> Also, I don't think "always be the case" is a foregone conclusion. Mars' current evolutionary tree isn't looking very good.
I think they mean the opposite of what you inferred; they're saying we'll always need to be lucky to keep surviving, not that we won't need to be lucky to keep surviving after a certain point
by colonizing mars, we split our evolutionary tree more so wiping out 1 branch isn't catastrophic. yes a species has to keep getting lucky to survive. but more branches means more rolls of the dice.
Just because a branch of the evolutionary tree continues does not mean that it will be ours.
Also, I don't think "always be the case" is a foregone conclusion. Mars' current evolutionary tree isn't looking very good.