Dean M C, Beynon A D, Thackeray J F, Macho G A
Department of Anatomy and Developmental Biology, University College London, United Kingdom.
Am J Phys Anthropol. 1993 Aug;91(4):401-19. doi: 10.1002/ajpa.1330910402.
There has been disagreement about whether the earliest hominids grew in a similar manner to great apes or modern humans. This has important biological implications, since it may have been inappropriate to apply modern human developmental standards to early hominids. The aim of the present study was to combine data from replicas of tooth surfaces, computed tomographic (CT) scans, and radiographs with data from a histological section of the canine crown, in order to provide a complete description of tooth crown and tooth root development in a single early hominid specimen (SK 63). Although partially destructive in nature, we have been able to determine the most reliable data yet for aspects of dental development in an important juvenile early hominid specimen. Appositional enamel formation time in the permanent right canine was estimated at between 305 and 418 days, imbricational enamel formation time at 819 days, and total crown formation time at between 3.18 and 3.48 years. The most likely age at death was estimated at around 4 years with a range of ages calculated between 3.18 and 4.23 years based on differences in timing of initial mineralization of the canine and differences in appositional enamel formation times. Crown formation times of the lower central and lateral incisors were estimated between 2.35-2.68 years and 2.57-2.91 years, respectively. Crown formation time of the first permanent molar was estimated at 2.4 years. Wear facets on the first permanent molars indicate that gingival emergence had occurred sometime prior to death, between 3 and 4 years of age. Estimates of root extension rates in the first permanent molars and in the permanent incisors are fast, and either within or above ranges of rates estimated for modern great apes. While we recognize that data for one individual may not be representative of data for a whole population of early hominids, the data for age at death, for age of M1 emergence, and for root extension rates presented here accord with those known for modern great apes and fall beyond the known ranges for modern humans.
关于最早的原始人类的生长方式是否与大猩猩或现代人类相似，一直存在分歧。这具有重要的生物学意义，因为将现代人类的发育标准应用于早期原始人类可能并不合适。本研究的目的是将牙齿表面复制品、计算机断层扫描（CT）和X光片的数据与犬齿冠组织切片的数据相结合，以便对一个早期原始人类标本（SK 63）的牙冠和牙根发育进行完整描述。尽管本质上具有一定的破坏性，但我们已经能够为一个重要的幼年早期原始人类标本的牙齿发育方面确定迄今最可靠的数据。右侧恒犬齿的釉质沉积形成时间估计在305至418天之间，叠瓦状釉质形成时间为819天，牙冠总形成时间在3.18至3.48年之间。最可能的死亡年龄估计约为4岁，根据犬齿初始矿化时间的差异和釉质沉积形成时间的差异，计算出的年龄范围在3.18至4.23岁之间。下颌中切牙和侧切牙的牙冠形成时间分别估计在2.35 - 2.68年和2.57 - 2.91年之间。第一恒磨牙的牙冠形成时间估计为2.4年。第一恒磨牙上的磨损面表明牙龈萌出在死亡前的某个时间发生，即在3至4岁之间。第一恒磨牙和恒切牙的牙根延伸速率估计很快，处于或高于现代大猩猩估计的速率范围。虽然我们认识到一个个体的数据可能不代表整个早期原始人类群体的数据，但这里给出的死亡年龄、M1萌出年龄和牙根延伸速率的数据与现代大猩猩已知的数据一致，且超出了现代人类已知的范围。
