Well, accurate fossil dating is important as you can then make a evolutionally tree unlike if you couldn't predict the fossils accurately. This leads to proof of evolution and allows us to hypothesise whether a fossil is a transitional fossil.
I don't think you need to know where modern humans evolved though.
But evidence that we have a common ancestor arrises from transitional form fossils. Genetics could include DNA hybridisation to show how close we are related to other animals.
P.S This is just off the top of my head, don't quote me
P.S.S just found out this is under the Human story elective, i don't do this elective so really don't quote me on this as i am not sure if i covered the right reasons