In 802,701, even before revealing to Alex that he remembers everything, Vox makes peculiar quips hinting at this. Whether it's mentioning Jules Verne as right up Alex's alley, or quoting a poet from after his era like T.S. Elliot as someone he wouldn't know yet.
The Über-Morlock letting Alex go with the Time Machine isn't entirely out of civility or some vestigial shred of human empathy. Having not only knowledge of what happened in the past but also a glimpse into Alex's mind, he knows well that whatever happens, he and the Morlocks will still come into existence. Why bother trying to stop the man when victory had already been decided?
Vox spent thousands of years alone in the underground ruins completely alone, save for one Eloi who managed to escape the Morlocks. We then see that the Eloi died of old age and until Alex showed up, Vox was probably going to spend eternity in the same room as his only friend's corpse, all the while unable to bury him.
We only see one attempt to save Emma. How many times did Alex try to save her before he realized that there was no saving her, and needed to find out why?
He says twenty seven.
That one Funny Background Event in 2030 New York, when a teacher scolds one of her students and threatens to "resequence your DNA", becomes less funny when it implies that genetic engineering appears to have made significant advances by that time. Advances that those who fled underground when the Moon blew up took along and developed...and which were likely used later on to breed themselves into the Morlocks. No wonder the Über-Morlock describes himself, and by extension the Morlocks' existence, as being the inescapable result of the kind of reckless progress Alex embodied.
