But the western coast was not the only available route for early colonists. An ice-free corridor formed after 2 ice sheets that had met in the middle of the continent began to melt. At first, the meltwater formed vast lakes, but these eventually drained, leaving dry land. This corridor ran along the eastern flank of the Rockies, from Alaska to the lower 48 states. It was originally believed to have opened up 13,000 years ago, which fit the Clovis-First scenario, but ruled out it being available for earlier people.
A group of scientists decided to take another look at this corridor, using new methods of dating, and determined that the corridor formed at least 14,000 to 15,000 years ago, possibly more. What's more, the corridor in northern Alberta was at least 400 kilometers wide and no longer held any large lakes. Now, the corridor was scoured by retreating ice and pierced by cold winds, so it would have seemed a formidable place to early travelers. But hunter-gatherers from Beringia may have decided to explore it after watching flocks of waterfowl head south in the fall and return in the spring. Food would have been scarce, but the explorers could have hunted birds or larger game, such as mountain sheep, now believed to have grazed in the Yukon and northern British Columbia.
The travelers may have taken along dogs. Siberian hunters first domesticated wolves as long ago as 33,000 years. These would have made valuable hunting companions and pack animals. A 1994 study revealed that dogs carrying 13 kilograms (28.7 lbs) could travel as far as 27 kilometers a day, in the right conditions. If hunting failed, and starvation threatened, the migrants could have eaten some of their dogs. One scientist calculated the colonists could have reached the southern end of the corridor in only four months, traveling at 16 kilometers a day.
Back at Buttermilk Creek in Texas, the scientists are still studying the tiny, delicate tools created and left by the pre-Clovis people, and may have found new clues about the origins of the Clovis people. 2,500 years after the pre-Clovis people knapped blades and bifaces, Clovis hunters used similar techniques across North America to make massive, elongated blades, some reaching 21 cm (8.3 inches) or more in length. It is possible the Clovis people were descended from earlier migrants coming through Beringia.
https://www.scientificamerican.com/article/the-first-americans/#:~:text=For%20decades%20archaeologists%20thought%20the,thousands%20of%20years%20before%20that.
