Anthropology.net

Despite the fact that I’ve seen some really impactful primate related research lately, I’ve completely neglected updating Primatology.net with it. I can’t believe it has been almost three months since I’ve posted there! I should really resume posting there. Actually, I was considering putting up this following blog post over there, since it has to do with differences in neuroanatomy of the primate brain… but because these comparative studies are in the context of identifying specific architectural differences in the human brain related to language, I think posting it here is more fitting.

If you’re a reader of Neurophilosophy, you may have an idea of what research I’m referring too, the new Nature Neuroscience paper from James Rilling and team. Before I jump into this paper, “The evolution of the arcuate fasciculus revealed with comparative DTI,” please let me share another recent paper that gives some introduction about what I’m gonna talk about.

See earlier this month, Current Biology published a paper, “Communicative Signaling Activates ‘Broca’s’ Homolog in Chimpanzees,” where researchers not only confirmed that the Broca’s area as an important area of the human brain for language comprehension, but also chimpanzees have similar activity in the homologous area of their brains when communicative signals are produced or heard. The Broca’s area has long been thought to be one of the specialized functional areas of the brain for language comprehension. In fact was discovered almost 150 years ago by a physician named Pierre Paul Broca, who conducted an autopsy of patient with a speech deficit. Broca was able to determine the patient had a syphilitic lesion in the left cerebral hemisphere and identified this area as his namesake.

If you’ve heard anything about Broca’s area, it larger in the left hemisphere of the brain. Comparing activity levels between the two hemisphere, during language-related tasks, have shown the left hemisphere Broca’s area is more active. That’s due to the lateralization of the brain, which I’m sure you’ve heard of.

Anyways, the results of this study have important implications in figuring out the functional and structural differences of the human and chimpanzee brain. Why? Well, for starters, the linguistic abilities of humans have been thought to be unique to us for a while. This is a really big misconception because research on signing apes and other communicating animals, have begun to show us that we’re not alone in our abilities to symbolize information and exchange it by way of complex sound and gesture.

In order to investigate the differences of the activity between Broca’s areas in humans and related structure in chimpanzees, Taglialatela et al., put three chimpanzee subjects in PET and fMRI machines and stimulated to vocalize by putting treats just out of their reach. They then recorded the activity of the subjects would vocalize in frustration. They were able to see the very same the neuroanatomical structures associated with the production of communicative behaviors in humans, fire in chimpanzees.

Now, of course that doesn’t mean chimpanzees are gonna be reciting Shakespeare anytime soon. This leads me to the first paper I mentioned today, the one from Rilling and crew. Rilling et al., did a comparative anatomical study on the structure of arcuate fasciculus, a large white matter tract, in humans, chimpanzees and macaques. The arcuate fasciculus functions as a linker between Broca’s area and another language associated area of the brain, Wernicke’s area. The researchers used diffusion tensor imaging (DTI), a type of noninvasive medical imaging that’s a lot like MRI but it compares and contrasts the local characteristics of water diffusion within tissues.

While the arcuate fasiculus of the rhesus macaque, the chimpanzee, and the human linked up to the frontal cortex — including with Broca’s area, it was observed that the human arcuate fasiculus is much larger. It more spreads deep into the middle temporal lobe, leaving the classical Wernicke’s area. In chimps, the arcuate fasciculus made very superficial connections to the temporal cortex regions homologous to Wernicke’s area. Macaques showed a much lower extend of this integration. Rilling commented,

“We know from previous functional imaging studies that the middle temporal lobe is involved with analyzing the meanings of words. In humans, it seems the brain not only evolved larger language regions but also a network of fibers to connect those regions, which supports humans’ superior language capabilities.”

This following diagram was published in Rilling et al.’s paper and illustrates their results:

So from these two papers, the evolution of specialized language areas maybe active in both chimpanzee and human brains but as the human brain diverged from other primate counterparts, major re-wiring at the arcuate fasciculus accompanied the massive expansion of brain size. Ultimately the area that is associated with understanding word meaning, Wernicke’s area, has been strongly connected with Broca’s area.

