Board Thread:Warhammer 40k General Discussion/@comment-192.138.62.36-20140116164341/@comment-6078851-20140212130925

while possible it's extremely unlikely that tyranids were created by the old ones. tyranids can only travel between galaxies at sub-light speed - they apparently have bio-ships that can manipulate the gravity of stars which grants them ftl capabilities, but as there are no stars in the void this ability is rendered useless - thus they have to traverse the void at an unfathomably slow rate. the speed that they're limited to in intergalactic travel infers, in my opinion, that they pre-date the old ones by a significant degree.