Anthropology.net

By Jay Fancher

Oil transformed Dubai in the 1970s. The city now boasts the world's tallest building, giant malls, and some two million residents, who depend on desalinated seawater and air-conditioning—and thus on cheap energy—to live in the Arabian desert. (Credit: Jens Neumann/Edgar Rodtmann/NATIONAL GEOGRAPHIC)

To paraphrase Carl Sagan, science has a way of deflating human conceits.  Anthropology reveals that humans are special – just not for many of the reasons proposed throughout our history.  Thanks to biology, astronomy, and geology, we now know that:

• Modern humans are one species among many, not the pinnacle of all creation.

• We’re not the center of the universe; our planet orbits a fairly average star.

• We haven’t been around since the beginning of time – far from it.

On a 4.5-billion-year-old planet, with a 3.5-billion-year history of life, anatomically-modern Homo sapiens only go back about 200,000 years.  We’re brand new, a tiny blip on the geologic time scale!  Despite this, a new National Geographic article explores the possibility that the “Anthropocene” may have already begun.  Here is a brief excerpt:

Enter the Anthropocene—Age of Man It’s a new name for a new geologic epoch—one defined by our own massive impact on the planet. That mark will endure in the geologic record long after our cities have crumbled…Probably the most obvious way humans are altering the planet is by building cities, which are essentially vast stretches of man-made materials—steel, glass, concrete, and brick. But it turns out most cities are not good candidates for long-term preservation, for the simple reason that they’re built on land, and on land the forces of erosion tend to win out over those of sedimentation.

The author of the article, Elizabeth Kolbert, graciously agreed to an interview with Anthropology.net.  The text of our discussion, conducted via e-mail, follows:

Fancher: The greatest strength of anthropology is its all-encompassing view of humanity.  We’re proud of this breadth, frequently describing our work as the study of all people, in all times, and all places.  But, as you state in your article, stratigraphers take an extremely long view – the entire 4.5-billion-year history of Earth.  How can students of the human past benefit from this geological perspective?

Kolbert: I’m not sure I have a good answer for this.  As all anthropologists know, we are a young species.  So human history doesn’t tell us much about earth history.  What is particularly alarming about a lot of recent discoveries in geology is that you have to go way, way back – i.e., tens of millions of years – to find analogues for some of the things we are doing today, like, for example, acidifying the oceans.

Fancher: I was surprised to read that our proudest technological achievements might not be easy to recognize in the geological record.  It’s humbling to think that urban centers will ultimately be as fleeting in the geological record as short-term hunter-gatherer camp sites are in the archaeological record.  Despite our human desire to leave huge, everlasting monuments, is it better not to be noticed in the geological record?

Kolbert: Well, it’s not clear that we will be noticed, because it’s not clear there’s going to be anything around to notice us.  But we will be noticeable.  And certainly from the standpoint of the other organisms on earth, it would be a lot better if our impact were not so obvious.

Fancher: Some issues of scientific classification appear to have little practical relevance.  For example, the debate over whether Pluto qualifies as a planet or not.  In your article, Dutch chemist Paul Crutzen concludes that the value of the Anthropocene classification goes far beyond textbook revisions.  Can you elaborate on the meaning of the Anthropocene?

Kolbert: Officially, we live in the Holocene, or “wholly recent” epoch.  The Anthropocene translates basically as the man-made epoch.  It’s an acknowledgment that humans, rather than what are sometimes quaintly called “the great forces of nature,” have become the driving force on the planet.

Fancher: How might recognition of a geological epoch called the Anthropocene influence human behavior?

Kolbert: I end the piece with a quote from Paul Crutzen, the Nobelist who coined the term.  Crutzen says, “What I hope is that the term ‘Anthropocene’ will be a warning to the world.”  I think what he means by that is: we are now in the driver’s seat.  Unfortunately, we don’t really know how to operate the vehicle.  So we’d better think about what we’re doing very carefully.

Many thanks to Elizabeth Kolbert for writing such a thought-provoking article, and for agreeing to this interview.  Enter the Anthropocene – Age of Man is part of National Geographic magazine’s year-long coverage of the global human population reaching 7 billion.

What do you think about the possibility of a geological epoch called the Anthropocene?