Rilling, J.K., Glasser, M.F., Preuss, T.M., Ma, X., Zhao, T., Hu, X., Behrens, T.E. (2008). The evolution of the arcuate fasciculus revealed with comparative DTI. Nature Neuroscience DOI: 10.1038/nn2072

TAGLIALATELA, J., RUSSELL, J., SCHAEFFER, J., HOPKINS, W. (2008). Communicative Signaling Activates ‘Broca’s’ Homolog in Chimpanzees. Current Biology, 18(5), 343-348. DOI: 10.1016/j.cub.2008.01.049

Tomorrow’s issue of the Science will host a reinvestigation of the famous (or infamous?) Orrorin tugenensis. The study, “Orrorin tugenensis Femoral Morphology and the Evolution of Hominin Bipedalism,” comes from William Jungers and Brian Richmond. Their shtick is that their results indicate Orrorin’s bipedality was like that of early Australopithecus.

This conclusion, albeit not too novel, directly challenges Brigitte Senut et al., who published the anouncement of Orrorin tugenensis in 2001. In that paper, “First hominid from the Miocene (Lukeino Formation, Kenya),” Senut and crew lay the foundation that Orrorin is an ancestor of modern humans because proximal femur is really different from Lucy’s, and the overall proportions of the head of the femur to the shaft resemble that of humans and not other early human ancestors. Orrorin is really old, like 6 million years old.

Of course, that was an outrageous claim. No one really doubted the bipedality… But looking at the bone, it really looked like Australopithecus. It was the same size as a chimpanzees too. Femora of Homo are longer. Furthermore, the other associated Orrorin fossils, like the canines, were like chimpanzees. So it is no surprise she got a lot of flak from people. It reeked of bias, as if Senut had this idea that there’s no way Australopithecus coulda been ancestral to humans and the first fossil she found that showed otherwise would be her cash cow. She even named it after the Tugen word for “original man.”

Criticism flocked, and Senut dug herself in a deeper hole when she was a part of the team that analyzed the internal morphology of one of the Orrorin femora with computed tomography (CT). I remember reading the 2004 paper, “External and Internal Morphology of the BAR 1002’00 Orrorin tugenensis Femur.” According to this paper, the CT scans of BAR 1002’00 revealed that the top of neck of the femur was thinner than the bottom of the neck of the femur. This indicates more structural integrity on the bottom, where gravity would most affect a bipedal organism. This trait, “approached the condition in later hominids.”

This fancy CT study didn’t do much convincing. The most prominent critique came from Ohman et al., who slammed Senut for originally gluing the fractured fossil right at the very position where one coulda made an accurate analysis of the cortical thickness without having to do crazy high tech obfuscation. Ohman and crew also argued that the fossilization process thickened the cortices, and that a simple X-ray woulda been more informative than very pixelated CT images. The response to Ohman et al. was pitifully, resorting whining. Everything remained quiet for about three years. Sunet and Pickford as well as some Japanese colleagues published a paper investigating body mass, and stature estimates of Orrorin last year. But it didn’t make that much of a buzz.

So in summary, it is agreed by many that Orrorin was bipedal, but just the degree it diverged in relation to other early hominids hasn’t widely accepted. Unfortunate for Senut, that was just one lemon she couldn’t hustle.

Fast forward to today, where Jungers and Richmond say their findings indicate that the Orrorin belongs to very early human ancestors, and that upright walking is one of the first human characteristics to appear in our lineage, right after the split between human and chimpanzee lineages.

How they went about doing it was by a multivariate analysis of measurement from the outside of the femur. The outside folks. Where would there be the most restructuring of femur for bipedalism? On the outside of the femur or on the inside? Think about it for a second… If you’re still confused a bit, just ask a structural engineer, the thickness of a hallow structure would need to increase as it bears more weight. As early humans became more bipedal, more weight was distributed on the femora compared to quadrupedal locomotion, where weight is distributed between four limbs.

