Microscopic barley grains. Top row are examples of grains from Shanidar calculus, and beneath each are examples of modern barley to which they are probably related. Fig. 1 from Henry et al. (in press)
Earlier this year, I discussed the publication of a mitochondrial DNA study from a 50,000 year old pinky bone from Denisova in Siberia. The big story there was that the mtDNA of this specimen was twice as divergent (different) from modern humans as Neandertal mtDNA. This suggested to researchers that there was this rogue human group (some [not I] might say ‘species’) running around Eurasia around the time of the Upper Paleolithic.
“It is fascinating to see direct evidence that these archaic species did exist (alongside us) and it’s only for the last few tens of thousands of years that is unique in our history that we are alone on this planet and we have no close relatives with us anymore.”
A paper just came out in PNAS, by Tanya Smith and others, in which they estimate tooth-crown formation times in a large sample of modern humans (n=>300 individuals), a modest sample of Neandertals (n=8), and a poor sample of ‘fossil Homo sapiens‘ (n=3). Teeth form by the periodic deposition of enamel (the hard, white part visible in teeth in the mouth) and dentin (forms the tooth root and internal part of the crown). These periodicities are fairly regular (though variable), thus allowing researchers to estimate how long it took for teeth to develop. As previous studies have shown, Smith and colleagues find that Neandertals formed most of their teeth faster than modern humans.
- SPAG17 is associated with sperm motility – is this evidence for sperm competition and recent sexual selection?
- Regions in which, among modern humans, mutations are associated with social-cognitive diseases like schizophrenia and autism
- RUNX2, again where misexpression in humans is associated with dysgenesis of frontal bone (forehead), shoulder and rib-cage shape morphology
Johannes Krause and colleagues reported yesterday in Nature‘s advance online publication, on a new hominin mitochondrial DNA (mtDNA) genome. The genetic material is derived from a finger bone which lacks diagnostic morphology, from a southern Siberian site called Denisova dating to between 30 – 50 thousand years ago. Of note, the authors describe that the mtDNA is about twice as different from humans as any neandertal mtDNA is from modern humans. If the human-neandertal mtDNA divergence is accurately estimated at around 450 thousand years ago, that means this mystery specimen’s mtDNA lineage diverged from the human-neandertal line around 1 million years ago.
Yesterday, two articles of interest to anthropologists were published in the the journal Nature‘s advance online publication. First is the announcement of a very complete bone flute, and fragments of other flutes, dating to around 35,000 thousand years ago from Germany. The finds come from the site of Hohle Fels in Southern Germany; a few months ago it was announced that the site produced the earliest Venus figurine. Venus figurines are some of the earliest pieces of carved art produced by humans, and are figures of corpulent women with corpulent lady-parts. This latter fact captures the popular imagination as the earliest ‘porn,’ but in truth no one’s sure what exactly they mean, although many researchers think they’re related to fertility. Anyway, the flutes are found in Aurignacian deposits, which by and large are attributed to ‘anatomically modern’ humans, as opposed to the contemporaneous Neandertals. The final sentences of the paper sum things up nicely:
“…early Upper Paleolithic music could have contributed to the maitenance of larger social networks, and thereby may have helped facilitate the demographic and territorial expansion of modern humans relative to culturally more conservative and demographically more isolated Neanderthal populations.”
I like their use of “culturally more conservative” description of Neandertals, whereas in the past the phrasing probably would have been “culturally primitive” or “…less advanced.” “Conservative” is certainly an interesting way to describe cultural differences between Neandertals and other Upper Paleolithic populations. I wonder if Neandertals were also more God-fearing and homophobic, as I understand ‘conservative’ to mean nowadays…
The second topic will have to wait. I just got invited to have dinner and drinks and watch soccer, which I’d be silly to pass up. Go South Africa!
News: Weaver and Hublin (2009) virtually reconstructed the Tabūn C1 female Neandertal pelvis using CT scans.
Background: This is the closest we have to a complete female Neandertal pelvis, so a lot of the discussion centers around obstetrics. When a modern human woman gives birth, the infant enters the birth canal facing sideways so that the head will fit through the transversely oval inlet, then turns 90 degrees so it is facing the back so that the head will fit through the AP oval midplane and outlet, and finally turns another 90 degrees after the head passes through the outlet so that the shoulders can also fit through the outlet.
Tabūn conclusions: Neandertal infants (based on Tabūn’s inlet, midplane, and outlet diameters) only required two rotations: the initial turn so the head faces laterally, and the last turn so the shoulders fit through the transversely oval outlet. This means the infant comes out with the head facing sideways and the shoulders facing front (this is also how australopithecines are thought to give birth). This, the authors suggest, means that Neandertals were more primitive than modern humans. Furthermore, the transversely oval birth canal reflects the cold-adapted wide pelvis associated with Neandertals.
- Methods: There is no sacrum for Tabun. None. It is possible to predict sacral width and thus reconstruct the inlet, but it is improbable for the outlet to be reconstructed accurately without knowing the sacrum’s length, curvature, and orientation.
- Sexual dimorphism: They confuse this throughout the paper. First, they female-ize Kebara (a complete male Neandertal pelvis) by assuming that Neandertals were as sexually dimorphic as modern humans. This has been shown to be wrong previously, so it was a dumb assumption. They also find that this is not the case, making me wonder why they bothered with it in the first place. Then, they claim that the difference between Neandertals and modern humans is that Neandertals are like modern males (who have short pubic rami) when really they’re like modern females (who have long pubic rami). See Rosenberg (2007) for more discussion of this.
- Cold- and warm-adaptations: They say that Neandertals were cold-adapted because of the wide birth canal, in contrast to warm-adapted modern humans from Africa. First, wide birth canals do not go hand-in-hand with wide pelves. Second, Tabūn lived in the Levant and thus did not need to be cold-adapted. Third, the Busidima female Homo erectus pelvis from Gona is also wide and also not cold-adapted. Fourth, modern humans in Africa evolved a narrow pelvis to be better adapted to the warm environment is based on… uh… KNM-WT 15000? No, wait, that’s also a H erectus, and Gona has already shown that they have wide pelves despite their climate. But what else is there to support this long-held idea? Answer: Not much.
- Weaver, TD and JJ Hublin (2009) Neandertal birth canal shape and the evolution of human childbirth. PNAS Early Edition: 1-6.
- Rosenberg, KR (2007) Neandertal Pelvic Remains From Krapina: Peculiar or Primitive? Periodicum Biologorum 109(4).