The first humans to arrive in North America lived rather hardscrabble — and unhygienic — lives. Archaeologist Dennis Jenkins from the University of Oregon discovered this firsthand while exploring eight small rock caves near the city of Paisley, Oregon. There he found copious amounts of fossilized feces, called coprolites, that had been left behind by the caves’ inhabitants. They were scattered all over the place, where children and babies would have played on the ground, and even by the fire, where food was cooked. “You can imagine what it smelled like … with … smoldering smoke, urine and feces … blood and bits of meat,” Jenkins says.
The poor standards of hygiene are hardly surprising to modern-day scientists, but the people who lived in the caves could never have imagined that their preserved waste would be the subject of scrutiny and debate by the archaeological community 14,000 years later.
Together with a series of other finds, the discovery of the human coprolites could deal a deathblow to the longstanding theory that the Clovis people were the first to arrive in North America, 13,000 to 13,500 years ago.
The fossilized feces, which have been dated to around the same time or just before the Clovis artifacts, indicate that human settlement in the Americas may have been carried out by multiple groups of people.
Clovis First takes root
For more than 50 years, many archaeologists have insisted that the Clovis culture was the first to be established in North America. This theory holds that the people from Asia began to migrate eastward at the end of the last glacial period. At that time, the sea level was more than 300 feet lower than it is today, and large areas of North America were covered by ice caps that were several miles thick.
As the climate warmed, the ice began to melt, and the glaciers retreated, opening an ice-free corridor that stretched south into what is now Canada from the Bering Strait, where the Beringia land bridge linked Siberia to North America. Herds of mammoths and other game animals followed the corridor, pursued by human hunters who arrived in the New World to find a veritable cornucopia of large herbivores such as bison and giant sloths, which were unused to people and their efficient hunting methods, making them easy and abundant prey.
Archaeologists named these people Clovis, after the city in New Mexico where the primitive culture’s distinctive stone tools were found in the 1920s. Subsequent Clovis finds reinforced this theory of the peopling of North America and also indicated that the new arrivals made their way across the continent over the next 500 years.
In the 1970s, several scientists began to challenge the Clovis First theory, including Tom Dillehay, who is now an anthropology professor at Vanderbilt University in Nashville, Tennessee. In 1977 he began excavating the Monte Verde site in southern Chile, which was dated to 14,600 years ago, more than 1,000 years older than the oldest Clovis find. But his contemporaries were skeptical — the dates of several other finds made around the same time had not held up to scientific scrutiny, reinforcing the Clovis Firsters’ belief that theirs was the correct theory. It took 20 years before the dates were finally accepted as valid.
Coprolites cast seeds of doubt
Then, in the early 2000s, Dennis Jenkins started digging up the floor of the Paisley caves and changed everything. The coprolites he found 6 feet underground, scattered among stone chippings and animal bones, attracted the attention of a scientist from England’s University of Oxford, who inquired about extracting genetic material from the feces. This had never been done before, and although Jenkins thought the man crazy, he agreed to cooperate.
The scientist was Eske Willerslev, a Danish evolutionary biologist who had been fascinated by North America’s native peoples since he was a boy. Willerslev is known both for his raucous vocabulary and his outstanding scientific work; he is widely acknowledged as a pioneer of fossil DNA. He has extracted mammoth DNA from the Siberian permafrost and sequenced a portion of the genome of the 4,500-year-old remains of a man who lived in Greenland.
In 2008, Willerslev, Jenkins and their team published their results. They had found human DNA dating to 14,300 years ago, evidence that people may have lived in North America long before Clovis was settled. The discovery altered the debate about when and how people came to North America and was, unsurprisingly, very unpopular among proponents of the Clovis First theory.
The old guard dismissed the study with an alternative explanation: The feces, they maintained, came from modern dogs, while the human DNA was from people who used the caves as a toilet at some later point. The DNA then seeped into the ground, where it was absorbed by the coprolites.
“Hell broke loose,” Willerslev says, “and we spent most of 2009 reacting to criticism from very agitated scientists.”
But Willerslev and Jenkins weren’t alone. As it turns out, plenty of scientists had alternative theories of their own about the earliest migrations to the Americas. Absent the threat of having their careers ruined by challenging the Clovis First orthodoxy, a new generation of archaeologists entered the field with fresh ideas and new research methods.
