Establishing sustainable colonies off Earth would put some of our metaphorical eggs in another basket, and make it more likely that our species could survive a

Establishing sustainable colonies off Earth would put some of our metaphorical eggs in another basket, and make it more likely that our species could survive a major catastrophe. It's something we should be able to do in the next few decades or centuries, and I'm all for it. But given current or reasonably foreseeable technology, we're just not going to be able to ship off enough people to relieve population pressures on Earth. (Question: Has emigration to North America ever made a significant dent in population pressures in Europe, Asia, or Africa?)