!

The review is entirely self-serving -- there are only three paragraphs that include any reference to the book! In the midst of this babbling about unicorns and hobbits, Gee tells us that skepticism at new hominid discoveries should be dismissed as the predictable result of "mindsets" of the skeptics:

Such reaction is common in the wake of new hominid discoveries, which are routinely dismissed either as pathological humans (Homo neanderthalensis) or apes (Australopithecus africanus and Sahelanthropus tchadensis). Such reactions say less about the facts than the mindsets of commentators, who might be unwilling to have their comfortable views of the world so forcibly changed. Confronted with what might be a genuine unicorn, many would prefer to see a pantomime horse with a spike glued to its head.

Ooooh! Since I'm one who has been notably skeptical of Sahelanthropus and have approached H. floresiensis skeptically, I'm obviously a prime target for this paragraph. It is so comfortable to stay in my view of the world where hominids interbreed with each other. Clearly, a bestiary that includes small-brained island bipeds must shake me out of my comfort zone.

How could I have been so wrong! When every species ever proposed has faced the same resistance? Sure, Tim White says that Kenyanthropus is a glued-together matrix-filled A. afarensis, but that's just his mindset. Or how about Eoanthropus? Sure, Franz Weidenreich thought that it was just a concoction by "English authors," but couldn't he tell that it was more than just a pantomime skull with an orangutan jaw? Why couldn't I see that these petty minds were just holding back the important work of taxonomy!

No, no, no. You see, if we approach things skeptically, we won't dare to dream about the unicorns:

The unicorn remains as it always did, frustratingly elusive. This year, the researchers will return to Liang Bua to see if they can discover more. But stories such as this demand a mythological beast altogether less serene. It is as if the researchers had set out to discover some new form of fossil mouse, only to find that they had grabbed a dragon by the tail instead. And as any devotee of Harry Potter will remind you: Draco dormiens nunquam titillandus.

The theme of the review is perhaps to be expected from Gee, otherwise known as the author of The Science of Middle-Earth. But I find his mixture of fantasy and science to be especially malaprop in the context of the Flores fossils, since with every fantasy word he detracts from the credibility of the journal's review process!

Some of you will have seen the episode of The Simpsons, titled "Lisa the Skeptic," where Lisa excavates an "angel" from the ground. Here's part of the synopsis from Wikipedia:

As Homer attempts to get a motor boat, a new shopping mall in Springfield is being built on an area where a large number of fossils were found. Lisa condemns and protests the building of the mall. Thanks to her protest, it prompts the school to conduct an archaeological dig. When Lisa is digging, it reveals a human skeleton with wings. Springfield's residents are convinced it is an angel, and Homer cashes in by moving the skeleton into the family's garage; however, Lisa is skeptical, believing it may not actually be an angel, and even has Stephen Jay Gould test a sample of the skeleton. The next day, Dr Gould runs to the Simpson house and said the tests came out inconclusive and after Lisa on television compares belief in angels to belief in unicorns and leprechauns, Springfield's religious zealots riot and destroy all of the scientific institutions.

Later, we find out that the "angel" is a publicity stunt for the new mall; Guest voice Gould confesses that he never really performed any tests on the "angel". This is one of my favorite episodes: it's a rare one where Lisa's preachy skepticism is entirely justified, and the "expert" doesn't care enough to do anything at all.

Now I know, that the episode was missing a scientific editor to encourage Lisa to forget about her doubts, and just to accept the "angel" for what it is. After all, every new discovery has its skeptics.

Well, there is a lesson to take away from all the unicorn talk. If you are in Cardiff and find the skeleton of a giant, be sure to send your report to Nature, where you'll find a receptive editor. Despite what they may say, there's not one of those born every minute.

UPDATE (4/26/2007): A reader e-mails, "Remember that Borges was blind." True. Perhaps we can extend this analogy further?

Another reader: "Well, at least we can expect a fair set of reviews on the Sahelanthropus postcrania...D'oh!"

References:

Gee H. 2007. In a hole in the ground.... Nature 446:979-980. doi:10.1038/446979a