LONDON — They are, according to their kanji, part earth and part spirit, somewhere between animal and human. They are dogu, the most remarkable products of Japan's Jomon Period, a Neolithic era before the advent of rice cultivation, when the Japanese archipelago supported higher population densities than any other pre-agricultural society in the world.

The dogu are humanoid forms shaped in clay, large and small, richly decorated or homely and unadorned. Some 18,000 of them have been unearthed to date, in Jomon-period settlements stretching from Kyushu, north through Tohoku to Hokkaido. The oldest are nearly 10,000 years old, the youngest a mere 2,300. Yet despite their advanced age, they're on the move.

Sixty-seven dogu, loaned from collections across Japan, have taken up temporary residence in the British Museum, London, for a new exhibition: "The Power of Dogu." In December, they return home for three months' display at Tokyo National Museum.