Kimbel William H, Lockwood Charles A, Ward Carol V, Leakey Meave G, Rak Yoel, Johanson Donald C
Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, 80287-4101, USA.
J Hum Evol. 2006 Aug;51(2):134-52. doi: 10.1016/j.jhevol.2006.02.003. Epub 2006 Mar 6.
We tested the hypothesis that early Pliocene Australopithecus anamensis was ancestral to A. afarensis by conducting a phylogenetic analysis of four temporally successive fossil samples assigned to these species (from earliest to latest: Kanapoi, Allia Bay, Laetoli, Hadar) using polarized character-state data from 20 morphological characters of the dentition and jaws. If the hypothesis that A. anamensis is ancestral to A. afarensis is true, then character-state changes between the temporally ordered site-samples should be congruent with hypothesized polarity transformations based on outgroup (African great ape) conditions. The most parsimonious reconstruction of character-state evolution suggests that each of the hominin OTUs shares apomorphies only with geologically younger OTUs, as predicted by the hypothesis of ancestry (tree length=31; Consistency Index=0.903). This concordance of stratigraphic and character-state data supports the idea that the A. anamensis and A. afarensis samples represent parts of an anagenetically evolving lineage, or evolutionary species. Each site-sample appears to capture a different point along this evolutionary trajectory. We discuss the implications of this conclusion for the taxonomy and adaptive evolution of these early-middle Pliocene hominins.
我们通过对归属于这些物种的四个按时间顺序排列的化石样本（从最早到最晚：卡纳波伊、阿利亚湾、莱托利、哈达尔）进行系统发育分析，检验了上新世早期南方古猿湖畔种是阿法南方古猿祖先的假说，分析使用了来自齿列和颌骨20个形态特征的极化特征状态数据。如果湖畔种是阿法南方古猿祖先的假说是正确的，那么在按时间顺序排列的地点样本之间的特征状态变化应该与基于外类群（非洲大猿）情况的假定极性转变一致。最简约的特征状态进化重建表明，正如祖先假说所预测的那样，每个人科动物操作分类单元仅与地质年代更年轻的操作分类单元共有衍征（树长=31；一致性指数=0.903）。地层数据和特征状态数据的这种一致性支持了湖畔种和阿法南方古猿样本代表一个前进演化谱系或进化物种的部分的观点。每个地点样本似乎捕捉到了这条进化轨迹上的不同点。我们讨论了这一结论对这些上新世早期至中期人科动物的分类学和适应性进化的影响。
