譯/王麗娟
Since 1900, average life expectancy around the globe has more than doubled, thanks to better public health, sanitation and food supplies. But new study of long-lived Italians indicates that we have yet to reach the upper bound of human longevity.
自1900年以來，由於公共衛生、環境衛生和食品供應獲得改善，全球人類的平均壽命增加了一倍有餘。不過，對長壽的義大利人所做的一項新研究指出，人類尚未達到壽命的上限。
"If there's a fixed biological limit, we are not close to it," said Elisabetta Barbi, a demographer at the University of Rome. Barbi and her colleagues published their research Thursday in the journal Science.
羅馬大學人口統計學家伊莉莎貝塔．巴比說：「如果說有固定生物限制的話，我們還未靠近這個上限。」巴比和她的同事周四（七月十二日）於「科學」雜誌發表了他們的研究結果。
The current record for the longest human life span was set 21 years ago, when Jeanne Calment, a Frenchwoman, died at the age of 122. No one has grown older since — as far as scientists know.
現今人類壽命的最高紀錄出現於21年前，這位法國女性珍妮．卡爾蒙122歲時去世。其後，就科學家所知，沒有人比她更長壽。
In 2016, a team of scientists at Albert Einstein College of Medicine in the Bronx made the bold claim that Calment was even more of an outlier than she seemed. They argued that humans have reached a fixed life span limit, which they estimated to be about 115 years.
2016年，紐約市布朗克斯區「阿爾伯特．愛因斯坦醫學院」的一支科學家團隊，大膽宣稱卡爾蒙是個十分異常的特例。他們說，人類已到達固定壽命的上限，估計這個上限約是115歲。
A number of critics lambasted that research. "The data set was very poor, and the statistics were profoundly flawed," said Siegfried Hekimi, a biologist at McGill University.
一些批評者對那項研究發出抨擊。 麥吉爾大學的生物學家齊格佛里德．希基米說：「數據集很差，統計數字存在嚴重缺陷。」
Anyone who studies the limits of longevity faces two major statistical challenges.
任何研究壽命極限的人均面對兩大統計上的挑戰。
There aren't very many people who live to advanced ages, and people that old often lose track of how long they've actually lived. "At these ages, the problem is to make sure the age is real," Barbi said.
不是很多人能活到高齡，而那麼長壽的人通常已記不清楚他們真正的歲數。巴比說：「到了這等年歲，最大問題在於確保年齡的真實性。」
Barbi and her colleagues combed through Italy's records to find every citizen who had reached the age of 105 between 2009 and 2015. To validate their ages, the researchers tracked down their birth certificates.
巴比和同事爬梳了義大利的紀錄，找出那些在2009到2015年間，年滿105歲的所有公民。為了驗證他們的年齡，研究人員還追查了他們的出生證明。
The team ended up with a database of 3,836 elderly Italians. The researchers tracked down death certificates for those who died in the study period and determined the rate at which various age groups were dying.
該團隊最終建立了一個由3,836名義大利老人組成的數據庫。這些研究人員追蹤了研究期間去世者的死亡證明，並計算出不同年齡組的死亡速度。
It's long been known that the death rate starts out somewhat high in infancy and falls during the early years of life. It climbs again among people in their 30s, finally skyrocketing among those in their 70s and 80s.
人類早已知道，人類的死亡率一開始在嬰兒期是稍高，到了幼年時會下降。30幾歲時死亡率會再攀升，最後在70幾、80幾時暴升。
If the death rate kept exponentially climbing in extreme old age, then human life span really would have the sort of limit proposed by the Einstein team in 2016.
倘若死亡率在極端高齡者中呈倍數上升，那麼人類壽命可能如愛因斯坦醫學院團隊在2016年所提，真的已來到那種上限。
But that's not what Barbi and her colleagues found. Among extremely old Italians, they discovered, the death rate stops rising — the curve abruptly flattens into a plateau.
不過，巴比和她的同事發現情況並非如此。他們發現，在義大利的極端高齡者中，死亡率停止上升，也就是曲線突然變平，變成了高原。
The researchers also found that people who were born in later years have a slightly lower mortality rate when they reach 105.
研究人員還發現，較晚出生的人，在他們達到105歲後，死亡率略低。
"The plateau is sinking over time," said Kenneth W. Wachter, a demographer at the University of California, Berkeley, who co-authored the new study. "Improvements in mortality extend even to these extreme ages."
柏克萊加州大學的人口統計學家、這項新研究的共同作者肯尼斯．W．華契特說：「高原隨著時間而下降。死亡率的改善甚至延伸到這些極端高齡者。」
"We're not approaching any maximum life span for humans yet," he added.
他補充說：「我們還沒接近人類的任何最高壽命。」
※說文解字看新聞
文章主要推翻人類壽命（human life expectancy）已達到或已出現上限（limit），約莫是115歲的說法，指出人類尚未達到任何最高壽命（maximum life span），言下之意，隨著條件改善，人類的最高壽命還會繼續上升。
Human life expectancy，human lifespan，human longevity都是「人類壽命」意思，且可相互為用。expectancy（名詞）意為預期、期待，life expectancy 意為預期壽命。lifespan（名詞）也可寫作life span，意為壽命、使用期限、有效期限，span （名詞）在此指一段時間。longevity（名詞）意為壽命或長壽（long life）。
Advanced age（advanced years）意為「高齡」，如advanced age fertility treatment （高齡生育治療），Advanced-age fertility has been increasing。（高齡生育一直在增加）。台灣的高齡產婦（advanced maternal age，高齡懷孕)定義為懷孕時34歲、生產時35歲以上女性，文中的advanced ages 泛指活到高齡的老人。
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