One of the main bits of evidence for Wolpoff's multi-regional hypothesis (that is, the theory that races originated early, before we were Homo sapiens but rather while we were Homo erectus) was the fact the Peking Man from 400,000 years ago also had shovel incisors. That's why this was so important to the researchers: if they could show that shovel incisors were "only" 35k years old, then the Peking Man similarity could be marked up to a coincidence.
But this begs another question. If American indians are descendents of east Asians then why don’t they have shovel incisors? (or do they?)