IMHO, exposing humans and their descendants for life to different conditions of gravity, radiation and overall ecosystem, will make them evolve in ways that will generate a totally different species in very few hundred years.
So it will be just a matter of time, until an orange-colored man with the slogan "Let's make the Earth great again" will want to build a wall between the Earth and Mars (and put it on Mars tab, of course) to avoid that immigrant Martians steal Earthlings jobs.
So a colony in Mars maybe preserves intelligent life with roots in the human species, but I do not think it will preserve the human species as we know it.