Bev Stayart wrote: but the first immigrants from Siberia to North America arrived only 12,000 to 14,000 years ago. What is the explanation for this gap of approximately 25,000 years?
One explanation is that the 12,000-14,000 assumption is wrong. I don’t know of any dog remains in the two dozen or so “pre-Clovis” sites of human occupation in both North and South America; maybe they exist, maybe not. But there are lots of more or less reputable anthropologists who don’t believe the Clovis people were the first people in the Americas; and some don’t believe they first moved into this hemisphere from the northwest, either.
Be that as it may, the theory and discussion about dogs and hyenas is interesting (if a little gruesome).
This “first Americans” topic is in continual flux, and many who are working in it are hot dogs, amateurs, etc. But not all hot dogs and amateurs are mistaken; and not all cherished notions of 19th century natural science are correct.
I’ll throw in a Wikipedia article with a bunch of useful links (and an interesting map). You don’t have to believe in Wikipedia to find it useful for the kind of topic-hopping that makes Saponitown such a fun place… for starters, scroll down to External Links and click on the NOVA program; on that page, in the Interactives, click on Before Clovis — etc.
http://en.wikipedia.org/wiki/Meadowcroft_Rockshelter