That being said, I’m really curious to read just what they found about the measurements of the outside of the Orrorin femur. Why didn’t they just do an X-ray? A simple 2 view X-ray costs $250 or so.

One last thing, this National Geographic News article quotes Ian Tattersall, curator of the division of anthropology at the American Museum of Natural History, saying,

“If you were going to predict what an early hominid would look like six million years ago, you’d say [it looks] much more like the Australopithicines than like Homo… “

Seems like Tattersall is flipping the stance he took on Orrorin‘s place in the ancestry of humans. In 2oo2, he’s quoted in an Ann Gibbon’s piece, “In Search of the First Hominids,”

“As a working hypothesis, I think [Senut et al.] are correct, although they don’t have the most diagnostic set of fragments.”

Galik, K. (2004). External and Internal Morphology of the BAR 1002’00 Orrorin tugenensis Femur. Science, 305(5689), 1450-1453. DOI: 10.1126/science.1098807

Gibbons, A. (2002). BECOMING HUMAN: In Search of the First Hominids. Science, 295(5558), 1214-1219. DOI: 10.1126/science.295.5558.1214

Nakatsukasa, M., Pickford, M., Egi, N., Senut, B. (2007). Femur length, body mass, and stature estimates of Orrorin tugenensis, a 6-Ma hominid from Kenya. Primates, 48(3), 171-178. DOI: 10.1007/s10329-007-0040-7

Ohman, J.C. (2005). Questions About Orrorin Femur. Science, 307(5711), 845b-845b. DOI: 10.1126/science.307.5711.845b

Senut, B. (2001). First hominid from the Miocene (Lukeino Formation, Kenya)Premier hominidé du Miocène (formation de Lukeino, Kenya).. Comptes Rendus de l’Académie des Sciences – Series IIA – Earth and Planetary Science, 332(2), 137-144. DOI: 10.1016/S1251-8050(01)01529-4

Do we really need to consider turning everything upside down by considering the existence of a human ancestor for the apes? This suggestion definitely has the quality of blasphemy against religious doctrine. It just feels wrong and goes against our deeply held beliefs and understanding of the world.

However, this is exactly where the evidence leads.

Overall, I don’t expect that the entire anthropology community will suddenly abandon everything that has been taught for decades. However, my point is the following:

1. We see the spine anatomy of a hindlimb supported upright ape in Morotopithecus, Pierolapithecus, Oreopithecus. The data is compelling and extensive – and I have detailed it in technical raw data form in my book: Axial Character Seriation in Mammals, which republishes my Harvard PhD Thesis. The underlying patterns are extracted and synthesized in my recent PLoS ONE paper “Homeotic Evolution of the Mammals, Diversification of Therian Axial Seriation and a Morphogenetic Basis for Human Origins” and in my Neurosurgical Focus article. The context in evolutionary theory is explained in my recent book “The Upright Ape: A New Origin of the Species” which has a foreword by David Pilbeam – currently Dean of Harvard College and certainly one the most knowledgeable and experienced paleoanthropologists in the world.
2. We have evidence of an upright hindlimb supported Orrorin based on the femur and Sahelanthropus based on the skull.
3. There is no convincing fossil evidence at all of a non-bipdeal hominoid outside of the proconsulid group.
4. We have an early outgroup whose infants have innate bipedal walking (see the video Hominiform Progression). The Siamang video is interesting because of the innate bipedalism. As I point out in the video, John Fleagle has seen young siamangs of this age walk bipedally high in the canopy in Malaysia.

It is typical to say that all of this is irrelevant and misleading and should be ignored. There was a quadrupedal common ancestor for chimps and humans and the human lineage suddenly and majestically stood up about 5-6 million years ago. However, I feel that there is no a priori reason why we must ignore all of the evidence for early bipedalism.
None of the skeletal evidence can ultimately distinguish between “short bursts” and long distance bipedalism as Kambiz points out in his post. My focus is on the character state and whether the crucial anatomical basis is a shared derived feature of a hominiform clade.

