Ice Age Begins

Colorado’s glaciers began their formation 3 million years ago. This means that large bodies of frozen water existed all along the chain of mountains, the temperature never quite cold enough for them to melt completely. As melting water trickled down slowly, debris like soil and minerals ran down the mountains and into the valleys and rivers, creating hospitable environments for all sorts of animals.

Today, tiny remnants of many of these glaciers still exist. The Front Range, home to modern-day Denver, is considered to be a glacial region. It’s no wonder Denver has been such a popular spot to settle for thousands of years! By studying these glaciers, we gain a better understanding of where animals may have settled and why.

Ice Age Peak

In many of these glacier deposits, ice melted enough to create caverns and holes large enough to fill up as lakes. Because of this, many massive animals found homes in these rich environments. Ancient Colorado was home to mammoths and mastodons, who were both relatives of modern day elephants. Where mountain towns like Aspen, Vail and Glenwood now sit, you could also once find ground sloths and camels. As time went on, many of these animals, like camels, sloths and armadillos migrated further south to warmer regions, to the point where many of their modern-day counterparts are only found in South America. However, some of the thickest-coated of these animals like bison and bears continued to thrive in Colorado. Since these animals lived much more recently than dinosaurs and the Earth in which their fossils are found, minus some ice melt, has moved around very little, scientists have found many fossils in great condition. By observing the placement and markings on these  fossils – such as tusks, teeth and other bones —  we can pinpoint almost exactly where these animals roamed, who they hunted, who they were hunted by, and even how long they lived.

It’s unknown why so many of these large animals, known as megafauna, found a home in Colorado, but it’s thought that the climate was perfectly warm enough during this period of the Ice Age that these animals could live comfortably at high altitudes year-round – and plants could thrive. It’s also unknown why so many of these ancient animals were so large compared to their modern day counterparts. Scientists theorize that it could be due to a larger concentration of oxygen in the atmosphere or simply more space for these animals to grow – after all, cities’ didn’t exist back then. More than likely, it’s because the colder climate meant that animals needed to evolve larger masses of thick fur or muscle to keep body heat, and when the Ice Age finally began to end, that adaptation wasn’t needed anymore.

First Humans

Just like the rest of the Americas, the first humans in Colorado came via the Bering Land Bridge, a once-extant straight that connected Russia to Alaska. Based on evidence from Mammoth hunting sites on the eastern plains of Colorado, it’s likely that the first residents of the Front Range came here between 18,000 and 13,000 years ago – that’s over 11,000 years before the European “discovery” of North America! These ancient humans took advantage of the megafauna of Colorado,, hunting mammoths, mastodons and gomphotheres (another relative of elephants) using specialized tools they made out of stone. They roamed around the plains and Eastern Rockies and left plenty of evidence of their nomadic existence, such as campfires, arrowheads, burial sites, and mud-covered huts.

Since they left no writing behind and because it was so long ago, it’s difficult to know exactly how these people lived. The greatest clue we have are their arrowheads, known as Clovis points. These were often attached to sticks and were the primary tool for hunting large animals. Since these animals roamed across hundreds of miles for their own survival, it’s more than likely that humans had to do the same as they followed these animals. We have uncovered evidence of humans existing all across the Front Range, never settling in one specific spot or building towns. We don’t know how often they moved around, but with the ability to hunt animals from all over and evidence that they trained ancient relatives of modern-day pet dogs for navigation, we can assume that they were comfortable travelling thousands of miles over their lifetimes to ensure their own survival.

Proto-Tribes

As the Ice Age  came to a natural end and a warmer climate came about, the large animals that thrived during the period either died out or migrated elsewhere. Only modern big animals like bison, moose, bighorn sheep and bears remained. Additionally, the warmer climate meant that wild plants diversified. Thus, human society transitioned to something more agrarian, meaning they relied on smaller animals and plant-based diets. Through this, people lived in smaller tribes and cultivated resources, creating true settlements for the first time. These became the foundations for the highly connected and resourceful Native American tribes that exist to this day.