1981 Volume 23 Issue 1 Pages 141-146
Mammalian bone remains composed of 22 species belonging to 6 orders, were found at the rockshelter site in Tochibara, Kita-Aiki-Mura, Minami-Saku-Gun, Nagano Prefecture (This site is said to be from the earliest stage of the Jomon Period, or about 8, 400 years B. P.). Among the small mammals, Apodemus speciosus was a relatively abundant species.
This article deals with the size differences of the lower molars between the earliest Jomon Period and the living specimens of Apodemus speciosus. The region from which the living materials were collected was Mt. Yatsugatake, adjacent the Tochibara Site.
The two parameters measured were the mesio-distal crown diameter and the bucco-lingual crown diameter of each molar.
Mesio-distal crown diameter (md), bucco-lingual crown diameter (bl) and rectangle (md×bl) were generally larger in the Jomon Period pecimens than the living one. The size difference was the smallest in the first molar, and was the largest in the third molar. The reduction tendency of the third molar against to the first molar was conspicuous in the living specimens.
It was estimated that the size difference of the molars between the Jomon Period and the living specimens was the result of the climatic change that occured during this period. It has been suggested that the annual mean temperature of the earliest Jomon Period was 2 to 3°C below that of recent years.
