For archaeologists, ancient bones and stone tools are important lines of evidence, but sometimes the answers to our past can be found in piles of human excrement, as a major new analysis shows.
From 2002 to 2010, aArchaeologists collected dozens of coprolites, or dried droppings, from Oregon’s Paisley Caves, the oldest dating back 14,000 years. A genetic analysis of the coprolites suggested that they came from humans, but some researchers questioned this result, citing possible contamination of the samples. Poop progeny remained unsolved for years, but new research is providing a fresh look at these stale but incredibly important manure piles.
Humans first entered in North America around the end of the last ice age, sometime between 20,000 and 15,000 years ago. More confirmation of exactly when and how this migration I take plaCe would be a big deal, even if the evidence in question is literally littered with junk.
The coprolites, to last so long, require an arid environment. There are many dry caves in western North America, but the Paisley Caves are special in that they are the only caves that harbor evidence of human activity dating back to the Pleistocene-Holocene transition.
G / O Media may receive a commission
That being said, this evidence is not great. Other than the alleged human coprolites, the only other evidence in the Paisley Caves of this period tends to be flakes from stone tool making (which cannot be reliably dated) and butcher marks on the bones of possible prey. . (which could actually be caries marks made by non-human animals). This is where ancient poop can help, when skeletal or other lines of evidence are scarce or nonexistent.
“The most compelling evidence for many archaeologists was a collection of preserved feces containing Native American mitochondrial DNA (mtDNA) deposited 14,400 to 14,000 years ago, making them the oldest directly dated human remains in the Western Hemisphere,” John Blong , co-author of the new study and an archaeologist from Newcastle University, wrote to Gizmodo in an email. However, this evidence was criticized because several of the coprolites contained human and dog mtDNA, suggesting that human mDNA may be the result of contamination of the overlying layers. Nobody doubts that the coprolites are as old as the radiocarbon dates say, they only doubt that they are human. “
That the previous mtDNA analysis was deficient is a clear possibility. People and animals have been sharing these caves for millennia, so it is very possible that the genetic material of a pile of poop leaks to others.
“If you’ve ever watched a crime show on television, you know that DNA can go everywhere,” Blong said. “Organisms constantly remove DNA from hair, skin cells, sweat, saliva, etc.”
At the same time, DNA is soluble in water, making it highly mobile in wet environments.
“Although the interior of the Paisley Caves is very dry, we see signs in the sediments that there were occasional short-term wetting events,” Blong explained. Imagine a storm with heavy rains blowing in the caves. The rain penetrates into the sediments of the cave and dries up a day or two later. Even in this short period of time, water can transport human DNA left behind by a later group to the deeper sediments representing an earlier time. ”
Fortunately, DNA is not the only clue available to scientists, as coprolites also contain fecal lipid biomarkers, which can bind to certain types of animals. In addition, lipids: organic molecular compounds that include fats, oils, steroidsand other biological firms: They are not very soluble in water, so they do not tend to move around the caves when things get wet. They are also chemically stable, so they hold well for long periods of time.
“These characteristics make lipids a more reliable source for identifying human coprolites in an environment where sediments in the cave occasionally get wet,” Blong said.
With this in mind, Blong, along with study co-author Lisa-Marie Shillito and other colleagues, analyzed the lipid biomarkers found in 21 coprolite samples taken from Paisley caves, all of which were previously found to be of human origin. through the analysis of mtDNA. The researchers conducted tests to determine the content of sterols and bile, to distinguish human feces from those produced by other animals. The researchers then compared these samples to the surrounding sediment, discovering that minimal leaching occurred between the coprolites and the cave environment.
Of the 21 samples analyzed, 13 were identified as belonging to humans, two of which had previously been dated within the 14,000 year time frame. Interestingly, one poop sample was linked to a panther and another to a lynx. Details of this analysis They were published today in Scientific Reports.
“Our study addresses persistent criticisms of DNA evidence for the earliest human occupation of the Paisley Caves,” said Blong. “We addressed the issues of possible DNA contamination through analysis of fecal lipid biomarkers, providing evidence that DNA was likely moving from younger human occupations to older cave sediments and coprolites, but also confirming that people were camping. in the caves already 14,200 years ago. “
Katelyn McDonough, Ph.D. A candidate in the Department of Anthropology at Texas A&M University, he told Gizmodo that the fecal biomarker approach is “very exciting,” since lipids “are better preserved and move less than other materials, such as DNA.” Overall, “this study advances and demonstrates the fecal biomarker approach and is a good argument for using this method in conjunction with DNA analysis in the future,” said McDonough, who was not involved in the new research, although she passed time working in the Paisley caves.
McDonough said she was “somewhat surprised” by the disagreement between DNA and biomarker readings for some of the coprolites, “but that shows that we should not always rely solely on DNA and that multiple lines of evidence are better, when possible.” . . “
For the new study, the authors also directly dated a cultural remnant found in the caves. A fragment of cattails, either from a basket or mat, was found to be approximately 14,000 years old, “further confirming the earliest human occupation,” Blong said. McDonough said the directly dated basketry piece is “incredible” and an “extremely unique insight into plant use and textile production some 14,000 years ago.”
“We still have a lot to learn about when the first people arrived in the Americas, where they came from and what routes they took to get here,” Blong said. “Our study adds to the growing evidence that people were in the Americas more than 14,000 years ago, before the widespread Clovis culture.”
In fact, the new document is further proof that humans reached this part of the world.d before the rise of the Clovis culture and its iconic stone tool technology. The Clovis people, who emerged about 11,500 to 11,000 years ago, were once considered the first inhabitants of North America, but this theory is increasingly in doubt.
As Blong pointed out, these coprolites are the oldest human remains directly dated to the Western Hemisphere, but there is other important archaeological evidence to consider.
A study Since last year, for example, it showed some of the first human testing in North America, specifically at the Cooper’s Ferry site in western Idaho. Stone tools, animal bones, traces of bonfires, and other signs of human occupation date back to 16,560 and 15,280 years ago.
It’s also worth noting that the colossal ice sheet that separates North America from Siberia began to melt about 14,800 years ago. That the humans were living in the Oregon Paisley Caves shortly thereafter isn’t a big surprise, but it’s nice to have this additional poop evidence.
Excitingly, these human coprolites have more stories to tell. As Blong told Gizmodo, he and his colleagues are currently analyzing the coprolites to find out what these pioneer humans were eating.
“Stay tuned for a more exciting investigation of the Paisley Caves,” he said.
.