In late May, Paul Sereno was in town to talk at the 2008 conference titled, ‘Integrating Evolution, Development, & Genomics.’ He was invited to also give a talk titled, “Living Lakeside in the Sahara: A Chronicle of Holocene Adaptation,” to the Primate Biology Group. I eagerly attended. Paul Sereno, if you don’t know, is primarily a dinosaur paleontologist and geologist. And a really well known one at that. He’s discovered around 10 or so new dinosaur species.

But, in 2000 while on a excavation for dinosaurs and giant crocodiles in Niger, National Geographic photographer, Mike Hettwer, stumbled upon a Neolithic graveyard. Sereno shifted his search for dinos to studying these bodies and the artifacts associated with them. He discussed his finds in his talk.

It was so inspiring to be there, and I’m not alone in sharing this sentiment. I was attending the talk with a couple of friends, and they also felt the same way. The clarity and enthusiasm with which Sereno explained the site and his work was impressive — I’ve rarely seen someone so excited to explain so much material. Sereno’s definitely got a reason to be enthusiastic — he has what is now most likely the largest collection of Early to Mid-Holocene bones ever discovered at a single site in Africa.

Gobero, a Neolithic Site in Niger.

After the talk, I got a chance to have a one and one with Sereno. He let me know about his time frame and publication plans. I’m happy to see that everything has come to fruition. Published today, in the open access journal PLoS One is Sereno et al.’s analysis of the site, “Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change.”

In the paper, Sereno and team describe the paleoecology of the site and climatic change. They include their interpretation of the burials and associated artifacts. I’ll do my best summarizing the piece in this blog post, but I really recommend you read this gem for yourself. It is open access and well written — you don’t have really any excuse not too.

This site has been called Gobero, after the local Tuareg name for the area. About 10,000 years ago (7700–6200 B.C.E.), Gobero was a much less arid environment than it is now. In fact, it was actually a rather humid lake side hometown of sorts for a group of hunter-fisher-gatherers who not only lived their but also buried their dead there. How do we know they were fishing? Well, remains of large nile perch and harpoons were found dating to this time period.

Of the 67 burials excavated, five of them date to an occupation span from 9,750 to 9,500 years ago. That’s 250 years or so. Looking at photos of the field site, it is hard to believe these prehistoric people got comfortable in Gobero. They began making pottery and ritually burying their dead. One of these guys, G3B8, is a 2 meter tall dude (that’s like 6 feet 6 inches!). He’s pictured below, buried rather utilitarian, with hands covering his mouth and crossed feet, just as he was found:

G3B8, a 6 foot 6 individual from Gobero, Nigeria. Photo (c) Mike Hettwer, courtesy Project Exploration.

G3B8 is not alone in his stature and robustness. There other burials, both male and female, from this time frame are of similar height. These Early Holocene hunter-gathering fishermen also have characteristic skulls — long and low, with a unique occipital bun and broad nasals. These features aren’t restricted to only adults, in fact, juveniles as young as 4 years exhibit similar traits which are not shared by the later inhabitants of Gobero. These bodies were tightly bound when buried.

Around 6200 B.C.E (8,200 years ago) Gobero began to resemble what we see today. The paleolake dried up, and these tall, robust inhabitants hauled out. The youngest early-Holoecene burial dated to 6210 B.C.E. This regional climate change persisted for about 1,000 years, correlating to climatic deterioration across the Chad Basin and linked to the chilling of the North Atlantic.

The return of humid conditions came about immediately after this arid interruption. The lake refilled, and plants, animals and people moved back to Gobero. These favorable conditions persisted for much longer than the early Holocene occupation, roughly 2,700 years. The new settlers were anatomically much different from their predecessors. For starters, they are shorter. They’ve got tall, narrow skulls, with long faces. This guy, dubbed G1B11, is a mid-Holocene adult male dating to around 4,645 B.C.E. is a good example of the different morphology:

G1B11, an adult male from Gobero, Niger. Photo (c) Mike Hettwer, courtesy Project Exploration.

To better illustrate the differences between the robust, early occupants and the latter, gracile ones. Check out this comparison. On the left is a 9,500 years old skull of this mature male. The eye sockets are square, the cranium is low and check out those nasals! On the right is a 5,800 years old skull of a young adult. While not as mature as his 3,700 counter part, you can see the anatomical differences for yourself — a much taller cranium, look at the forehead.

Kiffian (9,500 year old) Skull vs Tenereian (5,800 year old) Skull from Gobero, Niger. Photo (c) Mike Hettwer, courtesy Project Exploration.

