So what made the changes?Possible, but rare. Much more common is the examination of DNA and matching DNA with similar species to determine placement within the Tree of Life.
Skunks are closely related to Weasels and other small carnivores which commonly have strong smelling scent glands where Skunks have their defensive glands. Scent glands are reasonably common in mammals, and often used to mark territories.
Scent glands are modified sweat glands, and sweat glands are ubiquitous among land mammals.
rossum
Why?
When?
How?
And how do you answer any of these without seeing a specific design form?