It can certainly be said that the siamangs only engage in bipedalism for short bursts, but that is also true of their brachiation. Similarly, the chimps and gorillas knuckle walk and the orangutans fist walk only in short bursts. However, the important point is that chimps, gorillas and orangutans seem to locomote in diagonal posture more than 90% of the time and only occasionally deploy a short burst of bipedal walking. I would argue that they have very bad spinal architecture for bipedal walking. On the other hand, hylobatids use bipedalism 100% of the time when they locomote on the ground no matter how long the burst of activity. If a hylobatid has to travel a long distance on the ground – it does not lapse into a quadurpedal gait – it just keeps walking bipedally. There is an important difference in the role of bipedalism as deployed by hylobatids and hominines as opposed to what we see in chimps, gorillas and orangutans.

This would be a morphogenetic origin for upright bipedal walking rather than an adaptive origin. Essentially, the origin of upright posture was not driven by any ecological scenario, but rather occurred suddenly as a result of a morphogenetic mutation in the Pax genes. Various descendant forms will have lived in various environments with variously optimized versions of primary upright bipedalism on large horizontal arboreal supports and on the ground.

It is certainly easier to assert that Morotopithecus was upright and hindlimb supported – based on spinal anatomy – than to prove it was primarily bipedal or a long distance walker. However, this is where the video showing the baby siamang learning to walk bipedally is relevant. Yes, you could argue that innate bipedalism evolved independently in parallel in hylobatids and hominines, but is also reasonable to consider that since this is so unusual, that it reflects descent from a common ancestor that had this feature. Essentially – an eight month old Morotopithecus baby would do the same thing that we see in the two descendant groups (hominines and hylobatids) – the baby would innately begin to walk bipedally as it’s primary locomotor pattern.

So – if the chimp-human split did take place 6 million years ago (as the molecular data suggests), then what do we do with Sahelanthropus which many believe was a full time upright biped but which lived 7 million years ago?

If you want a slow gradual evolution of bipedalism, you need to push the chimp human split back to say 8 million years. However, there is an alternative explanation. Upright bipedalism was already the primary means of locomotion in the common ancestor of chimps and humans – Sahelanthropus is ancestral to both lines.

What defines a “human?” I have taken the position that it is a body plan (bauplan). Most of us have accepted that early Australopithecines whose brains and skulls were chimp-like, should be considered human and not ape. When you find a fossil such as Sahelanthropus that has a “chimp-like” skull from the point of view of its face and brain, but has the skull base of a human (and presumably upright bipedal post-cranial anatomy) – how can you tell from the fossil if it’s an ape or a human?

The Hennigian cladistic approach lets us say that the isolation point between the chimp and human lineages – where hybridization became impossible – is the origin point of humans. However this means that the definition is arbitrary since ape and human would pretty much look identical at that time.

Another alternative is to stick with our current definition – a hominoid whose anatomy reveals that it is primarily an upright biped is a human. I have proposed the term “hominiform” to refer to a clade of hominoids that share the Morotopithecus spinal transformation (septo-neural transposition – in which the dorso-ventral plane of the body flips from ventral to the spinal canal to a new position dorsal to the spinal canal) and the styloid process is converted into a neomorphic hominiform lumbar transverse process. The synapomorphies would include innate bipedal walking in the infants.

Among hominiforms we have primitive “eubipedal” types (most Miocene and Pliocene fossil hominiforms, the hylobatids and the hominines) and derived “metabipedal” types (lineages of chimps, gorillas and orangutans) that have abandoned bipedalism as their primary locomotor pattern on the ground.

Sahelanthropus appears to be a human species that is representative of species in the line of ancestry to both the chimpanzees and hominines.

Aaron Filler, MD, PhD

I have been really anticipating the following study. The first press releases came out in March and in October, I introduced it here. It seems like the paper is finally ready to be published, but we still gotta wait until PNAS puts it up on their early edition section. It should be soon but I really can’t wait any more! It is almost torturous how PNAS teases us with press releases for such a long time prior to the actual publication being released. So in the mean time, I’m gonna have to make you suffer thru an extension of my October introduction.

