這個句子著實理解起來有難度——但還是可以理解的：
句子成分劃分：
However,【whether such a sense of fairness evolved independently in capuchins and humans,or whether it stems from the common ancestor that the species had 35 million years ago,主語從句】【is謂語 】,as yet,【an unanswered question表語】.
主語從句成分：
However,whether 【such a sense of fairness 主語】【evolved independently in 謂語】【capuchins and humans賓語】,or whether 【it 主語】【stems from謂語】【 the common ancestor that the species had 35 million years ago賓語】,is ,as yet,an unanswered question.
的確,兩個句子謂語動詞時態(tài)不一致.但是,這可能正好與句子要表達(dá)的意義對應(yīng)——
evolved independently in 在當(dāng)時從、、、、、、演變過來
stems from "源于 ":經(jīng)常采用【一般現(xiàn)在時】.因為,所陳述內(nèi)容可以看做是客觀事實.類似詞還有date back/date from 追溯到；始于；起源于.例如：
.It actually does a whole bunch of things,but one thing it does,I think,is try to answer that question,and to assert that evil stems from human behavior.
它其實有很多意義,但我覺得,其中之一就是解答這個問題,并且聲稱邪惡來自人類行為.
And it stems from an obvious projection of the Protestant- Catholic tension onto Israelite history.
它起源明顯的規(guī)劃,是清教-,與天主教的緊張關(guān)系在以色列歷史中的體現(xiàn).