Emigrants from Siberia that walked across the Bering land bridge into North America may have had dogs in their company, and one writer suggests that the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago, although the earliest archaeological evidence of dog-like canids in North America dates from about 9,400 years ago. What type of working dog may have been the reason so many humans were able to get into North America 12,000 tears ago?