Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like.
Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like.
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地猿的犬类性别二态性几乎与人类相似。
DOI：
10.1073/pnas.2116630118
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
White T
中科院分区：
文献类型：
--
作者：
Suwa G;Sasaki T;Semaw S;Rogers M;Simpson S;Kunimatsu Y;Nakatsukasa M;Kono RT;Zhang Y;Beyene Y;Asfaw B;White T
化石中的身体和犬类大小二态性为人类进化的社会行为假设提供了信息，并且自达尔文对这一主题的著名反思以来一直引起人们的兴趣。在这里，我们收集了人类进化枝犬科动物化石的大型数据集，包括从埃塞俄比亚中阿瓦什和戈纳研究区发现的所有可用的地猿化石，并系统地研究了犬科动物在进化过程中的二态性。特别是，我们应用贝叶斯概率方法来减少估计弱和中等二态性水平时的偏差。我们的结果表明Ar。 ramiduscanine二态性明显弱于倭黑猩猩，倭黑猩猩是现存类人猿中二态性最弱、行为上攻击性最小的。 Ar 中犬科动物的平均雄性与雌性尺寸比率。在现代人类群体的变异范围内，上犬齿和下犬齿的 ramidus 估计分别为 1.06 和 1.13。 Ar 的下犬齿大小二态性略大于上犬齿。 ramidus 似乎与早期南方古猿共有，这表明雄性犬齿的减少最初在行为重要的上犬齿中更为先进。现有的化石证据表明，在Ar之前，雄性犬科动物的体型急剧缩小。 ramidus 和人类分支中最早已知的成员，此后犬科动物的二态性水平几乎没有变化。这种进化模式表明，在人类进化早期，与相对较弱的雄性攻击性水平相关的深刻的行为转变，这种模式随后被南方古猿和智人所共享。
Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution and have been of interest since Darwin’s famous reflections on the subject. Here, we assemble a large dataset of fossil canines of the human clade, including all availableArdipithecus ramidusfossils recovered from the Middle Awash and Gona research areas in Ethiopia, and systematically examine canine dimorphism through evolutionary time. In particular, we apply a Bayesian probabilistic method that reduces bias when estimating weak and moderate levels of dimorphism. Our results show thatAr. ramiduscanine dimorphism was significantly weaker than in the bonobo, the least dimorphic and behaviorally least aggressive among extant great apes. Average male-to-female size ratios of the canine inAr. ramidusare estimated as 1.06 and 1.13 in the upper and lower canines, respectively, within modern human population ranges of variation. The slightly greater magnitude of canine size dimorphism in the lower than in the upper canines ofAr. ramidusappears to be shared with earlyAustralopithecus, suggesting that male canine reduction was initially more advanced in the behaviorally important upper canine. The available fossil evidence suggests a drastic size reduction of the male canine prior toAr. ramidusand the earliest known members of the human clade, with little change in canine dimorphism levels thereafter. This evolutionary pattern indicates a profound behavioral shift associated with comparatively weak levels of male aggression early in human evolution, a pattern that was subsequently shared byAustralopithecusandHomo.