Data from: Evidence for a Late Pliocene faunal transition based on a new rodent assemblage from Oldowan locality Hadar A.L. 894, Afar Region, Ethiopia

The time interval between 3-2 Ma marks several important transitions in human evolution, including the extinction of Australopithecus afarensis, the origin of the genus Homo, and the appearance of concentrated stone tool assemblages forming recognizable archaeological sites. The period also marks important changes in Earth's climatic history, with the onset of northern hemisphere glaciation starting sometime between 2.8-2.5 Ma and it remains an unresolved question in paleoanthropology whether or not the global climatic events influenced in whole or in part, local terrestrial paleoenvironments in Africa and, through this, the course of human evolution.
Changes in the terrestrial mammalian faunas of East Africa during this time interval are an important source of data about terrestrial paleoenvironments, and it has been argued that during this time period the mammalian faunas of Africa experienced a sudden pulse in the extinction and origination of taxa. The data corroborating this Turnover Pulse Hypothesis derive from both large-mammal and micromammal data, though the fossil record of the former is much more abundant in this interval. New micromammal fossils recovered from ca. 2.4 Ma deposits at locality A.L. 894, low in the Busidima Formation in the Hadar study area of the Afar region, Ethiopia, reveal a significant faunal turnover when compared with previously published material from older 3.2 Ma micromammal assemblages from the Hadar Formation deposits. The results support the hypothesis of a major faunal transition, but larger sample sizes and more extensive temporal sampling are needed to refine the time and rate of change within this interval at Hadar.

300万至200万年前（Ma）的时间区间，标志着人类演化历程中的若干关键转折：包括南方古猿阿法种（Australopithecus afarensis）的灭绝、人属（Homo）的起源，以及可辨识考古遗址所对应的集中型石器组合（stone tool assemblages）的出现。该时段同时对应地球气候史的重大变革——北半球冰期（northern hemisphere glaciation）于280万至250万年前启动。古人类学（paleoanthropology）领域至今仍存在尚未解决的核心议题：全球气候事件是否整体或部分影响了非洲本土的陆地古环境（terrestrial paleoenvironments），并由此作用于人类演化的进程。

此时间段内东非陆地哺乳动物群（mammalian faunas）的变化，是获取陆地古环境数据的重要来源。有学者提出，非洲哺乳动物群在此期间经历了类群（taxa）灭绝与起源的突发性更替脉冲。支撑该更替脉冲假说（Turnover Pulse Hypothesis）的数据来自大型哺乳动物与小型哺乳动物两类观测资料，不过此区间内大型哺乳动物的化石记录更为丰富。

科研人员从埃塞俄比亚阿法尔地区哈达研究区布西迪马组（Busidima Formation）下部、约240万年前的A.L. 894遗址沉积层中发掘的新型小型哺乳动物化石，与此前公开的哈达组（Hadar Formation）320万年前更古老地层中的小型哺乳动物组合（micromammal assemblages）资料对比后，展现出显著的动物群更替现象。本研究结果支持大型动物群发生重大更替的假说，但仍需更大样本量与更广泛的时间尺度采样，方能细化哈达地区此区间内演化更替的时间节点与变化速率。