Jag tror att detta är Nighteyes , av Garfield Reeves-Stevens. ISBN 978-0553285031.
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Spolare:
The 'aliens' were human time-travelers from the far future. An unspecified calamity (involving massive auroras) had wiped out most of the human population, with only 300 people in the New Zealand area having survived to repopulate. In the future, humanity won a war against the aliens; this is the reason for the quote about there being 'none anymore'. The humanoids in the story consisted of several types (drones, controllers, connections, slights, engineers, soldiers) who were the genetically altered human army that won the war, but they had no reproductive ability and greatly reduced emotional capacity. That is why the future humans were so disciplined and militaristic. They had mastered some forms of unknown physics totally different from what is known today, (using the fundamental principals "transference" and "placement").
The reason they were going back in time to was to gather genetic material, motherly caretakers, and historical artifacts from the world immediately before the cataclysm, whose absence wouldn't be missed (no paradoxes) as it would all have been destroyed in the cataclysm anyway. It's more complicated than that, but that's a good enough summary.