We have seen that modern humans have been in Europe for at least 40,000 years and in Africa for even longer. Humans also occupied Asia, Siberia, and Australia during the Pleistocene as well. But what about North and South America— the “Americas”? Were people here in what is today New Mexico during the Pleistocene? The question of when and how people got to the Americas is not a new one and is the source of continued debate, in which the state of New Mexico figures prominently.
The Earliest People in New Mexico
New Mexico, as it turns out, is world-famous for its pivotal role in understanding how people got to the Americas—sometimes referred to as the “peopling of the Americas.” Influential osteologist (human bone specialist) Aleš Hrdlička was certain that people had only been in the Americas for a few thousand years. This issue, like so many in archaeology, was not purely academic. In the 1800s, North American natives were often depicted by European colonizers as relative newcomers to the Americas. These presumed barbaric newcomers were thought to have cast out a former glorious “race,” who had built the impressive monuments that archaeologists encountered. This view of native peoples as newcomers fit nicely with the drive to colonize the American West.
Mural at the New Mexico Museum of Natural History. Photo: Sue Ruth
The site that changed the face of American archaeology and contradicted Hrdlička’s ideas is called the Folsom site. Like so many significant archaeological discoveries, the Folsom site was found not by a professional archaeologist. Cowboy George McJunkin was searching for lost cattle following a devastating 1906 flood near the town of Folsom in far-northeastern New Mexico when he discovered some odd-looking “cow” bones. These bones turned out to be the fossilized remain of an extinct form of bison called Bison antiquus that lived during the Pleistocene. Later, in the 1920s, excavation at the site revealed humanly made dart points in direct association with the bison. Using the Principle of Association, it was indisputable that people were in North America during the Pleistocene. Like Frere and de Perthes before him in Europe, McJunkin’s find revealed a much deeper time depth to human occupation than was previously accepted.
“Aleš Hrdlička (1869-1943)” by unknown is licensed under public domain.
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Radiocarbon Dating
Early archaeologists had to rely on the Principle of Association, the Principle of Superposition, and with an understanding of soil development rather than techniques like radiocarbon dating to determine how old sites were. Radiocarbon dating had yet to be invented. The technique was developed by Willard Libby and colleagues in 1949, for which he won a Nobel Prize in Chemistry in 1960. Radiocarbon dating takes advantage of isotopes or variants of elements that have different numbers of neutrons. All carbon has 6 protons, but the number of neutrons can vary. Carbon-14 is an isotope of carbon with 6 protons (like all carbon) and 8 neutrons. Adding the number of protons and neutrons (6+8) together yields 14, hence, carbon-14. Radiocarbon dating uses the fact the radiocarbon or carbon-14 is radioactive and decays at a known rate called a half-life of 5,730 years. That known rate of decay is used to estimate how old things are.
So, how does radiocarbon dating work? All living things contain an abundance of carbon-12, a stable isotope that does not decay, and a tiny amount of carbon-14. You, for example, have a small amount of carbon-14 or radioactive carbon. You are slightly radioactive. Once an organism dies, the stable carbon-12 remains unchanged, but about half of the radiocarbon will decay to nitrogen in 5,730 years. Chemists can measure the carbon in an archaeological sample and use the ratio of carbon 12 to carbon 14 to estimate how old something is. The technique has been used effectively for decades and has been refined by comparing the dates to other dating techniques, especially tree-ring dates. Willard Libby, who championed the technique, radiocarbon dated objects of known ages including redwood trees, Egyptian funerary objects, charred bread from the Pompeii eruption, a linen wrap from the Dead Sea Scrolls, all objects with known historical dates to test the efficacy of the method. Libby’s “Curve of Knowns” ushered in a new era in archaeology called the Radiocarbon Revolution. Libby won a Nobel Prize in chemistry for his work.
The Paleoindian Period
The term Paleoindian period is often used to refer to the human occupation of North America during the end of the last ice age. Unlike the Upper Paleolithic of Western Europe, the vast majority of Paleoindian sites are open-air sites, rather than cave sites. Because of this, the preservation of Paleoindian organic remains like shells and bone is scant. A few beads, needles, and other bone artifacts exist, though these are rare. As a consequence, Paleoindian archaeologists have a very little material culture with which to reconstruct the past. The Paleoindian Period is divided into periods based on changes in tools. Once Folsom sites were recognized for what they were, even older sites, called Clovis sites, began to emerge in the archaeological record. Clovis-aged sites are about 13,000 years old and Folsom-aged sites are around 11,500 years old. A “Clovis site” is short-hand for “Clovis-aged site” and refers to any site that dates to the Clovis time period. During the Clovis period mammoth, horses, camels, dire wolves, and other Pleistocene animals roamed North America. Mammoth and bison, and to a lesser extent elk, were the primary targets of Clovis hunters, who likely used atlatls for hunting just like people did in Europe. If you visit the New Mexico Museum of Natural History in Albuquerque, you can see a reconstruction of a Columbian mammoth, a camel, a sabercat, and dire wolves—Pleistocene mammals that were here in New Mexico. The mural on the wall depicts Paleoindian hunters around a mammoth carcass.
