According to scientists at the University of California, the pattern of changes that have occurred in human DNA over the millennia indicate the possibility that everyone alive today might be descended from a single female ancestor who
lived in Africa sometime between 140,000 and 280,000 years ago.Error Analysis:
1. The subject for the plural verb “indicate” is singular “the pattern”. So, we have SV number agreement here.
2. The underlined portion contains “possibility” as well as “might”. Both the words indicate possibility. Hence, we cannot use both the words in same construction. Presence of both renders one of them redundant.
3. Use of “might be descended”. The correct verb here should be “might have descended” because all the alive people today have already taken birth and thus have descended. Verb “might be descended” seems to suggest that this action could have some possibility in the future.POE:
(A) indicate the possibility that everyone alive today might be descended from a single female ancestor who: Incorrect
for the reason stated above.
(B) indicate that everyone alive today might possibly be a descendant of a single female ancestor who had: Incorrect.
1. Same SV agreement number error as in choice A.
2. Same redundancy error as in choice A.
3. Use of past perfect tense “had lived” is incorrect here. There are no two past events that we need to use past perfect tense to establish sequence. The sentence is presenting general information about this woman ancestor and hence, nust be written in simple past tense.
(C) may indicate that everyone alive today has descended from a single female ancestor who had: Incorrect.
1. Placement of “may” is incorrect. Per the original sentence, there is a possibility that all of us have descended from a single woman ancestor. Per this choice the possibility is that the pattern of changes may indicate something. This is certainly not the intended meaning.
2. Same past perfect tense error as in choice B.
(D) indicates that everyone alive today may be a descendant of a single female ancestor who: Correct.
(E) indicates that everyone alive today might be a descendant from a single female ancestor who: Incorrect.
“descendent from” is an incorrect expression.
Hope this helps.