Schroeder Lauren, Ackermann Rebecca Rogers
Human Evolution Research Institute, University of Cape Town, Rondebosch 7701, South Africa; Buffalo Human Evolutionary Morphology Lab, Department of Anthropology, University at Buffalo, SUNY, Buffalo, NY 14261, USA; Department of Archaeology, University of Cape Town, Rondebosch 7701, South Africa.
Human Evolution Research Institute, University of Cape Town, Rondebosch 7701, South Africa; Department of Archaeology, University of Cape Town, Rondebosch 7701, South Africa.
J Hum Evol. 2017 Oct;111:1-17. doi: 10.1016/j.jhevol.2017.06.004. Epub 2017 Jul 27.
Recent fossil finds have highlighted extensive morphological diversity within our genus, Homo, and the co-existence of a number of species. However, little is known about the evolutionary processes responsible for producing this diversity. Understanding the action of these processes can provide insight into how and why our lineage evolved and diversified. Here, we examine cranial and mandibular variation and diversification from the earliest emergence of our genus at 2.8 Ma until the Late Pleistocene (0.126-0.0117 Ma), using statistical tests developed from quantitative genetics theory to evaluate whether stochastic (genetic drift) versus non-stochastic (selection) processes were responsible for the observed variation. Results show that random processes can account for species diversification for most traits, including neurocranial diversification, and across all time periods. Where selection was found to shape diversification, we show that: 1) adaptation was important in the earliest migration of Homo out of Africa; 2) selection played a role in shaping mandibular and maxillary diversity among Homo groups, possibly due to dietary differences; and 3) Homo rudolfensis is adaptively different from other early Homo taxa, including the earliest known Homo specimen. These results show that genetic drift, and, likely, small population sizes were important factors shaping the evolution of Homo and many of its novel traits, but that selection played an essential role in driving adaptation to new contexts.
最近发现的化石凸显了我们人类属（Homo）内部广泛的形态多样性以及多个物种的共存。然而，对于产生这种多样性的进化过程却知之甚少。了解这些过程的作用有助于深入了解我们的谱系如何以及为何进化和多样化。在这里，我们研究了从280万年前我们人类属最早出现到晚更新世（12.6万 - 1.17万年前）期间颅骨和下颌骨的变异与多样化情况，使用基于数量遗传学理论开发的统计测试来评估随机（遗传漂变）与非随机（选择）过程是否导致了观察到的变异。结果表明，随机过程可以解释大多数性状的物种多样化，包括脑颅多样化，并且在所有时间段都是如此。在发现选择塑造多样化的地方，我们表明：1）适应在人类最早迁出非洲的过程中很重要；2）选择在塑造人类群体下颌骨和上颌骨的多样性方面发挥了作用，这可能是由于饮食差异；3）鲁道夫人（Homo rudolfensis）在适应性上与其他早期人类分类群不同，包括最早已知的人类标本。这些结果表明，遗传漂变以及可能的小种群规模是塑造人类及其许多新性状进化的重要因素，但选择在推动对新环境的适应方面发挥了至关重要的作用。
