At the Iyai Rockshelter Site in Gunma Prefecture, a large number of obsidian stones have been excavated from Initial Jomon layers and burial pits. As a result of obsidian provenance analysis by X-ray fluorescence, they were found to have been brought in from the obsidian source around Wada Pass (Kobukazawa and Hoshigato) in Nagano Prefecture. In addition, it was found that the form and source of origin of obsidian arrowheads (hoe-shaped arrowhead and Yanagikubo type) differed depending on the stratigraphy.

When we examined the morphology, source, and distribution trend of lithic arrowheads from the same period in the Gunma region, we found that there was an active area in the middle basin of the Tone River and return migration originated from this base in the hoe-shaped arrow stage (Oshigatamon stage). However, it was found that a base that of activity was formed at the southern foot of Mt. Akagi in the Yanagikubo-type stage (Chinsenmon stage). It was also found that the movement of people and information to and from the eastern Kanto region also differed depending on the time period. In both periods, the procurement of obsidian based on an embedded strategy was adopted.

This paper outlines the research results obtained from the excavation and analysis of excavated materials at the Iyai rock shelter site, Gunma Prefecture, and discusses their scientific significance. The excavation of buried human remains of more than 40 individuals is particularly important because it allows us to understand the morphological characteristics, inter-individual variation, genetic phylogeny, and health status in the Initial Jomon period at the population level. The excavated human remains include many matrilineal relatives with identical mitochondrial genome haplotypes, which may allow us to empirically reconstruct family, marital, and group structures. New findings on funerary systems have also been obtained, including the discovery of a unique burial method in which mummified bodies are cut off at the waist. Furthermore, we have obtained various data to reconstruct the ecology and behavior of the Initial Jomon people in mountainous areas, such as the use of plant and animal resources, the seasonality of animal hunting, the actual state of bone and antler production and leather use, and the area of activity and residential patterns.

The Iyai rockshelter site in Naganohara town, Gunma Prefecture, Japan, is an extremely important archaeological site in terms of human activity from the Initial to Early Jomon Period. In addition to 75 radiocarbon ages derived mainly from charcoals, results of dating 66 samples from human bone and other carbonized materials attached to Jomon pottery were summarized to clarify the temporal transition of human activities at the Iyai rockshelter site. The thick ash layer that has deposited on the terrace in front of the rock shelter area was dated back to 10,000 cal BP, in the middle Initial Jomon period, and indicates the oldest and most prominent evidence of human activity in this site. The earliest skeletal remains in Layer II at the in the rockshelter was dated to the Early Late Jomon Period (8,600-8,000 cal BP). The skeletal remains of layer I-II in the the rock shelter area is 6,900-5,900 cal BP. These dates indicate that the Iyai rockshelter site has been used repeatedly for approximately 4,000 years.