For many people, the word archaeology conjures up visions of researchers digging up old things like ancient tools or pottery.
But what if archaeologists found a single strand of hair or even smaller “artifacts” from deep below the ground surface? Adelphi anthropologists Brian Wygal, PhD, associate professor and director of the Environmental Studies and Sciences program, and Kathryn Krasinski, PhD, assistant professor of anthropology, made just such a discovery. Their article “Archaeological Recovery of Late Pleistocene Hair and Environmental DNA From Interior Alaska,” was recently published in Environmental Archaeology: The Journal of Human Palaeoecology.
In the article, the research team describes their methods for the recovery and identification of the ancient hair specimen and environmental DNA (eDNA) from sediments dating back to the end of the last Ice Age, approximately 12,000 years ago. The discovery of hair is exceedingly rare in deposits this old, which makes this particular find very exciting.
Drs. Wygal and Krasinski made the discovery at the Holzman archaeological site along the west bank of Shaw Creek, about 70 miles southeast of Fairbanks, Alaska. The Holzman site is one of the earliest archaeological sites in the Americas. There, Adelphi researchers and their multidisciplinary team of students and experts from around the world, have been conducting wide-ranging analyses from eDNA to environmental analyses that have contributed to expanding our understanding of human responses to climate changes.
“Ancient hair and remnant plant DNA are important environmental proxies,” said Dr. Wygal. “Preserved for many thousands of years, they can help to improve our understanding of late Pleistocene environments and how humans lived and adapted over millennia.”
However, recovery of small artifacts such as hair from archaeological sites has been rare, and extraction of the fragile strand of hair from the surrounding mass was uniquely challenging. The approach for locating and recovering ancient hair and DNA described by Drs. Wygal and Krasinski and several co-authors serves as a useful case study for finding and studying the trace evidence left behind by past human activities. Their work attempts to put these activities into the context of their local environment.
To extract and learn from DNA preserved in the cold soils of Alaska, Drs. Wygal and Krasinski gathered soil from various depths of earth, representing progressively distant time periods, in medical-grade sterile vials. These samples were immediately frozen and shipped to the Paleogenomics Laboratory at the University of California Santa Cruz for examination.
Working with students in the Adelphi University archaeological laboratory, the team filtered the bags of soil through small wire mesh shifters. The sediment falls apart very easily, like a clump of salt or sugar, and the hair was recovered this way from sediments collected from an ancient campfire.
Such a discovery would be unlikely out in the field, but in the carefully controlled environment of the lab, the scientists can look for even the smallest of artifacts. Additional packages of sediment were sent to David McMahan, a private forensic anthropologist in Tennessee, for water flotation and more dry sieving where additional hairs have also been found. One of the hair specimens was then sent to Lakehead University in Toronto, Canada, where Jessica Metcalfe, PhD, assistant professor of anthropology, worked to identify the hair. There, its microscopic structure was compared to that of other known animals from that period including the wooly mammoth, American bison, Pleistocene horse, humans and others.
The hair was 8.8 centimeters long, brown and slightly wavy. By comparing macroscopic and microscopic features such as the structure of the root and the shaft, medulla, cuticle and surface, the researchers were able to rule out certain species as the source and narrow down the field of possibilities. It seems it was not an ancient human hair but rather one from either a mammoth or bison. Knowing that bison had become extinct about 1,000 years before the hair existed based on radiocarbon dating, the researchers sought greater clarity into its source.
To more accurately identify the hair, it was then sent to the Paleogenomics Laboratory of Beth Shapiro, PhD, an expert in molecular and genomic evolution and ancient DNA at University of California Santa Cruz (UCSC). The conclusion, based on the genomic profile, was also not completely clear. Ancient DNA (aDNA) often degrades and presents mostly as fragmentary segments so it can be difficult to piece together an exact match, and this analysis was also not completely definitive.
“Like many projects in science, we cannot always have 100 percent certainty,” Dr. Wygal said. “However, based on both the forensic and aDNA information, we can conclude the hair most likely originated from a bison.”
“Paleoenvironmental reconstructions of specimens from various strata on interior Alaska are essential to understanding the phases of transformation from the arid steppe ecosystem of the last Ice Age to the mesic boreal forest that arose during the middle Holocene,” Dr. Krasinski said. “Comparisons with existing data, such as analysis of other ancient hair samples and newer methods like eDNA recovery, can advance our understanding of ancient environmental changes at the hyper-local level of an individual archaeological site.”
Environmental DNA (eDNA)
Environmental DNA is genetic material that can be found in nature in the absence of a readily identifiable source, for example, DNA from a decomposed plant or body, bones, hair or fur, or feces. DNA can also be found free-floating in water from the same types of sources. All living things shed DNA regularly so it is all around us everywhere. Eventually it ends up in the soil where it can sometimes be preserved.
“In Alaska, eDNA work has been quite limited,” Dr. Wygal said. “At the Holzman site, we sampled six late Pleistocene and early Holocene sediments for study at the Paleogenomics Laboratory at UCSC.” These samples date from roughly 9,000 to 14,000 years ago.
The layers of earth examined by the team contained signs of ancient cooking, including burned wood carbon and bones dated back to 14,000 years old, the period when people first began to use the Shaw Creek area. The remains of birds and charred mammal bone fragments identified as bison and other animals have been found around cooking hearths dated to 13,600 years followed by a series of younger occupations buried in a well-stratified context. There were five stone tools and a lot of stone flaking debris made from chert, siltstone and quartz. Long bones from animals were also found, which were broken for marrow extraction. Together, these finds provide evidence of butchery and cooking in the area.
Radiocarbon dating revealed multiple hearths with overlapping ages at that location, suggesting repeated occupation of the site, perhaps seasonally. Over millennia, people periodically returned to the hill slope overlooking Shaw Creek.
“Detailed plant biodiversity analyses from incremental depths of the earth reveal what plants existed and how the flora evolved over time, in response to environmental changes,” said Dr. Krasinski.
The significance of this publication is the successful integration of cutting-edge environmental DNA methods with established archaeological methods to better understand the natural environment of a single archaeological site in rural Alaska. Through the collaboration of Adelphi faculty with students and professional colleagues around the world, we have a clearer picture of the lives of the first Americans and how they interacted with various animal species during a time of tremendous climate warming.
This project has been continued by student research assistant MacKenzie Pina, who is majoring in anthropology at Adelphi, for her honors thesis project. Pina has already discovered additional hair samples from ancient hearth deposits.
*Reference: Brian T. Wygal, Kathryn E. Krasinski, Jessica Z. Metcalfe, David McMahan, Charles E. Holmes, Barbara A. Crass, Teresa A. Wriston, Sabrina Shirazi, Alisa Vershinina and Beth Shapiro (2022): Archaeological Recovery of Late Pleistocene Hair and Environmental DNA From Interior Alaska, Environmental Archaeology, DOI: 10.1080/14614103.2022.2031836