Instincts

It took him a while to get used to being around humans again. Not that it was so long in his no-longer-new sense of time, but compared to the lives of the human lifespans surrounding him it was.

It had been far easier to adapt to living on his own, a solitary hunter in the wilderness. There hadn't been very many long spans of time in which to think, and if he spent a while singing every song he could remember or arguing with friends he wished he could hallucinate so he'd have company, the animals weren't going to care except for about how noise meant he was probably easy prey.

When he had returned to civilization, if it could truly be called civilization when language was still a relatively new thing, he'd found it hard to act according to even the skimpy social norms that they had had at the time. His usual behaviors had been trained into him over millions of years, and it was hard to break habits even when they weren't so firmly established. So he was sure they spoke of him behind his back as the twitchy (because how could he not be twitchy when there were a million things around him that were just wrong to his learned instincts?) weird (he could live with this description; he'd been weird his whole life, even if for most of it there wasn't anybody to call him it) guy. That description, obviously, didn't make anybody truly happy to have him around, but if there was one thing he'd learned in his millennia of life, it was how to hunt, and hunting was of major importance if they wanted to live.

By the time things got a little more organized (and he'd traveled around a bit, because somebody not aging was a bit suspicious, especially with such short lifespans as people had) he'd managed to retrain himself to be less twitchy and weird and blend in a bit more. He could hide his weirdness entirely if he wanted to, although that was always boring. He'd always be twitchy, because his hunting instincts weren't the kind of thing he could get rid of, even if he wanted to. But it was useful to know when somebody or something came up behind him, or on his blind side, even if it made him more likely to draw weapons when startled.

He wasn't startled often anymore; the solitude had honed and trained his senses enough that most of the time he could tell exactly what was going on around him without more of a clue than a slight noise.