In February 2012, the Institute of Applied Ecology of the North (part of North-East Federal University, or NEFU) and the Sakha Academy of Sciences (ANRS) announced discovery of three remarkable fossil specimens with preserved soft tissues, from the northern part of the Sakha Republic (Yakutia). These specimens– apartial carcass of ayoung woolly mammoth, the head and partial body of ahorse, and acomplete carcass of ayoung male steppe bison– were found by associates of Mr. Vasily Gorokhov, leader of the Yukagir community, of the Ust-Yanskiy District, northern Yakutia. Ateam of Yakutian, Russian, and foreign scientists studied all three specimens, with results to be published elsewhere. In addition to learning about these specimens, we discussed with Mr. Gorokhov two sites with notable concentrations of fossil remains: Sappliva (also called Muus Khaya), near the Yana River archaeological site excavated by Vladimir Pitulko and colleagues, and apreviously unreported site in northern Yakutia, Bulchurkhan Yuriuetta. With help from our Yakutian colleagues, we arranged ajoint field expedition with Mr. Gorokhov for late summer 2012.Although our interests and his were quite different, we developed aproductive partnership, the details of which Iwill outline today.
Mr. Gorokhov was interested mainly in collecting mammoth tusks for the commercial ivory trade. In contrast, our research usually involves detailed laboratory analysis of tusks to extract data on the growth histories and ecologies of mammoths. Clearly, both goals could not be fully satisfied with the same specimens, at the same time. Fortunately, some data on mammoth tusks can be acquired from simple measurements and photographs, and for this type of study, we were able to benefit even from specimens that were destined to be sold. In addition, we were able to shift our primary focus from mammoth tusks to mammoth molars. Molars grow in much the same way as tusks and yield similar kinds of data on life history. Atusk is better for us, because it yields arecord of multiple decades of life and is relatively easy to sample, but molars often record data on an interval of 5-10 years, and for some purposes, this is enough to be useful. Our agreement with Mr. Gorokhov was essentially that he would take the tusks (allowing us to measure and photograph the best ones) and we would take the molars, which had little commercial value.
For tusks that we measured and photographed, we used photogrammetric software, back in our lab in the US, to generate accurate 3-dimensional models from aseries of photos taken from points all around the specimen and at different levels. We will next subject these models to quantitative study to determine the growth parameters responsible for the form of each tusk. By comparing multiple specimens, we can learn how growth and form differ in males and females, how they vary among individuals of the same sex, and how they change with age.
A second goal of our research was to visit the discovery site for each of the remarkably preserved carcasses we had studied in Yakutsk, to gain some first-hand understanding of the lithology, the stratigraphy, and the nature of the fossil assemblage associated with each. The mammoth and the horse had been found relatively close to one another at alocality known as Oyagoskiy Yar, on the north-facing coast of the Laptev Sea. This region was moderately fossiliferous, and yet there was no evidence of any unusual concentration of remains that would suggest aunique setting for fossil preservation. The same characterization held for the locality that had produced the steppe bison, along the shore of Lake Chukhchalach.
Although we have not yet had the opportunity to undertake detailed laboratory analysis of the mammoth, the horse, or the bison, we anticipate being able to do this in the future, and we should be able to determine, among other things, the season of the year at which each died and their condition in the years prior to death. This kind of analysis could shed light on their causes of death and help to reconstruct aspects of the environment in which they lived. However, our ability to interpret such data would be greatest if we could analyze alarger sample of isolated deaths from broadly similar preservational settings. Therefore, athird goal of our fieldwork was to collect molars of mammoths in particular, and other fauna, if possible, to document general patterns of seasonal mortality in this fauna. We expect cause of death and season of death to vary among individuals, but the distribution of season of death in alarge sample should reveal how seasonal changes in weather conditions, food availability, and risk of accidental trauma affected mortality in Pleistocene populations. Season of death can be determined by histological and microCT analysis of the growing ends of tooth roots, supplemented by serial analyses of oxygen, carbon, and nitrogen isotope ratios in dentin hydroxyapatite and collagen. It depends on finding teeth that were still actively growing at the time of death, yielding dentin formed over several years prior to death. Fortunately, this is easy to evaluate by inspection of tooth roots at the time of collection. In this fashion, by prospecting many kilometers of coastal cliffs, inland outcrops, river margins, and margins of thermokarst lakes, we found 38 molars (mostly mammoth) with open roots suitable for analysis. These specimens constitute an excellent comparative sample.
The fourth goal of our fieldwork was to sample sites with unusual concentrations of fossil remains. At the new Bulchurkhan Yuriuetta locality, we collected 79 molars (mostly mammoth) with open roots suitable for analysis. We also recovered lithic flakes at this site; together with clear signs of carcass processing on skeletal material, this represents strong evidence of human association at this site. It is not clear yet whether human activity is responsible for the deaths of all these animals, but human agency is at least involved in postmortem treatment of carcasses. To understand the formation of this site, we propose to determine the perimortem nutritional condition and season of death of many, if not all, of the teeth we collected. In addition, we will compare the patterns revealed in this sample with those from our sample of isolated deaths. These kinds of studies are extremely labor-intensive, but they have great potential to enhance understanding of human-megafaunal interaction during the Pleistocene history of this region.
We also pursued our fourth goal at Sappliva, the better-known locality with an unusual concentration of megafaunal remains adjacent to the Yana River archaeological site. Unlike Bulchurkhan Yuriuetta, this site has already been dated and is known to reflect atime 27,000– 30,000 years ago; it is one of the earliest well-documented human occupations of the high arctic. Unfortunately, late summer rains caused adramatic rise in the level of the Yana River just before we returned to conduct our main survey of this site. Because much of the site was flooded, we were only able to collect 15 teeth (again, mostly mammoth). Although this is asmaller sample than we would like to have collected, it should still allow us to gain new insights into alocality that is already important for our understanding of Pleistocene paleoecology and human activity. Agreat deal remains to be learned about these times and places, but studies such as those we have begun will elucidate the lives of both ancient humans and megafauna in unprecedented detail.
We are thankful to Vasily Gorokhov and his family, friends, and associates for helping us succeed in our objectives. Mr. Gorokhov’s unexpected death this past fall was aloss to us all. We are also grateful to our Yakutian colleagues for assistance before, during, and after our fieldwork.