Tenerean Bracelet Girl. Photo (c) Mike Hettwer, courtesy Project Exploration.

7 of 35 burials excavated from the mid-Holocene occupation were buried with artifacts. I remember Sereno showing us a photograph of an individual buried with a turtle shell underneath him. I didn’t catch the specimen number at the time, and now found out that guy is G1B11 — pictured above. You can see in the middle image the carapace functioning as an eternal bed. The mid-Holocene occupants were much more symbolic than the early Holocene individuals. They buried their dead with more elaborate artifacts, such as this 11 year old girl (G1B2) who is wearing an upper-arm bracelet carved from the tusk of a hippo. She’s believed to have died around 4,835 years ago.

Why were these people burying their dead with beads, bracelets, and on turtle shells? Sereno et al. suggest that the latter occupants were more pastoralists and agriculturalists — because archaeological evidence for grain and remains of domesticated cattle are present in the midden from this time period. Their gracile frames support this lifestyle, as well. Additionally, curious looking fine-grained green rocks were used to make points, scrapers and adzes from this time period. This rock isn’t found in Gobero. Actually, this feldspar rock came from Alallaka — a prehistoric rock quarry about 160km north of Gobero. The relaxation from gathering and hunting for food allowed for people to develop new skills, such as jewelry making and symbolic burials — even trade their skills for green rocks from the north.

So who were these people?

Sereno et al. did a principal components analysis of craniofacial dimensions of the skulls from both periods and compared them to Late Pleistocene to mid-Holocene populations from the Maghreb and southern Sahara. The early Holocene occupants are similar to remains from Maghreb Capsian, Maghreb Iberomaurusian, Mali, Mauritania. The mid-Holocene occupants are unlike any other population tested. That doesn’t tell us much about who they were.

Kiffian Wavy Pottery. Photo (c) Mike Hettwer, courtesy Project Exploration.

So Elena Garcea, a specialist in African archaeology from this period, analyzed the material culture. She believes that the bone harpoon points and hooks, as well was the dotted wavy-line, zigzag ceramic exhibit attributes of the Kiffian people. Kevin MacDonald described the Kiffian technology, one that specialized in harpoons and microliths, in the text “Archaeology and Language.” Several other publication also support this claim. On Sereno’s website, there are more photos of the bone harpoons and pottery. I don’t have any examples of Kiffian artifacts to compare, so I’ll just trust that Garcea and Sereno got this identification.

The mid-Holocene occupants are believed to be Tenereans. Their affinity for green feldspar and the small projectile points as well as the disc knives characterize the Tenerean material culture. An example of Tenerean style projectile points from Gobero is below: IMAGE REMOVED AS PER MIKE HETTWER’S REQUEST.

Tenerean Triple Burial, from Gobero, Niger. Photo (c) Mike Hettwer, courtesy Project Exploration.

If you’re not completely floored by the wealth of archaeological and anatomical material from Gobero, let me share with you the Tenerean triple burial. The triple burial includes a female, presumably the mother, laid to rest on her right side who died somewhere around 5,300 years ago. Facing her are two children (ages 8 & 5 years old) and buried on their left side, interpreted as her children. These people were buried with their arms and legs around each other and holding hands. Abundance of pollen residues underneath them suggest they were buried on a bed of flowers. Multiple burials like this, and in this condition are rare. Furthermore, this is first triple burial ever discovered on Africa.

Sereno did not excavate these individuals like a normal archaeologist would. Instead, being a dinosaur specialist, he jacketed the remains.

Gasp!

You’re probably thinking, “Sacrilegious technique! He shoulda used brushes and dental picks, removing each bone and shipping them off for study in the lab.” But had he not done so, burials like the triple burial would have not survived excavation — the extreme heat of the Sahara has made the bones exceptionally fragile. That’s why having a multidisciplinary approach to doing this sorta fieldwork works. And I commend Sereno for taking these measures to preserve the bodies and site.

This publication has shown us very eloquently how important Gobero is to our understanding of climate change and prehistoric peoples and archaeology of the Sahara. As more and more of Gobero becomes exposed and weathered, more and more of it will be lost to time if we do not support Sereno’s research. Hettwer has documented the impact 5 years has made on one such exposed skeleton:

Weathering of an exposed skeleton at Gobero, Niger. Photo (c) Mike Hettwer, courtesy Project Exploration.

I’ve mentioned before only 67 burials were excavated. There are at least 182. Gobero needs to be preserved, for its wealth of evidence and the cultural heritage it provides Niger.

