Well there seems to be some science in the dna-activating thought...
Maybe the reptilians/hybrids really can/have learned to control the dna actions?
Anyways, I have read all his books and actually this reptilian theory is not originally his, but was told to him by multiple witnesses on his trips.
Also, Davis is really sound guy, seen him few times and he really can make his case
David's the man!
He's on internet tv EDGE on 23th or 26th Oct
check:
http://www.edgemediatv.com/watchonline.html