Wouldn't those examples be natural selection, not evolution?
Natural selection works on the range of variation within a population.
That range of variation is supported by mutations.
If a change, say in climate, occurs, one end of a range (for example, skin color) may be slightly favored over the other end. Hot climate favors darker skin, low sunlight favors lighter skin up to a point.
Over time the range of variation within that trait expands again (its like a bell curve). In this way populations can adapt to changing conditions, as long as conditions don't change too fast.
This change over time is called evolution.
...or simple adaptation...
I don't think you know what you're talking about.
Evolution = variation + selection
I gather you accept selection. Do you think variation does not exist?