Archaic Morphology and American Indian Biological Variability

On the heels of my last post about the possibly systematic trend to ignore American Indian samples in the studies of worldwide variation, there’s a new paper dealing with the discovery of human remains with archaic morphology as late as the early Holocene in East Asia. The authors dated Longlin and Maludong remains in South China and used a database of recent and ancient humans to identify their relative position in the universe of ancient and modern craniological variation. Longlin dated at 11,510±255 YBP, while Maludong at  14,310 YBP to 13,590 YBP. They concluded that these skulls are unusual for East Asia in showing a mosaic of archaic and modern features.

For some inexplicable reason, although the recent human sample came from Howells, American Indian skulls were not included. The only time when a New World population, namely the Inuits, is referenced in the paper is when the authors compare Longlin and Maludong with Mongoloids. The specimens are decisively non-Mongoloid. Meanwhile, in the light of the reinterpretation of the earliest New World skulls as “non-Mongoloid” proposed by a number of scholars in the past 15 years (see, e.g., Joseph Powell’s The First Americans: Race, Evolution, and the Origin of Native Americans, 2005), it’s difficult to explain why American Indian skulls did not make the cut. This unfortunate neglect of American Indian samples replicates the common practice in population genetics. In the absence of American Indian skulls in the comparative set, it’s impossible to say how close Longlin and Maludong are to New World crania, but there are a couple of observations that can be made from what the authors published.

The authors identify the morphological features that set Longlin and Maludong apart from modern humans. Among them is supraorbital torus. The authors mention that supraorbital torus is very rare in recent human populations and becomes more frequent among Pleistocene humans. But it’s precisely among American Indians that we find examples of supraorbital torus. Marta Lahr (“Patterns of Modern Human Diversification: Implications for Amerindian Origins,” Yearbook of Physical Anthropology 38 (2005): 163-198) identified this feature in 8% of Fuegians. 57% of Fuegians in her sample had brow ridges. Paleoindian skulls such as Lagoa Santa and Jalisco also have well-developed ridges.

The Longling and Maludong didn’t preserve much of dentition (both specimens yielded dental crowns, Maludong also showed up a maxillary third molar). Just like  Neanderthals (and many Inuits), Longlin and Maludong are taurodonts. It would be great to have a look at their incisors but judging by the fact that shoveling is very frequent among both Neanderthals and Asian Homo erectus it wouldn’t come as a surprise if Longlin and Maludong had shovel-shaped incisors. And among modern human populations shoveling is most prominent among American Indians.

What is this telling us? First of all, archaeological and paleontological record is fragmentary and a “moving target.” Such recent discoveries as the Kennewick Man, the Denisova Cave remains, Homo floresiensis, the Zhirendong chin and, now, the Longlin and Maludong remains demonstrate that we can hardly be certain in the completeness of our knowledge of the past. Every decade brings new discoveries that just a few years ago would have been dismissed as “unlikely” by academic archaeologists and paleontologists. Short periods of stability in the “archaeological record” end in outbursts of paradigm-shifting discoveries. A whole new species of hominins, which was small and isolated but apparently contributed genes to modern humans, survived only in the form of a pinkie and a tooth (Denisova Cave). To reiterate what I wrote in an exchange with Greg Cochran, “ancient human remains shouldn’t be treated as a ‘record’ for humanity but rather as ‘paper’ onto which diachronic patterns derived from modern human populations should be inscribed.” Secondly, the paleobiological record in North Asia, East Asia and Southeast Asia is extremely fragmentary, poorly preserved, with uncertain dates. This makes inferences about the critical period in the formation of modern humans (100,000 YBP and later) very risky. But it’s noteworthy that a whole range of interesting and ground-breaking finds in the past 20 years came from Asia and America and not from Europe or Africa. And even when it came from Africa (e.g., Hofmeyr or Iwo Elleru) it also challenged the out-of-Africa theory. Thirdly, the paucity of human remains in the New World earlier than 12,000 YBP is just an extreme case of the fragmentary nature of the paleobiological record in Asia. It’s not an indicator of the absence of humans in the New World prior to 12,000 YBP, but the reflection of their demographic and adaptational specificity. The richness of the craniological material from Europe (and Africa) likely reflects greater human and hominin population size on those continents, while the sparseness of ancient crania in Asia and America probably reflects long-term low population density and high mobility of hominins and humans there. But it’s precisely in Asia, Papua New Guinea, Australia and America – regions with the highest levels linguistic diversity – that we can expect the preservation of dental and cranial archaisms in recent human populations. Fourthly, what we are seeing in Asia, Papua New Guinea, Australia and America is mounting evidence for biological variability that doesn’t fit with the serial bottleneck model of the peopling of the world from Africa. This is the conclusion of a paper by Sardi et al. “Amerindians: Testing the Hypothesis of Their Variability” (2004): South American Indians are not craniometrically homogeneous, even when geographically proximate populations are considered. From a genetic perspective, some of the roots of this variability clearly stem from Neanderthals and Denisovans, but it’s unclear whether these archaisms are product of gene flow or represent true common descent. Similarly, are archaisms found in African populations products of admixture with African archaics or traces of common descent from them?