Abundance distributions of large mammals are underused in exploring how ecological pressures vary across contemporaneous sites in the fossil record. To investigate variation in relative abundance across contemporaneous Pliocene mammal communities, we examine the time interval between ∼3.6 and 3.22 Ma at four sites in the Afar and Turkana basins: Hadar and the lower Omo Valley in Ethiopia and East Turkana and West Turkana in Kenya. Taphonomic and collection biases are examined using skeletal parts, body size, and taxonomic data from database collections. Taphonomic biases due to geologic conditions and fossil collection affected all sites, but those in the Turkana Basin appeared particularly affected by collecting bias. As a result, hominin relative abundance is calculated separately using a taphonomic control taxon, which shares similar collection biases and size. Comparisons of mammalian taxonomic groups revealed that the Omo region was dominated by suids and cercopithecids. The other sites are dominated by open habitat and mixed habitat associated bovids. Hominins had higher abundance wherein the dominant mammal taxa indicate a mix of woodland and grassland environments (Hadar) and were rarer at sites where the majority of taxa are associated with woodland vegetation (the Omo Valley). West Turkana is characterized by mixed habitats and the highest relative abundance of hominins relative to control taxa, but sampling issues due to the collection and reporting of papionins likely drive this result. East Turkana has few hominins relative to the control taxon and has dominant habitats indicative of floodplain grasslands but has a small sample size compared with the other sites. These analyses suggest that Kenyanthropus platyops and Australopithecus afarensis inhabited similar types of habitats across different rift basins. Most convincingly, this study contributes to a growing body of evidence suggesting that early hominins diverged from their great ape counterparts by abandoning woodland-dominated habitats.

在探索化石记录中不同时期生态压力如何变化时，未充分利用大型哺乳动物的丰度分布。为了调查上新世同期哺乳动物群落相对丰度的变化，我们研究了阿法尔和图尔卡纳盆地的四个地点：埃塞俄比亚的哈达尔和奥莫河下游谷地以及肯尼亚的东图尔卡纳和西图尔卡纳，在约3.6至3.22 Ma之间的时间间隔。使用骨骼部位，体型和数据库集合中的分类学数据检查拼写和集合偏见。由于地质条件和化石收集而造成的塔普科偏见影响了所有地点，但图尔卡纳盆地的那些似乎受到收集偏见的影响特别大。结果，使用Thophonomic Control分类单元分别计算了人源素相对丰度，具有相似的收集偏见和规模。哺乳动物生物分类学组的比较显示，Omo地区以苏打水和蛇皮动物为主。其他地点以开放栖息地和混合栖息地相关的牛科动物为主。人种的丰度较高，其中主要的哺乳动物分类单元表明林地和草地环境混合（哈达尔），在大多数分类单元与林地植被相关的地点（奥莫河谷）较少。西图尔卡纳州的特点是栖息地混合，相对于对照分类单元而言，人类素的相对丰度最高，但由于收集和报告木瓜蛋白酶的采样问题可能会导致这一结果。相对于对照分类单元而言，东特卡纳半岛的人参较少，且具有占主导地位的生境，可指示洪泛草原，但与其他地点相比，样本量较小。这些分析表明肯尼亚阔叶猴和南方古猿在不同的裂谷盆地中居住着相似类型的栖息地。最有说服力的是，这项研究为越来越多的证据做出了贡献，这些证据表明，早期的人猿放弃了以林地为主的栖息地，从而脱离了与它们的大猿猴。