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

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

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.

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.

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

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.

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.

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

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