Analysis of a microcephalic child from the late period (ca. 1100-1700 A.D.) of central California.

Microcephaly is a severe developmental abnormality which is induced either genetically or environmentally. The archaeological evidence for the occurrence of this abnormality is minimal. Out of six possible cases, only three have been published; all are adult and represented solely by cranial remains. The focus of the current study is the nearly complete skeleton of a 3-year-old child recovered during archaeological excavations in San Jose, California. The individual is compared to a sample of 184 California Indians, ranging from 0.5 to 5 years, which were also recovered from archaeological excavations. In order to determine if microcephaly was the only disorder represented, metrical comparisons of the skull and postcrania and gross morphological comparisons of endocranial casts were made. Based on these comparisons the individual was determined to have a cranial vault size comparable to 6-month-old infants (630 cc), a facial skeleton equivalent to the 9-month-old to 2-year-old age groups, and a reduced stature. Due to the mosaic nature of the skull, the observed morphology was interpreted in terms of functional cranial components. Severe malformation of the orbital aspect of the frontal lobes was found in conjunction with a significant reduction in size of the cerebral cortex and left temporal lobe. On the basis of this analysis, the individual was found to exhibit the total morphological pattern associated with microcephaly. A differential diagnosis of other possible genetic disorders is also presented.