Morphoogical study of the dietary adaptation of Miocene hominoids

自上世纪80年代以来，日本研究人员在肯尼亚北部图尔卡纳湖以南100公里处的Nachola和Samburu Hills地区发现了许多中新世古人类的牙齿化石。本项目的目的是通过对牙齿化石的形态分析来估计这些中新世古人类的饮食适应性。研究策略有几个步骤。首先，我们通过收集和整理先前发表的参考文献，定量分析了现存灵长类动物的饮食适应性。其次，我们利用新引入的三维数字化测量系统，对这些灵长类动物牙齿的外部形态进行了精确的记录。第三，我们综合了饮食菜单和牙齿形态特征的数据。第四，将获得的相关性应用于中新世古人类和其他古人类化石的牙齿形态解释。除了现存灵长类动物饮食专业化的旧档案外，今年我们还收集了特别强调非洲和亚洲猿类的新数据。此外，我们还测量了现存灵长类动物的添加剂新材料，包括黑猩猩、倭黑猩猩、大猩猩、猩猩、长臂猿、狒狒、红疣猴、日本猕猴、cebids。灵长类化石材料有来自中中新世东非的Kenyapithecus和Nyanzapithecus，来自早中新世东非的Proconsul spus，来自Laetoli的Australopithecus afarensis和其他上新世人科动物。澄清的主要结果如下。首先，东非早中新世的古人类，如Proconsul，具有高冠尖的特征，这表明他们的饮食偏好具有中等韧性纤维的食物。第二，中新世中期的肯尼亚猿人，相比之下，有圆形和低尖，表明更依赖于坚硬的坚果和树皮。第三，自拟古猿表现出更适合磨牙的牙齿形态，这表明它们的饮食菜单更独立于坚硬的食物，如坚硬的坚果、谷物和树皮。

From the Nachola and Samburu Hills regions, 100 km south of Lake Turkana, northern Kenya, many fossil teeth of Miocene hominoids were discovered by Japanese researchers since 80ls. The aim of this project is to estimate dietary adaptations of these Miocene hominoids by morphological analyzes of the fossils teeth.The research strategy has several steps. First, we analyzed dietary adaptations among living primates quantitatively by collecting and sorting previously published references. Second, we recorded precise external morphology of these primates teeth by using the newly introduced three dimensional digitizing and measuring system. Third, we synthesized the data about dietary menu and morphological features of tooth. Fourth, we applied obtained correlations to the interpretation of the tooth morphologies of the Miocene hominoids and other fossil hominoids/hominids. In addition to an old archive of the dietary specialization of living primates, this year we collected new data especially emphasizing African and Asian apes. Also, we measured additive new materials of living primates, which include chimpanzees, bonobo (=pygmy chimpanzee), gorilla, orangutan, gibbons, baboons, red colobus, Japanese macaque, cebids. Materials of fossil primates are Kenyapithecus and Nyanzapithecus from Middle Miocene East Africa, Proconsul spp. from Early Miocene East Africa, Australopithecus afarensis from Laetoli and other PlioPleistocene hominids.Major results clarified are as follows. First, East African early Miocene hominoids such as Proconsul characteristically displays high crown cusps, suggesting a dietary preference on food stuff with moderately tough fibers. Second, Middle Miocene Kenyapithecus, in contrast, has round and low cusps, suggesting more dependence on hard nuts and barks. Third, austolaropithecines exhibit more grinding adapted dental morphologies, suggesting a dietary menu with a more independence on hard an tough stuff such as hard nuts, grains and barks.