摘要：2017年5月17日，*學術期刊《Science》旗下《Science Advances》雜志上在線發表了澳大利亞格里菲斯大學Tanya M. Smith研究員的一篇研究論文，論文通過研究猩猩的牙齒，揭示了猩猩長時間吸奶的情況。

2017年5月17日，*學術期刊《Science》旗下《Science Advances》雜志上在線發表了澳大利亞格里菲斯大學Tanya M. Smith研究員的一篇研究論文，論文通過研究猩猩的牙齒，揭示了猩猩長時間吸奶的情況。

研究人員研發了一種方法，它能對靈長類中特別難以捉摸的喂奶方式進行了追蹤，他們用它發現，某些發育未全的猩猩吸奶時間長達8年或以上--這超過了其它非人類靈長動物中所報告的zui長斷奶年齡。這些發現對管理生殖率緩慢低下的瀕危靈長動物(如蘇門答臘和婆羅洲猩猩)頗具意義，因為人們對這些動物的生活史了解甚少。對野生猩猩的斷奶年齡幾無所知，但有些科學家提出，它們在出生后的斷奶所需時間會持續6年之久(或更長)。鋇是一種非必需元素，它在體內的代謝通路常常類似于鈣;當鋇隨母乳一同被攝取后，它很容易進入像牙齒等骨骼組織之中。因此，對這一元素進行測試會是一種提示嬰兒或發育不成熟幼兒是否還在吸奶的有效方法。

在本研究中，Tanya M. Smith和同事對4個猩猩從其出生頭一年便開始分析其牙齒中的鋇含量，從而提供了*如此詳盡的野猩猩吸奶史。他們發現，在出生*年后，牙齒中的鋇濃度通常會降低，但在其8歲和9歲時鋇會一直存在于牙齒之中。此外，作者發現，牙齒中鋇濃度會年復一年地出現高低周期性變化。他們指出，牙齒中鋇濃度下降時期可能對應于水果獲取量大的時候，這時，正在生長的猩猩對奶汁的依賴度較小，而牙齒中鋇濃度的增加則是因為奶攝取量增加的結果，它發生在食物時，那時正在長身體的猩猩需要多吸奶才能維持生長。對猩猩的喂奶和斷奶模式有所了解是有價值的，因為要觀察生活在樹上且不顯眼的猩猩的吸奶情況總是具有挑戰性的。

原文摘要：Nursing behavior is notoriously difficult to study in arboreal primates, particularly when offspring suckle inconspicuously in nests. Orangutans have the most prolonged nursing period of any mammal, with the cessation of suckling (weaning) estimated to occur at 6 to 8 years of age in the wild. Milk consumption is hypothesized to be relatively constant over this period, but direct evidence is limited. We previously demonstrated that trace element analysis of bioavailable elements from milk, such as barium, provides accurate estimates of early-life diet transitions and developmental stress when coupled with growth lines in the teeth of humans and nonhuman primates. We provide the first detailed nursing histories of wild, unprovisioned orangutans (Pongo abelii and Pongo pygmaeus) using chemical and histological analyses. Laser ablation inductively coupled plasma mass spectrometry was used to determine barium distributions across the teeth of four wild-shot individuals aged from postnatal biological rhythms. Barium levels rose during the first year of life in all individuals and began to decline shortly after, consistent with behavioral observations of intensive nursing followed by solid food supplementation. Subsequent barium levels show large sustained fluctuations on an approximay annual basis. These patterns appear to be due to cycles of varying milk consumption, continuing until death in an 8.8-year-old Sumatran individual. A female Bornean orangutan ceased suckling at 8.1 years of age. These individuals exceed the maximum weaning age reported for any nonhuman primate. Orangutan nursing may reflect cycles of infant demand that relate to fluctuating resource availability.