A distinct Clovis technology consisted of stone points that are grooved or fluted partway up the point. (Doric Greek columns are also fluted if that helps you remember the term). This fluted technology, as it is called, is unique to the Americas, and occurs nowhere else in the world. Clovis points are diagnostic of the Clovis period, meaning they were unique to this time period. So, if you ever find a fluted point on a leaf-shaped point, it is on the order of 13,000 years old, a very rare and important find.
Another interesting feature of the Clovis period is caches (Kilby and Huckell 2013). Caches are deliberate deposits of artifacts for ritual or functional purposes. A functional cache is simply a cache for a practical purpose. Clovis people may have been placing stone and stone tools in pits in the ground with the idea of returning when they were low on stone and needed to replenish their supplies or raw material. (Stone is often referred to by archaeologists as raw material). Clovis people appear to have been highly mobile and engaged in long-distance trade, as evidenced by their raw material, which can be traced hundreds of miles from their source. Some Clovis caches were potentially ritual in nature, bearing traces of red ocher, the same mineral pigment found in 100,000-year-old caves in South Africa, on Upper Paleolithic Venus figurines, and in ice-age burials of Siberia and Eastern Europe. The Anzick Cache in Montana contained not only red ocher but infant human bones, suggesting the cache was part of a funerary rite and that red ocher had a ritual significance.
Clovis cache by Bill Whittaker is licensed under CC BY-SA 3.0
Extinction of Pleistocene Mammals
One of the most famous Clovis sites called the Blackwater Draw site is located near Portales, New Mexico. The site actually has many different Paleoindian occupations, or episodes of human use, and is open to the public. At the site, you can see the strata of earlier Paleoindian layers at the bottom and later ones at the top. The excavators have preserved a portion of the excavation in situ, so you can see the bones of Pleistocene megafauna in place.
The site of Blackwater Draw also has the earliest human-made wells anywhere, associated with a prolonged drought during the Clovis period. The same drought likely contributed to the demise of the mammoth and other Pleistocene megafaunas like horses, camels, and dire wolves. According to a study by scientists at UNM, the drought was so severe that nothing like it had occurred for at least 40,000 years that they examined. Some argue that drought caused vast habitats of the giant grazing mammals to shrink and fragment, leading to herds dwindling to extinction through lack of forage. During the extinction event, fully 3/4 of all mammalian genera (35 genera) in North America went extinct, including mammoths and mastodons, all camelids (camel species), and horses, all but one species of bison—all within 1000 years of each other. Some larger Pleistocene mammals (including elephants in Africa and bison in North America) became smaller toward the end of the Pleistocene, which is one adaptive response to a reduced food supply.
The stratigraphy at the Blackwater Draw Site. Photo: Sue Ruth
This massive drought in North America appears in the stratigraphy at Clovis sites and is called The Black Mat, which represents the mud at the bottom of a dried-out water source. You can see it clearly at the Murray Springs site in Arizona. Below the mat, there are mammoths, horses, and other Pleistocene megafauna, and above the mat, they do not appear. In fact, Bison antiquus survived the extinction event, but reduced in size in size over to become what we now know (erroneously) as “buffalo.” The climate change hypothesis supporters also point to the fact that megafauna is not the only species of animals that went extinct after the Pleistocene. About 40 percent of small mammals like voles and other rodents, mink, martens, weasels went extinct, as did about 40 percent of mollusk species. Similar extinctions occurred in Europe, northern Asia, and Australia as well. Tropical areas like central Africa and south and Southeast Asia were much less affected—megafauna like elephants and rhinoceros still exist there, at least for the time being.
