Humans can get factory if they have lab, it's just humans in the game are rather stupid (Like building roads on precious oil, lava, or jungle) or relatively stuck (In an endless loop of harvest bring back eat)
But they didn't build the factory either, even as i had the lab. On the screenshot it's 2 tiles down and 1 tile to the left from the windmill.
From the description of the factory, it needs the market, which is pretty unlucky if it's a "luck" thing mid-game.
PS: Even as i had enough food they didn't build it =( and it's not the fault on my resources. had like 30 of each.