Anthropology.net

If you’re a regular reader of Dienekes blog, you’d know he’s consistently raised concerns that calibrations of molecular clocks don’t quite fit the bill. Yesterday, he posted an addendum and shared a new paper in which authors advocate that molecular clock can be calibrated upon an archaeological context (not phylogeny-based) and human mtDNA estimates of dates of population and phylogenetic events should be adjusted to time-dependent mutation rate estimates.

I’m not gonna get into a rehashing of Dienekes’ post, I wouldn’t do as good of a job even if I did… but you should jump on over and read what he has to say and how he explains his criticisms of how the clock has been calibrated in the past. I want to spend some time in this post discussing some of the results of the paper he shared, “Characterizing the Time-Dependency of Human Mitochondrial DNA Mutation Rate Estimates,” in Molecular Biology and Evolution. The authors sought to establish genealogy-based estimates of the mtDNA mutation rate using both hypervariable and coding region data, they also wanted to figure out if multiple hits  affect the discrepancy between the different methods of mutation rate estimation.

So they setup new genealogy-based rates from 2,500 to 50,000 years ago using mtDNA from populations in the Canary Islands, Polynesia, Micronesia, North America, Taiwan, Indonesia, and Oceania. The populations were selected based upon relative isolation and the  available archaeological dates for the time of first human arrival, haplotypic data from neighboring regions, and indigenous haplotypes for that region.

The authors were able to calculate that the evolutionary mutation rate between approximately 2,500 and 50,000 years ago was much different than that from 50,000 to 6 million years ago. They suggest that since earlier mutation rates, ones based upon pedigrees, are not affected by the processes of
bottlenecks and selection, except for purifying selection on lethal alleles, they can’t weed out the effects demographic processes. Using their time-dependent approach they observe that molecular clock was accelerated for large Neolithic populations and is similar to the pedigree rate, but for the smaller Paleolithic hunter-gatherers it was much lower…. makes sense, as populations grow, variability accelerates.

B. M. Henn, C. R. Gignoux, M. W. Feldman, J. L. Mountain (2008). Characterizing the Time-Dependency of Human Mitochondrial DNA Mutation Rate Estimates Molecular Biology and Evolution DOI: 10.1093/molbev/msn244

Joyce Marcus has published a bold review in the Annual Review of Anthropology where she argues that anthropology must be willing to generalize — cultures must be compared and contrasted in order identify similarities in the ways cultures have responded to challenges. In other words, relativism has no place in trying to understand the evolutionary pattern to human social structure.

She further argues that such a comprehensive and comparative analysis of cultural evolution must be done with collaboration between ethnologists and archaeologists. She stresses the impact of archaeology has in investigating cultural evolution, using the transition to agriculture and animal domestication as a critical moment when we can see the emergence of institutions not seen in previous lifestyles. She further relates the relationship between ethnology and archaeology is analogous to that,

“… between zoology and vertebrate paleontology. Zoologists are able to study both muscle tissue and behavior at a level of detail unavailable to paleontologists. Paleontologists, however, can find the muscle attachments on fossil bones that provide evidence for specific muscles; they can then draw on the zoological literature both on those muscles and on the behavior they reflect. Paleontologists can also elucidate long-term trends and recover the skeletons of transitional species unknown to zoology; such fossils show us the order in which certain structures (and hence behaviors) arose. In an important sense, the fossil record is the proving ground for any theory of change based on comparisons of living species.”

In order for us to understand how cultures evolve, she’s very right, cultural anthropologists and archaeologists do need to collaborate. Hell, archaeologists even need to understand that they’re not just digging up cultural noise. Both disciplines need to agree upon a common terminology and see that cultures can be compared. But I don’t know if many cultural anthropologists are ready to hang up their relativist coats on the hanger just yet.

Joyce Marcus (2008). The Archaeological Evidence for Social Evolution Annual Review of Anthropology, 37 (1), 251-266 DOI: 10.1146/annurev.anthro.37.081407.085246

A new paper in PNAS reports on an interesting find from a 12,000-year-old Natufian burial complex in the Hilazon Tachtit cave site in Israel — a shaman, which is unlike any other Natufian burial known to date. Before I get into the details of the paper, let me first introduce the Natufian culture and the ecological context members of this culture lived in.

Map of the Hilazon Tachtit Cave Site, Israel

The Natufian culture existed in the Levant from 14,500 to 11,500 years before the present. They were hunter gatherers at first and had a microlithic industry, perfecting short blades and bladelets. Two different human burials at the Ein Mallaha and Hayonim sites include dogs, suggesting they domesticated dogs around 12,000 years ago. The spread of the culture can be estimated by the presence of Anatolian obsidian and shellfish from the Nile-valley being found at Ein Mallaha.

Around 12,800 to 11,500 years ago a climate shift occurred. There are many names for this climate change, I’ll call it the Younger Dryas event. During this period, there was a rapid return to glacial conditions caused by a significant reduction of the North Atlantic thermohaline circulation. And by rapid I mean it happened within 10 years. The cold and dry Younger Dryas climate lowered the biological carrying capacity of the Levant. This ecological change from the Younger Dryas forced cultures into planting seeds obtained from elsewhere, and practicing agriculture.

Illustration of the Shaman Grave from Hilazon, Tachtit, Israel

Okay going back to the paper, archaeologists have recently excavated the Hilazon Tachtit cave site. Hilazon Tachtit is located about 15 km west of the Sea of Galilee in Israel. The site is dated to be 12,400 – 12,000 years old, right at this ecological and cultural transitional period. The site is primarily a burial ground of at least 28 Natufian individuals. Most of the remains are buried in one collective pit, but one burial was special. The remains of a 45 year old woman was separate and accompanied by lots of animal remains. She had bone spurs on her pelvis and spine, indicating she suffered physical ailments. Accompanying her burial are the remains of the tail bones from a cow, a wing bone from a golden eagle, a forearm of a boar, 50 tortoise carapace pieces, two marten skulls and a large foot from another person. She’s intricately buried in a certain position with a stones arranged in a certain fashion and unlike the other individuals.

Some Animal Remains From the Shaman Burial in Hilazon Tachtit, Israel

The authors argue that she was a shaman. Although the term shaman originally comes from the Tungisic speaking people from Siberia, many gatherer groups and small-scale agricultural cultures have had a shamanistic role — a member of the community who functioned as an intermediate between the human and spirit world. They were healer-magician hybrids. The elaborate burial of this physically disabled woman accompanied with tortoises, cow tails, eagle wings, and fur-bearing animals fall in line with our observation of other shaman burials found throughout the world.

The presence of a shaman in this critical transitional period of human cultural evolution suggest that the seeds of organized religion were already planted. Now, there are controversial depictions of shamans in cave art from 15,000 years ago, but this 12,000 year old burial is the first physical evidence of the ideological and socioeconomic changes that accompanied the forager-to-farmer Neolithic transformation. The development of spiritual ideas and religion are a big part of human cultural evolution. We don’t know exactly when human ancestors developed such thoughts, it could certainly be earlier than 12,000 years ago, but at least we now know that early Neolithic peoples, like the Natufians had at least one shaman.

When do you think religious thoughts emerged during human evolution. Oh yeah, I have to ask, does anyone roll shaman in WoW?

L. Grosman, N. D. Munro, A. Belfer-Cohen (2008). A 12,000-year-old shaman burial from the southern Levant (Israel) Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0806030105