Another hypothesis for the Pleistocene extinction is the Overkill Hypothesis. The Overkill Hypothesis holds that Paleoindians colonized a continent with numerous mammals that were unfamiliar and unafraid of humans. Secondly, Paleoindians were hunting specialists that concentrated on a few large species which could provide a huge return in meat and fat, but also result in the demise of numerous species. Evidence for megafauna specialization includes, for example, the fact that of the 14 known Clovis kill sites in western and central North America, 11 contain the butchered bones of mammoth or mastodon. Archaeologists Todd Surovell and Nicole Waguespack argue that the number of Clovis elephant kill sites is exceptionally high if you look at elephant kill sites on a global scale. They also argue that human colonization tracks mammoth extinction throughout human prehistory.
Proponents of overkill also point to several other previously unoccupied landmasses of the world where megafauna disappeared simultaneously with the colonization of humans. Australia, for example, was populated with a series of giant species of kangaroos and grazing marsupials that went extinct when humans first colonized the island-continent sometime between 40-60 thousand years ago. On Madagascar, the giant lemur Archaeoindris, about the size of a male gorilla, went extinct around the time that humans reached Madagascar more than 2,000 years ago. New Zealand is another case in point. Several species of giant flightless birds called moas (Dinornithiformes)—some stood up to 12 feet tall and weighed up to 500 pounds—existed in New Zealand before the arrival of the first humans from Polynesia around AD 1250-1300, then became extinct within 200 years of human occupation. One reason for the swift demise is that the native species had no defensive fear of humans and could be easily approached and killed.
Climate change display at the New Mexico Museum of Natural History. Photo: Sue Ruth
The principal weakness of the overkill hypothesis is that there is no direct material evidence for hunting camel, horses, giant beavers, ground sloth, and the like, which all went extinct near the end of the Pleistocene. It is not even clear when some species actually went extinct. Surovell argues that less abundant species, like the American cheetah, are less likely to be found in the fossil record and therefore might falsely appear to go extinct before human arrival.
A combination of the two factors contributing to the demise of megafauna—climate and human predation—is quite possible. Habitat loss due to climate change would have fragmented the large, interconnected populations of steppe animals. Indeed, we know that habitat fragmentation is a key factor in species extinction today. Human hunters could have delivered the final blow by overhunting the dwindling populations that remained.
Folsom
The Folsom period followed the Clovis period and the extinction event, beginning around 11,500 B.P. Folsom hunters focused on Bison antiquus as their main prey. Folsom points are diagnostic of the Folsom time period. Like Clovis points, Folsom points are fluted, but the flute travels the full length of the point. Folsom points also have tiny pressure flakes around the margins of the points and are very thin. These subtle distinctions are important because they indicate the time period of a site. No other points anywhere, at any other time, look like Folsom points. In fact, Folsom points reveal such astonishing craftsmanship, that modern archaeological experimenters, with all our technological improvements, have difficulty replicating them. Indeed, entire conferences have been devoted to understanding Folsom points alone.
Both Clovis and Folsom points are finely made artifacts crafted by skilled knappers. They used the most workable stone material and often chose raw materials with beautiful colors and patterns. In many cases, the raw material came from distant sources. For example, at the Boca Negra Wash Folsom site on Albuquerque’s West Mesa, some of the obsidian (volcanic glass) has been sourced to the Jemez Mountains (Shackley 2016). The chemical procedure used to identify the source is called X-ray fluorescence. Other types of sourcing that involve identifying minerals can also be used to source the stone material.
Sandia Man
We now know that New Mexico has two world-famous Paleoindian sites, the Folsom site and Blackwater Draw (aka the Clovis site). Many people have also heard of another site called Sandia Man Cave located in the Sandia Mountains of Albuquerque. The site was investigated by Frank Hibben who taught anthropology for many years at the University of New Mexico. Hibben’s team found the now-famous Sandia points and claimed that these were stratigraphically below a Folsom level and also older than Clovis. The only other site to produce Sandia points is the Lucy site, also in New Mexico. The site was visited by Hibben himself. Unfortunately, the stratigraphic context at Sandia Cave that Hibben thought was pre-Clovis in age turns out to be hundreds of thousands of years old—much too old for Clovis or Folsom and older even than Blombos Cave in Africa—and not nearly as pristine as Hibben described. Since then, dating problems with all the Sandia point finds have emerged, and unlike Folsom and Clovis, only a handful of Sandia sites, all highly questionable, have been discovered. Today archaeologists universally do not accept the Sandia period or Sandia points.
