Metopic suture of Taung (Australopithecus africanus) and its implications for hominin brain evolution
Metopic suture of Taung (Australopithecus africanus) and its implications for hominin brain evolution
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DOI：
10.1073/pnas.1119752109
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发表时间：
2012-05-29
影响因子：
11.1
通讯作者：
de Leon, Marcia S. Ponce
中科院分区：
文献类型：
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作者：
Falk, Dean;Zollikofer, Christoph P. E.;de Leon, Marcia S. Ponce
南方古猿非洲种（Taung）的模式标本包括一个自然的内模，它复制了右脑半球的大部分外部形态，以及一个与内模连接的面部骨骼碎片。尽管Taung在3 - 4岁之间死亡，但内模再现了前沿着中线向嘴侧延伸的清晰额突缝（MS）的小三角形残留物[Hrdlicka A（1925）Am J Phys Anthropol 8：379-392]。在这里，我们描述和解释这一特点的Taung在光的比较化石和现实主义的数据MS关闭的时间。在类人猿中，多发性硬化症通常在出生后不久融合，因此类似于Taung的未融合多发性硬化症是罕见的。然而，在人类中，MS在出生后融合良好，部分或未融合的MS很常见。在大约300万至150万年前的纤细化石成年人中，MS也相对频繁，这表明晚期MS融合的现代人类模式可能在早期人类进化过程中变得适应。有利于延迟融合的选择性压力可能来自围产期个体发育的三个方面：（i）通过为两足动物重新配置的产道分娩大头新生儿的困难（“产科困境”），（ii）出生后早期脑生长率高，（iii）额叶新皮层的重组和扩张。总的来说，我们的数据表明，古人类的大脑进化发生在一个复杂的胎盆约束网络，这需要修改额叶神经颅骨化模式。
The type specimen for Australopithecus africanus (Taung) includes a natural endocast that reproduces most of the external morphology of the right cerebral hemisphere and a fragment of fossilized face that articulates with the endocast. Despite the fact that Taung died between 3 and 4 y of age, the endocast reproduces a small triangular-shaped remnant of the anterior fontanelle, from which a clear metopic suture (MS) courses rostrally along the midline [Hrdlicka A (1925) Am J Phys Anthropol 8:379-392]. Here we describe and interpret this feature of Taung in light of comparative fossil and actualistic data on the timing of MS closure. In great apes, the MS normally fuses shortly after birth, such that unfused MS similar to Taung's are rare. In humans, however, MS fuses well after birth, and partially or unfused MS are frequent. In gracile fossil adult hominins that lived between similar to 3.0 and 1.5 million y ago, MS are also relatively frequent, indicating that the modern human-like pattern of late MS fusion may have become adaptive during early hominin evolution. Selective pressures favoring delayed fusion might have resulted from three aspects of perinatal ontogeny: (i) the difficulty of giving birth to large-headed neonates through birth canals that were reconfigured for bipedalism (the "obstetric dilemma"), (ii) high early postnatal brain growth rates, and (iii) reorganization and expansion of the frontal neocortex. Overall, our data indicate that hominin brain evolution occurred within a complex network of fetopelvic constraints, which required modification of frontal neurocranial ossification patterns.