The short answer

1. Evolution does not in itself rule out a historical Fall, but the actual details of human evolution appear to.
2. The fictitiousness of the Fall of Adam of Eve does not by any means entail there is no need for Christ.

The longer answer

I. Was there a historical Fall?

Although evolution is not in principle inconsistent with the idea that all of humanity descended from one couple, this appears not actually to have happened (see, for instance, Klein et al. 1993). Hence, it is unlikely that there was anything resembling a literal Fall, unless it potentially involved thousands of people at once rather than a single couple.

II. Does “no Fall” mean “no need for Christ?”

Assuming that people sin and that Christ is the only one who can redeem people from their sins, there would seem to be a need for Christ whether or not there was a literal Fall. What difference would it make whether or not one’s distant ancestors sinned? One can even reconcile the myth of the Fall with science by understanding the myth as an allegory for the tendency (or inevitability, if you wish) of people to sin. Whether one ought to understand the Fall this way is another question, but it certainly seems a more reasonable move than to reject science. Either way, the need for Christ does not hang in the balance—it stands or falls on philosophical and theological grounds, not scientific ones.

References

Klein J, Takahata N, Ayala FJ. 1993. MHC Polymorphism and human origins. Scientific American 269(6): 78-83.