GMAT Sentence Correction (SC) | Re: May and Might; Can and Could

Hi Can anyone explain as to how do we understand the nuances of usages of may & might in different situations :

47.According to scientists at the University of California, the pattern of changes that have occurred in human DNA over the millennia \


(D) indicates that everyone alive today may be a descendant of a single female ancestor who
(E) indicates that everyone alive today might be a descendant from a single female ancestor who