No reason that 7 billion humans can't work towards both at the same time. Many technologies (like cheap, reusable heavy-lift rockets) will be useful for both. B

No reason that 7 billion humans can't work towards both at the same time. Many technologies (like cheap, reusable heavy-lift rockets) will be useful for both. Bezos seems interested in the Moon and Musk in Mars, but I don't think you would hear either of them saying one place must have a colony before starting to work towards the other. Let a thousand flowers bloom.