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17.4: Differences Between Adult and Subadult Skeletons

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    The adult skeleton consists of 206 bones. Each of these bones develops from a number of centers of ossification. It is estimated, then, that a baby is born with approximately 450 bones that grow from their centers of ossification and eventually become the 206 bones of the adult skeleton. For example, a typical long bone (e.g., tibia) has three centers of ossification: one primary center, the diaphysis; and two secondary centers, the epiphyses. In between epiphysis and diaphysis is an epiphyseal growth plate of cartilage that will remain unfused until postnatal growth is complete after puberty (and for some bones, well into adulthood). There is a relatively well documented order in which bones of the subadult postcranial skeleton reach full fusion, which is used as the basis for age estimation in forensic contexts (Bass 2005; White and Folkens 2000).

    Similarly, the sutures between cranial bones in children are unfused, which allows skull growth to coincide with brain growth and provides a basis for age estimation based on suture fusion. The skulls of babies are marked by several fontanelles (soft spots), which are areas of the skull filled with membrane that has not been replaced with bone through intramembranous ossification.

    Finally, the age of the subadult skeleton can be estimated based on teeth. All mammals develop two sets of teeth: deciduous (baby) teeth and permanent (adult) teeth; humans are no exception. Permanent human teeth were described immediately above. It is worth spending a few words to describe deciduous human teeth. At birth, humans usually display no teeth, but by about six months of age, the deciduous lower central incisors usually appear (see Bass 2005). When the complete sequence of deciduous teeth has erupted, there are five teeth in each quadrant: two incisors, one canine, and two molars. Deciduous incisors and canines are eventually replaced by their adult counterparts; deciduous molars are replaced by adult premolars, and there is no deciduous precursor to adult molars. The eruption patterns of deciduous and adult teeth is well documented and is used as in forensic contexts to estimate age (Bass 2005).

    This page titled 17.4: Differences Between Adult and Subadult Skeletons is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Beth Shook, Katie Nelson, Kelsie Aguilera, & Lara Braff, Eds. (Society for Anthropology in Community Colleges) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.