But it doesn't rule out God.

Evil things, as I define them, that is, bad shit humans do, first came into being at the Fall. Before the Fall, humanity lived more or less like animals with tools. We had tribes, clans, family structures, whatever, or maybe we didn't. We definitely had tools, but we primarily employed them for the purpose of hunting, gathering, and simple, non-surplus-producing agriculture. To me, the biblical Fall represents the ancient shift from being subject to God's laws, to trying to make our own. We built cities, learned science, and envisioned ourselves as so loved by God that we were kings over the Earth.

Harm existed before the Fall, and pain, and suffering and selfishness and sadness and whatnot. But it wasn't truly evil until we allowed ourselves to stray so far from Nature that we saw ourselves as immune to God's laws in this lifetime. We still believe(d) that we were subject to God's judgement post-mortem, and that God or god(s) could punish us within this life, but that it was possible to use our intellect and thumbs to circumvent it.

The short answer is that the first evil thing was humanity itself. Or whichever of our primate ancestors was first granted free will and developed morality. Not just because knowing better and doing wrong any way is the first evil thing, but because this creature would set in motion all later evil things.