I've been doing a lot of work lately on a possibly related branch, the Davison family who came to Pennsylvania before 1700. They were Quakers. There were also Davison family (unrelated) in Virginia before 1700. My earliest documented Davison ancestor is James Davidson-3572 (should be Davison) born 1715. That profile contains some links and info on the Family History project at FTDNA documented on rootsweb, for using yDNA to establish family lines, it sounds like a lot of work has been done with the Davison/Davidson family.