Nature：牙齿钡含量是灵长类断奶年龄的一个标记

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断奶是任何哺乳动物（尤其是人类）生命中的一个关键时期，断奶较早可以让妇女在较短时间内生更多孩子。因此，早期断奶的形成有可能对“智人”的演化和成功产生过深远影响。此前，人们一直不能比较准确地从化石确定断奶的年龄，但Manish Arora及其同事在这项研究中发现，牙釉质中的钡-钙比例是人类和猕猴哺乳期的一个可靠标记。

钡含量在哺乳期升高，在断奶时突然降低。对来自一个保存完好的比利时“尼安德特人”的一颗牙齿所做的研究，显示了完全进行母乳喂养（哺乳）的时期和接受混合饮食的时期的时间长短以及一个非常早的断奶年龄——只有大约14个月。（生物谷Bioon.com）

生物谷推荐英文摘要：



Nature       doi:10.1038/nature12169

Barium distributions in teeth reveal early-life dietary transitions in primates

Christine Austin, Tanya M. Smith, Asa Bradman, Katie Hinde, Renaud Joannes-Boyau, David Bishop, Dominic J. Hare, Philip Doble, Brenda Eskenazi & Manish Arora

Early-life dietary transitions reflect fundamental aspects of primate evolution and are important determinants of health in contemporary human populations. Weaning is critical to developmental and reproductive rates; early weaning can have detrimental health effects but enables shorter inter-birth intervals, which influences population growth. Uncovering early-life dietary history in fossils is hampered by the absence of prospectively validated biomarkers that are not modified during fossilization. Here we show that large dietary shifts in early life manifest as compositional variations in dental tissues. Teeth from human children and captive macaques, with prospectively recorded diet histories, demonstrate that barium (Ba) distributions accurately reflect dietary transitions from the introduction of mother’s milk through the weaning process. We also document dietary transitions in a Middle Palaeolithic juvenile Neanderthal, which shows a pattern of exclusive breastfeeding for seven months, followed by seven months of supplementation. After this point, Ba levels in enamel returned to baseline prenatal levels, indicating an abrupt cessation of breastfeeding at 1.2?years of age. Integration of Ba spatial distributions and histological mapping of tooth formation enables novel studies of the evolution of human life history, dietary ontogeny in wild primates, and human health investigations through accurate reconstructions of breastfeeding history.