Counter-Clovis evidence mounts
With the floodgates opened, new excavations were organized, old ones were revisited, and the latest biotechnological advances, such as protein profiles and fossil DNA, were introduced.
In 2011, some of this new evidence came from Michael Waters of Texas A&M University, who published the discovery of more than 15,500 stone tools found at Buttermilk Creek, Texas. The tools were dated between 13,200 and 15,500 years old and, like Jenkins’ find, were inconsistent with the Clovis First paradigm.
Later that year, Waters and Willerslev published another discovery. They reexamined a mastodon unearthed in the state of Washington in the late 1970s, analyzing its DNA and using a standard method to date the spear that killed it. Their results showed that the spear struck the mastodon some 13,800 years ago — at least 300 years before Clovis.
There are other compelling studies. Geneticist David Reich of Harvard Medical School led the most extensive comparison to date of DNA markers from modern indigenous people of Siberia and the Americas, finding that the latter was colonized in at least three waves. New analyses also show that most Native Americans descended from a group of people who migrated along the coast and sent bands of settlers inland. Linguists reached the same conclusion via comparative studies of native languages.
DNA questions Clovis First
More evidence against Clovis First came from a second study conducted by Jenkins and Willerslev. Mindful of the intense criticism of the Clovis Firsters, Jenkins returned to the Paisley caves in 2009; the team was extra careful. Dressed in bio-hazard suits normally used for working with dangerous viruses, the scientists recovered more than 65 new coprolite specimens and mapped every millimeter of the cave floor, making it one of the best-documented sites in North America. Willerslev again found human DNA in the feces, and after following up with numerous control experiments, the scientists ruled out the possibility that DNA contaminated the coprolites by seeping through the ground.
But the crowning touch was the discovery of an arrowhead in the caves that was found in the same layer as the human coprolites. The artifact was definitively linked to the other finds from the Western Stemmed culture, which was based west of the Rocky Mountains, not in the American Southwest like Clovis. Scientists once thought that the Western Stemmed culture descended from Clovis, but the newest dates show that Western Stemmed may have arrived in North America before Clovis was settled.
Multiple waves of migration
The recent finds provide strong evidence that humans arrived in North America at least 15,000 years ago. However, the land route was blocked by the ice cap at that time, raising the question as to how the first Americans got here.
Although scientists are wary of drawing hasty conclusions, Jenkins thinks that the Western Stemmed people migrated along a coastal route, either by foot or in small boats, while the Clovis people followed an inland route once the ice-free corridor opened up.
The Western Stemmed theory is supported by new data from islands off the coast of Alaska. Plant remains dating to the glacial period indicate that, for at least short periods of time, there was a narrow ice-free passage along the coast. Jenkins speculates that the two cultures originally descended from the same Asian culture and migrated to different parts of America at different times. The latest Paisley discoveries indicate that the cave dwellers were very different from the Clovis people.
“I… get the picture that they are local folks,” Jenkins explains. “Western Stemmed appears to be desert adapted.” Along with ancient plant debris in stone mortars, the content of the feces indicates that the cave dwellers ate a local root vegetable. The latter is particularly interesting because the roots are found six inches below ground and require that the plant be harvested at the right time — knowledge that can only develop when people remain in the same area for generations.
Willerslev is now extracting more DNA from the Paisley coprolites and hopes to sequence an entire genome and reveal exactly who the cave dwellers were. So far, the genetic markers indicate that they were Asians and possibly the ancestors of Native Americans. This conclusion fits with stone tools found in Siberia and East Asia, which may well be the parent technology of Western Stemmed.
The Clovis culture is surrounded by a bit more mystery, since its predecessor has yet to be identified. The evidence may be buried in Alaska, or even Europe, given the resemblance that Clovis tools have to flints from the 20,000-year-old Solutrean culture that was based in modern-day France and Spain. Willerslev hopes to find the answer in DNA from the only known Clovis skeleton in the world, which he is sequencing at the moment. In these old bones, we may finally uncover the truth about how and when the Clovis culture came to America. by DBI