Reconstructing Evolutionary Adaptive Paths (REAP) is one of several methods to improve enzyme -functionality. This approach incorporates computational and theoretical aspects of protein engineering to create a focused library of protein variety with a high degree of functionality. In contrast to other -techniques like DNA shuffling, REAP allows a library to have diverse functionality among relatively few variants. REAP is a low-throughput method which takes advantage of natural selection and uses ancestral protein sequences to direct gene mutations, thereby creating a library with a high density of viable proteins. These proteins must then be assayed to characterize their functionality to identify which variants have the desired traits such as acid stability or thermostability.