I have read lots on this subject over the last 40 years...  In human
abductions in most cases these faux aliens were taking tissue samples,
doing medical experiments, often on pregnant women.
 This sort of thing along with cattle mutilations all seem to be
tissue harvesting for some sinister purpose.
   There are quasi human occultic groups that do these things to
animals as part of their religious practices.   However, It has been
my conclusion that these fallen angels  are harvesting human and
animal tissue to re-create  a new improved modern and updated 
version of their nephilim cyborgs... Think the spooky "Greys" for
example Since only God can create life that can naturally have
offspring / children if you will, it may well be necessary for the
fallen angels to replace their army of nephilim every so often.
   As we all believe that the final battle is imminent, these faux
aliens must be very busy creating bodies to be inhabited by the
disemboided spirits of the nephilim that we call demons.
   There is  some UFO literature to suggest that some of these Faux
aliens  are impregnating women then taking their unborn children to be
used in their program.
   The  gruesome eternal fate of the fallen angels who mated with
human women before the flood may have kept these  fallen angels from
doing the same thing today.  So they are resorting to creating cyborgs
like the greys and others as well.
   I have been of the opinion that these modern nephilim walk among us
openly today.   My final thought is that all nephilim are bolshevik
liberals... however I'm not yet sure if all liberals are nephilim! Yes
that was a parting joke...  well kinds sorta anyway... Imho most of
the  pathological psycopathic bolsheviks who walk among us are indwelt
by the spirits of the ancient nephilim. So for all practical purposes
they are nephilim...
Lewis