Board Thread:Warhammer 40k General Discussion/@comment-6589306-20130228113457/@comment-6078851-20140901135843

i'm afraid prometheus negates that idea - we see the entire evolution of the xeno's from liquid bio-matter to the black-carapaced instectoid biped. the speed of xeno evolution makes me think it would be more likely that tyranids could evolve from xeno's rather that xeno's being created by tyranids.

also tyranids do send scouts to other galaxies, thousands of years in advance, in preperation for consumption, and those scouts are genestealers :)