Ancient bones and stone tools are important lines of evidence for archaeologists, but sometimes the answers to our past can be found in piles of human poop, as an important new analysis shows.
From 2002 to 2010 aArchaeologists collected dozens of coprolites or dried up droppings in Oregon’s paisley caves, the oldest of which were dated 14,000 years ago. A genetic analysis of the coprolites revealed that they are human. However, some researchers questioned this result and referred to possible contamination of the samples. The poop’s offspring remained unsolved for years, but new research provides a new look at this stale but incredibly important dung heap.
People came in first towards the end of the last ice age to North America, sometime between 20,000 and 15,000 years ago. Further confirmation exactly when and how this migration took place would be a big deal even if the evidence in question is literally crap.
Coprolites need a dry environment to last that long. There are many dry caves in western North America, but the Paisley Caves are special in that they are the only evidence of human activity from the Pleistocene-Holocene.
That said, this evidence is not great. Aside from the alleged human coprolites, the only other evidence in the Paisley caves from this period is flakes that are left on the bones of possible prey animals during the manufacture of stone tools (which cannot be reliably dated) and butcher marks (this could actually gnaw made by non-human animals). Ancient feces can help here – if skeletal or other lines of evidence are either scarce or nonexistent.
“The most compelling evidence for many archaeologists was a collection of native American mitochondrial DNA (mtDNA) faeces that were deposited between 14,400 and 14,000 years ago, making them the oldest human human remains in the western hemisphere,” said John Blong, co-author The new study and an archaeologist at Newcastle University wrote an email to Gizmodo. “However, this evidence was criticized because some of the coprolites contained both human and canine mtDNA, suggesting that the human mtDNA could be the result of contamination from 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 poor is a clear possibility. Humans and animals have shared these caves for MillenniaSo it is very likely that genetic material has been drained from one pile of feces to another.
“If you’ve ever seen a crime series on TV, you know that DNA can go anywhere,” said Blong. “Organisms are constantly losing DNA in hair, skin cells, sweat, saliva and so on.”
At the same time, DNA is water-soluble and therefore very mobile in damp environments.
“Although the interior of the paisley caves is very dry, we see evidence in the sediments that occasional wetting events have occurred,” said Blong. “Imagine a storm with heavy rain blowing into the caves. The rain penetrates the cave sediments and dries a day or two later. Even in this short period of time, the water can carry human DNA left behind by a later group into the deeper sediments that represent an earlier period. ”
Fortunately, DNA is not the only clue available to scientists, since coprolites also contain fecal lipid biomarkers that can be bound to certain animal species. In addition, lipids – organic molecular compounds to which fats, oils, Steroidsand other bio-signatures are not very soluble in water, so they don’t move in caves when things get wet. They are also chemically stable so that they can be kept for a long time.
“These properties make lipids a more reliable source for identifying human coprolites in an environment where cave sediments occasionally get wet,” said Blong.
With this in mind, Blong, along with co-author of the study, Lisa-Marie Shillito, and other colleagues, analyzed the lipid biomarkers found in 21 coprolite samples from paisley caves, all of which were previously detected by mtDNA analysis that they are of human origin. The researchers performed tests to determine sterol and bile levels to distinguish human feces from other animals. The researchers then compared these samples to the surrounding sediment and found that there was minimal leaching between the coprolites and the cave environment.
Of the 21 samples analyzed, 13 were identified as human, two of which had previously been dated to the 14,000 year period. Interestingly, one sample of faeces was connected to a panther and another to a lynx. Details about that analysis were published in Scientific Reports today.
“Our study looks at ongoing criticism of the DNA evidence of the earliest human occupation of the Paisley Caves,” said Blong. “We address problems of possible DNA contamination through analysis of fecal lipid biomarkers and provide evidence that DNA is likely to have moved from younger human occupations to older cave sediments and coprolites, but also confirm that humans were in 14,200 years ago camped in the caves. ”
Katelyn McDonough, Ph.D. The candidate at Texas A & M University’s Department of Anthropology told Gizmodo that the fecal biomarker approach was “very exciting” because lipids “preserve better and move less than other materials like DNA”. Overall, “this study advances and demonstrates the fecal biomarker approach and is a good argument for the future use of this method in conjunction with DNA analysis,” said McDonough, who was not involved in the new research, although she did has spent time working in Paisley Caves.
McDonough said she was “a little surprised” at the disagreement between DNA and biomarker readings for some of the coprolites, “but that shows that we shouldn’t always rely on DNA and that multiple lines of evidence are best when they do is possible.” . ”
For the new study, the authors also directly dated a cultural remnant found in the caves. A rush fragment, either from a basket or a mat, was found to be approximately 14,000 years old, “which further confirms the earliest human occupation,” said Blong. McDonough said the directly dated piece of wicker was “incredible” and “an extremely unique insight into plant use and textile production about 14,000 years ago.”
“We still have a lot to learn about when the first people arrived on the American continent, where they came from and how they came here,” said Blong. “Our study adds to the growing evidence that people were on the American continent more than 14,000 years ago before the widespread Clovis culture.”
Indeed, the new paper is further evidence that people have reached this part of the worldd before the advent of the Clovis culture and its legendary stone tool technology. The Clovis, which were created about 11,500 to 11,000 years ago, were once the first inhabitants of North America, but this theory is increasingly being questioned.
As Blong emphasized, these coprolites are the oldest directly dated human remains in the western hemisphere, but there is other important archaeological evidence that needs to be considered.
A study For example, some of the earliest evidence of people in North America was shown last year, particularly at the Cooper’s Ferry site in western Idaho. Stone tools, animal bones, traces of fireplaces and other signs of human occupation were dated 16,560 to 15,280 years ago.
It is also worth noting that the colossal ice sheet that separates North America from Siberia began to melt about 14,800 years ago. It’s no big surprise that people lived in Oregon’s paisley caves soon after, but it’s good to have this additional evidence.
Excitingly, these human coprolites have more stories to tell. As Blong Gizmodo said, he and his colleagues are currently analyzing the coprolites to find out what these pioneering people ate.
“Stay tuned for more exciting research from the Paisley Caves,” he said.