The study ultimately originates from Jean-Jacques Hublin, director of the Human Evolution Department at Max Planck Institute for Evolutionary Anthropology in Leipzig. But the team of co-authors are an international group who studied growth patterns in Neandertal teeth. Similar to the rings around a tree are these unique growth lines both inside and on the surfaces of teeth that can be counted to estimate age and developmental stage at death. This form of tooth analysis is called dental anthropology.

As an undergraduate, I was friends with several graduate students at my anthropology department were studying this aspect of physical anthropology. My friend Josh studied animal teeth, specifically deer teeth, from archaeological sites to estimate the time of year that hunting took place. If I remember correctly, Vicki Wedel and Chelsey Juarez have also both used this form of analysis to estimate the age of human remains found in a forensic context.

The new study applies dental anthropology in a paleoanthropological context; Neandertals were analyzed to study their growth developmental patterns in comparison to humans. In October, only four hominids were reported in the analysis the Nean dertals from Le Moustier and Krapina and the early Homo sapiens from Qafzeh and Jebel Irhoud. In a press release issued today, the Scladina Neandertal child is also included in the study.

Here’s an excerpt of the most important result so far,

“The Scladina juvenile, which appears to be developmentally similar to a 10-12 year old human, was estimated to be in fact about 8 years old at death… The Scladina Neanderthal grew teeth over a shorter period of time, and has more teeth erupted… than similarly-aged fossil or living humans (Homo sapiens). This suggests that other aspects of physical development were likely more rapidly achieved as well, implying significant differences in the behaviour or social organization of these ancient humans. This pattern of development appears to be intermediate between early members of our genus (e.g., Homo erectus) and living people, suggesting that the characteristically slow development and long childhood is a recent condition unique to our own species.”

So Neandertal growth and development was much more accelerated than modern day humans. Very interesting conclusion. The following two tables document standard patterns of tooth development in modern humans, they were reconstructed from pages 32, 45, and 53 of Ash & Nelson, Wheeler’s Dental Anatomy, Physiology, and Occlusion. Note, this is not a fixed pattern for all humans, but rather a compilation of average times of tooth development. For example, my third molars (wisdom) teeth were completely developed and erupting when I just turned 14. This table says the norm for wisdom tooth eruption is 17-21 years of age.

So clearly my developmental pattern was ahead of the game as far as my wisdom teeth goes. What if that was the case then for this Scladina Neandertal? What if it was like me and developed its teeth faster? This here in lies the problem with limited samples. Sure, I don’t yet have the publication to see exactly how large the sample size was, but without large numbers (n = to 100 or larger) it is hard to get an accurate representation on what’s the normal accepted values for tooth variation. I know there ain’t that many juvenile Neandertal fossils as of yet.

If Neandertals were anything like us, and the genetic, archaeological, and skeletal evidence shows they were more similar than not, surely they a lot of variation that would affect the rates of development and life history… Just something to think about before the paper comes out.

One last thing, here’s the running title and citation to the paper,

“Rapid Dental Development in a Middle Paleolithic Belgian Neanderthal”
Tanya M. Smith, Michel Toussaint, Donald J. Reid, Anthony J. Olejniczak, Jean-Jacques Hublin
Proceedings of the National Academy of Sciences USA December 2007

This week, we saw a short paper in Science on Paranthropus robustus sexual dimorphism and the implications the differences between sexes had on this early hominid social behavior. Here’s the title and a link to the original publication, “Extended Male Growth in a Fossil Hominin Species.”

Sexual dimporphism is what scientists use to define the differences between male and female body sizes and anatomical variation. In great apes like gorillas and orangutans, there is a large degree of sexual dimporphism. Males are physically much larger, for example, some male silverback gorillas are twice the size of female gorillas. Male gorillas also have pronounced sagittal crests and other skeletal features that support larger bodies. Chimpanzees and bonobos do not exhibit sexual dimporhism to the degree gorillas and orangutans do. They fall more in line with humans. Most modern day human skeletons have finite differences that aren’t really cut and dry, but almost all male ape primates have two periods of growth and development during adolescence, one prior to females and one after female adolescence development wraps up. This is understood as an adaptation to complete growth after all the competition has passed its prime.

