The resurrection is the basis of our faith.  If you don't believe in it, why bother.  The Assumption is a nice devotion, but not central unless you insist that our sinfulness is transmitted sexually, so that the Immaculate Conception is on one end and the Assumption is a consequence of that.  There is testimony for the Resurrection and tradition for the Assumption going back to the Twelve. 

There are historical markers in the theory of original sin and even evidence for Iraqi patriarchs named Adam and Eve, but they are not our first parents and our first parents probably had no concept of sin and certainly performed no act of original disobedience.  Indeed, our first parents were likely Bushmen in the Kalahari Dessert.  The movie The Gods Must Be Crazy showed that at that time, they did not seem to have bought into the culture of original sin.  Sadly, they now live in JoBurg in air conditioned apartments and are thoroughly modern.