question: What type of working dog may have been the reason so many humans were able to get into North America 12,000 tears ago ?
answer: sled dogs
turker_answer: Sled dogs may have been the reason so many humans were able to get into North America 12,000 years ago .
rule-based: The may have been reason sled dogs so many humans were able to get into North America 12,000 tears ago .