As the binomial name implies, the specimen analyzed in this last week’s issue of Science, Paranthropus robustus is a robust australopithecine. Robust means it has a lot of pronounced features, and this species makes for a great example to study robusticity because there’s a lot of Paranthropus fossils.

There is some really ignorant press that confused Paranthropus robustus as a human ancestor, such as this National Geographic News headline, “Early Human Ancestors May Have Had “Harem” Societies.” This headline is not particularly true. True, these australopithecines were bipedal and succeed after Australopithecus afarensis and africanus. A branch off of the Australopithecene lineage most likely gave rise to early Homo, but the current consensus among plaoeanthropology is that the Paranthropus lineage did not. Another separate australopithecine lineage gave rise to the Paranthropus genus.

Furthermore, all known P. robustus fossils are not older than 2 to 2.5 million years ago, which means they succeeded A. africanus and appeared after the Homo lineage already diverged. I’d like to clarify that not everything hominid is directly related to humans. For all we know now, we can only say that
the Paranthropus genusshared a commn ancestor with humans. So keep that in mind as I review this publication.

This study used 35 P. robustus specimens from Swartkranns, Kromdraai, and Drimolen sites in South Africa. Like I mentioned in the paragraph above, the deposits these fossils came out from are no older than 2 million years ago and no younger than 1.5 million years ago. The authors limited their pool of specimens to analyze into three criteria. The fossils had to show evidence that the last molar tooth had erupted. M3, the last molar, usually coincides with adolescence, a time during life history where sexual differences manifest while the primate undergoes puberty and sexual maturity. Other logistical criteria included having sufficient parts of the fossil fragments to make a complete analysis. Ultimately 19 face fragments, most of which came from Swartkrans and most of the 16 jaw fragments also from Swartkrans were studied. In the sample there were about 29 males and 6 females P. robustus represented, which they account for because males were less shielded from predation than females.

The amount of wear on each specimen’s teeth was studied to estimate the ages of the individuals at the time of death. The authors state that they had a sample that represented ‘nearly every stage of dental wear from young adulthood to old age.’ The authors make note of an observation that the P. robustus males exhibited a bimaturation pattern, and older males were much larger than the younger males.

They authors go onto infer how the differences in the pattern of development in P. robustus males and females represent gorillas and not really other australopithecines. The pressed loved this, eating it up and spitting it out to the public that early hominids had harems much like a male silverback does. I’m not too certain about that, it is a strong possibility that’s the case. The adaptionists understand this is an excellent reproductive and evolutionary strategy, larger the male the more he can dominate females as well as thwart out competition from other males. That’s how silverbacks do it, and other animals such as lions, elephant seals, etc.

But I’m not completely sold. I’m uncertain about this all because one of my undergraduate professors, Dr. Adrienne Zihlman, instilled a lot of uncertainty in me about sexual versus species differences, especially in australopithecines. She argued that lots of the robust australopithecines, such as P. robustus can represent only the males of the species while the gracile ones represent the females. Ultimately, she was saying what we maybe calling different species could be just the differences between males and females. If you ever seen male and female orangutan or gorilla skeletons, and didn’t know who was who, you could divide them up into 4 different species. For this reason, I’m not sold that P. robustus was harem like, I do agree that the authors made an astute observation that there is a bimaturation processes in the 29 of the specimens analyzed. That’s about all I feel comfortable with settling on.

I’ve been under the radar for several days.

I’ve been struggling to understand this paper, “Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphogenetic Basis of Human Origins,” from Aaron Filler of Harvard’s Anthropology department. All I can really make sense of it is that there’s a probability that bipedalism originated way earlier than we think right now. And that chimpanzees, gorillas, and the like, were mutants that reverted back to a more primitive primate body plan.

