A health crisis during the Japanese Medieval Period: A new paleodemographic perspective.

Objective: To test the hypothesis that the "Little Ice Age" (LIA) (in Japan, ˜1440 - 1730 CE) co-occurred with unique age-at-death patterns.

Materials: 810 adult human skeletons from the early Medieval Period (EMP) of Japan, which are contemporaneous with the Medieval Warm Period (10th - mid 13th century AD), and the late Medieval Period (LMP) and Edo Period, which are contemporary with the LIA.

Methods: Age at death and sex was determined for each skeleton and demographic profiles of the Yayoi Period (5th century BC - 3rd century AD), EMP, LMP, and Edo site samples were compared. Paleopathological data from previously published reports were evaluated.

Results: The EMP had the highest mortality among young adults. Longevity increased in the samples (LMP and Edo) contemporaneous with the LIA.

Conclusions: EMP early age-at-death was the result of poor community health, violent death, and frequent large-scale natural catastrophes. The LMP and Edo Period samples have an older age-at-death pattern and higher frequency of stress markers, argued to be a consequence of a colder climate.

Significance: This study is the first to synthesize paleodemographic and paleopathological data on a large scale to assess the possible effects of the Little Ice Age in Japan.

Limitations: Varying skeletal preservation and focus on adult skeletons reduces the ability to evaluate health throughout the life span.

Suggestions For Further Research: Analysis of nonadult remains and multiple health indicators will likely shed more light on the effects of the Little Ice Age in Japan.