Well, if you look closer and think about it..
Lavos has indirectely harvested humans.
Think about it.
He landed, killing off the reptites. Humans flurished. Then around 3,000,000BC, the Frozen Flame had first contact and everyone started to rapidly evolve.
Then, through their evolution, they gained magic, then lost it.
Then they advanced with technology.
Now all this time, Lavos has been absorbing their DNA and good genes so he could perfect himself. And in the end, he wants to kill them all off so his children can thrive.