Sereno, P.C., Garcea, E.A., Jousse, H., Stojanowski, C.M., Saliège, J., Maga, A., Ide, O.A., Knudson, K.J., Mercuri, A.M., Stafford, T.W., Kaye, T.G., Giraudi, C., N’siala, I.M., Cocca, E., Moots, H.M., Dutheil, D.B., Stivers, J.P., Harpending, H. (2008). Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change. PLoS ONE, 3(8), e2995. DOI: 10.1371/journal.pone.0002995

The following post doesn’t directly have much to do with anthropology. Indirectly, it sure does, especially to those out there that study human population expansions and the Pleistocene-Holocene transition or even anthropologists interested in prehistoric paleoenvironments and the context of how people were living and what they were doing during that time.

Anyways, this post is about a PLoS Biology paper. PLoS Biology is an open access journal that has just published a paper which investigates woolly mammoth extinction. The authors of the paper, “Climate Change, Humans, and the Extinction of the Woolly Mammoth,” ultimately conclude that both climate change and human hunting were critical factors in woolly mammoth extinction. Not a really Earth shattering conclusion, I know… but there has been some discussion whether or not climate change or human hunting was more impactful.

Right before the Holocene, the global climate was warming up. And most woolly mammoths died out during this time, the end of the Pleistocene (12,000 years ago). That’s what got many people to consider that warm temperatures may have driven the extinction of this cold-adapted species. But, the species had survived previous warming periods, and in places like St. Paul Island, Alaska and Wrangel Island they lasted up until 3,700 years ago. This is what got other people to think that the extinction of the woolly mammoth was due to the effects of human population expansion.

From the author’s summary,

“In this study, we combined paleo-climate simulations, climate envelope models (which describe the climate associated with the known distribution of a species—its envelope—and estimate that envelope’s position under different climate change scenarios), and a population model that includes an explicit treatment of woolly mammoth–human interactions to measure the extent to which climate changes, increased human pressures, or a combination of both factors might have been responsible. Results show a dramatic decline in suitable climate conditions for the mammoth between the Late Pleistocene and the Holocene, with hospitable areas in the mid-Holocene being restricted mainly to Arctic Siberia, where the latest records of woolly mammoths in continental Asia have been found. The population model results also support the view that the collapse of the climatically suitable area caused a significant drop in mammoth population size, making the animals more vulnerable to increasing hunting pressure from expanding human populations. The coincidence of the collapse of climatically suitable areas and the increase in anthropogenic impacts in the Holocene are most likely to have been the “coup de grâce,” which set the place and time for the extinction of the woolly mammoth.”

I’m really not clear about how the authors established their population models. I’ll do my best to review them, though. The authors compared and contrasted the population sizes to the climatic conditions. Curiously, their results differ as they increase the n, but they were able to calculate,

“that the most suitable geographic area available to woolly mammoths increased by 7.7 million km² from the last interglacial, 126 ky BP, to 42 ky BP (from 0.3 to 8.1 million km²). There was a 0.5 million km² decrease in the most suitable area between 42 ky BP and 30 ky BP periods, and then a 3.7 million km² decrease between 30 ky BP and 21 ky BP (from 7.5 to 3.8 million km²). Finally, between 21 ky BP and 6 ky BP, there was a 2.9 million km² decrease. By the 6 ky BP period, only 0.8 million km² of the most suitable climatic conditions remained.”

This shows that with time, the available suitable habitats for the species reduced and did thus contributed to a reduction in woolly mammoth population sizes. Now the authors didn’t directly test the zooarchaeological record to directly correlate if human hunting or the side effects of human population expansion affected mammoth populations. But they did infer that their results of the incremental decrease in population sizes over time showed a “synergy” to the northward increase in human population densities during the Holocene.

So what about the mammoth groups in Alaska and the Arctic Ocean that persisted late after all the others died off? Their results actually show that these areas were largely unchanged by both climate and human impact. In fact, that climate change and human impacts were focused on mammoths in the northernmost land masses of Arctic Siberia and some arctic islands, “leaving them with nowhere to run away from extinction.”

Nogués-Bravo, D., Rodríguez, J., Hortal, J., Batra, P., Araújo, M.B. (2008). Climate Change, Humans, and the Extinction of the Woolly Mammoth. PLoS Biology, 6(4), e79. DOI: 10.1371/journal.pbio.0060079