Filler suggests this because of a transformed hominiform type of lumbar spine found in Morotopithecus bishopi, an extinct hominoid species that lived in Uganda more than 21 million years ago. In the paper he compares human vertebra to the Morotopithecus, which both show an absence of the styloid process and relocation of the lumbar transverse process. Because of this transformation, he suggests Morotopithecus, along with three upright bipedal species from the Early Miocene, were bipedal long before any Australopithecine.

His analysis is very thorough but it is honestly hard to accept. If you wanna read more about Morotopithecus, you maybe interested in this, “Postcranial functional morphology of Morotopithecus bishopi, with implications for the evolution of modern ape locomotion.”

I’ve done so much flip flopping on whether or not Homo floresiensis is in fact a new species of human over the last 3 years that I sometimes forget what opinion I currently hold. The only consistency in my debate has been the call for analysis of the other remains. It seems like I got my wish after catching last week’s Science publication of the The Primitive Wrist of Homo floresiensis and Its Implications for Hominin Evolution. The title is pretty self-explanatory.

H. floresiensis is a hominin found in 2003 from the Ling Bau cave on the island of Flores in Indonesia. The bones found are about 18,000 years old. There’s been a lot of back and forth discussion whether or not H. floresiensis deserves a new species. At first people thought it was a representative of H. erectus, then it was suggested that H. floresiensis is a primitive microcephalic modern human. I like many others held this opinion.

Earlier this year, Dean Falk did a comparison of the endocranial volume of the H. floresiensis skull, LB1, to a number of microcephalic humans, and primates. She found H. floresiensis to be uniquely different in size and morphology. For many that wasn’t enough because, we don’t have many microcephalic human skulls to measure and compare too.

The other bones found at the site are just as diagnostic, especially the bones of the wrist and hand. So what Tocheri et al. did was to use fancy 3-D methods to calculate all the different dimensions, areas, and angles of the trapezoid, scaphoid, and capitate bones and multivariate statistics were used to compare the Flores carpal bones to set of archaic and modern humans, Neandertals, australopithecines, gorillas, chimpanzees, and also OH 7 a.k.a. Olduvai Hominid № 7 or the type specimen for H. habilis. Here’s a quick run down on what they found.

The trapezoid is the main bone where the index finger’s metacarpal articulates with the rest of the wrist. It’s a small bone in modern humans. The Flores trapezoid is wedge shaped like humans but has a different orientation on the ulnar side. Here’s the figure they showed which illustrates LB1, Flores trapezoids, compared to the others.

The Flores scaphoid shape and articular surfaces are more triangular in shape and lacks the larger articular surface on the palmar side which is seen in modern humans and Neandertals. Curiously, the scaphoid also has a fused centrale; a condition seen in H. habilis.

The authors say this fusion is a primitive condition for all hominins, because in modern humans it is separate. But that is not entirely true. The centrale sometimes fuses onto the scaphoid as the tubercle of the scaphoid; but occasionally it stays separate. It is not as definitive as they authors are making it out to be.

Anyways, here’s the line up of the scaphoid comparison.

Last but not least, is the sweet capitate. The capitate is the largest bone in the wrist and it falls smack dab in the center. Aside from the size, I remember the capitate because it has a rounded head which reminds me of Captain Picard’s bald head. And no, I’m not a Star Trek fan… it just that this bone has a remarkable resemblance to his unforgettable head.

Parts of the capitate, like the head, look like a chimpanzee’s capitate. Check out the light blue part below. But others, such as the proximal surface (green part) resemble modern humans. All in all the authors say the articular facets and shapes are more primitive than not because of a “waisted neck” characteristic that I don’t know about.

Can you see it?

I must admit they have a pretty complete line up of capitates, and the images let us all see for ourselves how these three bones compare…

…But I wonder why they didn’t include microcephalic or even dwarf humans into the mix?

That’s my biggest complaint with this study. You’d think that they’d include them, considering the biggest competing hypothesis is the whether or not H. floresiensis was a bunch of small humans. I’ve never seen bones from a microcephalic’s or dwarf’s hand to say that their bones would be more primitive than not… but I would assume since dwarf skeletons are much more distorted they would have different morphological features.