47
(A)Then the view switched to genes.
(B)Now some of the other candidates have begun to emerge.
(C)Life spans are nothing like a trait such as height, which is mainly inherited.
(D)So these days, when it comes to life span, many people try to think of some long-lived family members.

The scientific view of what determines a life span [1]or how a person ages has swung[2] back and forth. First, a couple of decades ago, the emphasis was on environment, eating right, exercising, and getting good medical care. 47 It is the idea that you either inherit the right combination of genes that will let you eat fatty steaks and smoke cigars and live to be 100, or you do not. And the notion has stuck[3]. 48 If they can come up with an ancestor or two who lived a long life, they assume they have a genetic gift for longevity. But recent studies find that genes may not be so important in determining how long someone will live and whether a person will get some diseases—except, perhaps, in some exceptionally long-lived families. 49 The likely reason is that life span is determined by such a complex mix of events that there is no accurate predicting for individuals. The factors include genetic predispositions[4], disease, nutrition, a woman’s health during pregnancy, and subtle[5] injuries and accident. 50 The result is that old people can appear to be struck down for many reasons, or for what looks like almost no reason at all, just chance.

47
（A），那麼該視圖切換到基因。
（B）現在有一些其他的候選人已經開始出現。
（C）壽命都像一個特徵，如身高，這主要是繼承。
（D）因此，這些天，當涉及到壽命，很多人都試著想一些長期存在的家庭成員。

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