Surf or Turf? The Peopling of the Americas
As early as the 1500s, speculation began about how people arrived in the Western Hemisphere. José de Acosta (ca. 1540–1600) proposed that there must have been a land bridge connecting the northern reaches of the New World and Siberia. At the time, the geography of this region was completely unknown and unmapped. Much later, it would become clear that a land bridge did indeed exist between Siberia and unglaciated Alaska during cold periods of the Pleistocene called glacials. During glacials, ocean levels dropped as ice sheets on land grew. Note that while the word “ice sheet” suggests a thin layer, ice sheets were as much as a mile thick during the Pleistocene.
This region of exposed land (now submerged and called the Bering Strait) is called Beringia or the Bering Land Bridge. The word “bridge” is also a bit misleading as it implies a narrow strip of land. The Bering Land Bridge was, however, about 1,000 miles north to south at its greatest extent. People could have walked across the Bering Land Bridge from Siberia into the New World following herds of mammoth and bison. Certainly, they wouldn’t have known that they were occupying a region completely uninhabited by people. The land bridge would have been exposed between ca. 30,000 B.P.–10,000 B.P. allowing people to enter during this time frame.
Changing Beringia, Wikimedia Commons. Public domain.
The entering immigrants could, however, go no further than Alaska, because standing in their way were two huge ice sheets, the Laurentide and Cordilleran, blocking entrance into what is today Canada and the lower United States. If people took the land route, they would have had to wait until a warming trend for the ice sheets to melt enough to pass. This warming trend occurred around 13,000–14,000 years ago, creating the Ice-Free Corridor. The opening of the corridor happens roughly at the same time that we see Clovis sites in the United States, around 13,000–13,500 BP.
The Land Bridge Hypothesis has several weaknesses. First, there are no Clovis remains or early fluted points in Alaska. However, a very recent find suggests that people may have been in Canada around 24,000 years ago, putting people in a position to later come down the corridor. Second, there are no early sites in the Ice-Free Corridor. Thirdly, the timing of the opening of the corridor is very close to the time when sites begin to show up in the lower U.S. They would have to really “hustle” to get from Alaska to say, Montana. Finally, there are claims of Pre-Clovis sites that pre-date the opening of the corridor.
Because of these problems, archaeologists began to speculate that people may have come by sea from Siberia. In his book Bones, Boats, and Bison, archaeologist James Dixon proposes that people could have “island-hopped” down the coast of Canada and into the interior. This would help explain the absence of early interior sites as well as the presence of some early coastal sites. We know that people were using boats at this time, because Australia was colonized 50,000 years ago, but was never connected to the mainland by a land bridge—people had to get to Australia by boat. So, theoretically speaking, peopling of the Americas by boat is a possibility.
A third hypothesis suggests people boated across the Atlantic along the ice shelf to the coast of what is today the United States. Popularly called the Iberia, not Siberia Hypothesis, this idea points to similarities in morphology (form) and flint knapping techniques between Upper Paleolithic Solutrean points and Clovis points. This hypothesis suffers from a timing problem (the Solutrean points are 4,000 years earlier than Clovis). And the artwork that characterized the Upper Paleolithic in Europe, like Venus figurines, does not appear in the Americas.
DNA from ancient remains provides some evidence as to the origins of the Paleoindian people. Recently, the DNA of a Clovis child from the Anzick Cache in Montana—the only known Clovis burial—was analyzed. Two types of DNA were analyzed, mitochondrial and nuclear. Mitochondrial DNA is located within the mitochondria and is separate from nuclear DNA in the nucleus of cells. Mitochondrial DNA is passed along only through the mother and so provides a glimpse inside the maternal line of Anzick Boy. Nuclear DNA inside the cell nucleus, in contrast, is a combination of the mother’s and father’s DNA. The results of the DNA analysis reveal Anzick Boy to be most genetically similar to indigenous people of the Americas (especially in Central and South America) with other similarities with modern East Asians and western Eurasians (Rasmussen et al. 2014). The DNA of the Anzick boy, being linked to modern Native Americans and extent Asian populations, does not support the Iberia not Siberia Hypothesis of colonization. After the study was completed, the remains of the child were reburied in Montana according to a ceremony attended by multiple tribes. Though the analysis revealed that Clovis people were related to modern natives peoples of the Americas, many were unhappy with the analysis on principle. Armand Minthorn of the Umatilla Confederated tribes stated, “These are our ancestors’ remains, they are not artifacts. I hope that the people who come after us remember this as well” (Brett 2014). These types of analyses are often the center of ethical debates in archaeology about how to treat both human remains and artifacts. In the next chapter, we will discuss legislation called NAGPRA which addresses this very question.