Early colonists occupied Colorado’s rich and ecologically diverse landscapes in the waning millennia of our planet’s most recent major Ice Age, the Pleistocene, between 14,000 and 12,000 years. Our best-documented evidence for Colorado’s earliest hunter and gatherer inhabitants, people we call Clovis, comes from the Dent site, a naturally exposed bone bed of Late Ice Age and now-extinct Columbian mammoths associated with three stone spear points. The site is situated along the South Platte River on the margins of Colorado’s western high plains.
Discovery and Research
The Dent railroad depot, now demolished, was once located next to the South Platte River southeast of Milliken, Colorado. Railroad tracks serving the depot ran over eroded Ice Age terrace remnants south and west of the river’s modern floodplain. After heavy spring rains in April 1932, railroad foreman Frank Garner noticed very large animal bones eroding from a deep gully draining through a low sandstone bluff west of the tracks. Word of the discovery reached Regis College geology professor and Jesuit priest Conrad Bilgery through one of his students, who was the son of the Dent Depot manager. In September 1932 Father Bilgery excavated some of the bones with his students, identifying them as mammoth. He then contacted Jesse Figgins, paleontology curator at the Colorado Museum of Natural History (now the Denver Museum of Nature and Science).
Figgins delegated further exploration of the mammoth remains to museum staff member Frederick Howarter, who conducted excavations in June and July 1933, with museum volunteers, trustees, Father Bilgery, and his Regis College students. Partial skeletons of five adult female and eight young mammoths were recovered and taken to the Denver museum with two complete Clovis spear points. A third artifact, a broken, upper part of a Clovis point, was kept by its discoverer, railroad foreman Garner, and was given to the museum in the 1950s. At the time, the Clovis culture’s existence was not recognized by archaeologists, although Dent’s projectile points were recognized as belonging to a Late Ice Age (Paleo-Indian) Native American culture.
No further Dent research took place until 1973, when a joint team from the universities of Colorado and Arizona excavated a trench in the earlier bone bed area. The project was to involve two days’ worth of field studies for a University of Colorado student’s doctoral dissertation, but the project was abandoned when it was found that the remaining bones were buried under active railroad tracks.
The team’s trench along the track’s west edge showed that the bones had likely been redeposited from the adjacent bluff draw or washed in from an upstream source. The most deeply buried bones rested on ancient river gravels, showing that the South Platte River once flowed near the 1932–33 bone-bed location. A wood fragment mixed with recovered bone was radiocarbon-dated to AD 1800, indicating that the bone had been historically redeposited from a nearby location. Along with smaller mammoth bone pieces, a young juvenile’s skull was found, indicating the existence of a fifteenth mammoth.
The most recent research at Dent took place between 1987 and 1994. Field studies involved soil sampling cores in the adjacent gully draw, its former bone bed area, and power-driven cores through the railroad bed to surviving bone bed material below. Geologic analysis of an exposed Ice Age terrace near the site and a hand-dug trench in the gully draw were done by University of Northern Colorado (UNC) and University of Arizona (UA) researchers. Other studies analyzed Dent mammoth bones, teeth, and tusks for information on season of death, the mammoths’ social system, and diets as well as Ice Age climate, butchering evidence, chronology, and artifact traits.
Accurate dating of the Dent mammoths’ deaths was not possible at the time of discovery. However, in the past two decades, high-precision radiocarbon dating methods and advanced techniques for dating organic components such as bone and ivory made reliable dating possible. More than a dozen radiocarbon dates were done on Dent bone between 1963 and 2006. In 2006, three high-precision AMS radiocarbon dates on Dent bone provided an averaged calendar-age date of 12,850 years ago.
Research on Dent mammoth bones has been hampered by early dispersal of much of the original collection to out-of-state museums in exchange for other museums’ specimens. On one occasion a complete juvenile mammoth skeleton was assembled from bones of different animals and traded to a Cleveland museum. Modern researchers, in order to access much of the original skeletal collection, have had to travel to multiple museums. Both early (1930s) and more recent skeletal analyses identified a minimum number of fourteen animals. They include an older adult female, four younger adult females, four adolescents, and four younger juveniles and infants. Using modern African elephants for comparison, scientists found Dent’s animals to closely resemble a matriarchal family herd, with young males (bulls) separating from their birth families after maturity.
Dent mammoth bone studies found cut, chop, gouge, and pry marks consistent with carcass defleshing and bone-joint disarticulation. Butchering marks were interpreted as being made when the animals were freshly killed and days to weeks after death. The amount of time between fresh-kill and later butchering episodes is unknown, but season-of-death evidence placed Dent mammoth deaths in late fall to early winter, during which cool or even freezing temperatures would have preserved usable meat for days or weeks. Data from studies of teeth and tusks at the Dent site indicate that the mammoths lived and traveled within a small grazing territory in foothills and plains just east of Colorado’s Front Range.
Geological studies of the 1973 railroad track trench and nearby Ice Age river terrace supported the view that the bone bed’s adjacent draw, which cut through a low sandstone bluff, provided Dent mammoths easy access to water and a shallow river crossing. A UNC excavation in that draw uncovered a narrow gully that the mammoths might have used to descend to the river and where they may have been ambushed, trapped, and killed. The mammoth bones’ relatively unweathered physical condition meant they had not been exposed on the surface for any period of time, suggesting they were buried by sediments, possibly within months to a year after death.
In addition to the butchering marks, evidence of human involvement with the Dent mammoths was found in the form of two intact Clovis spear points and an upper portion of a third point reworked into a hafted knife. One of the points disappeared from the Denver museum collection in the late 1930s or early 1940s. Its location remains a mystery. However, plaster casts and descriptions of the missing point allow detailed reconstruction of its physical traits and tool material. The second point and reworked point/knife are displayed in the museum’s modern Dent exhibit. The three Clovis tools were made from widely dispersed stone sources: northeast Colorado plains Flattop chert, southeastern Wyoming Hartville chert, and a dark gray chert from southeastern Wyoming or the northern Great Plains. Crushed, worn blade edges on all three tools show they were used for heavy-duty cutting of meat and bone.
Colorado’s Dent Mammoth site is one of very few North American archaeological sites with direct evidence of human procurement of extinct Columbian mammoth meat and bone. Deaths of its animals occurred in two or more kill events several days or weeks apart, suggesting ambushes of two herds at different times, or that several animals escaped the earlier ambush only to be ambushed again when they returned to the scene. As is common in prehistoric hunting societies, the Clovis points used to kill the animals were also used in butchering. The scientific evidence from the Dent site shows that Clovis people had a thorough understanding of Colorado mammoths, which made them skilled, successful hunters of the impressive Ice Age mammal.