[gambiting]

65% of humans have lactose intolerance, so depending on where exactly you teleport them to it might be a completely normal thing. I'd imagine the immune system will have the capacity to develop in the same way too, so really it should work out fine.

[dillydogg]

As an immunologist, I see no reason why the newborn from tens of thousands of years ago wouldn't be perfectly suited for the modern world.