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.

The dogu are oddly hypnotic, a parade of the beautiful, brutal and uncanny: a cat-faced dogu, designed without legs; a dogu with an outsize heart-shaped face; a sturdy dogu wearing an enigmatic triangular mask, and perhaps most famous of all, a “goggle-eyed” dogu from Kamegaoka covered in stippled and corded markings.

There are dogu with horns, with flat heads, bow-legs, dogu wearing bodices, knee-pads, dogu holding pots. Some dogu invite immediate empathy, like the fragmentary figure of a mother cradling a baby; others, like the lofty standing dogu, nearly half a meter tall, appear hieratic and inscrutable. It seems hard to believe they could all represent a common phenomenon, one to which Meiji Era archaeologists in 1882 first gave the name “dogu.”

“The rich diversity of the dogu tradition is one of the themes we wanted to present in the exhibition,” explains curator Dr. Simon Kaner, an archaeologist of the Sainsbury Institute who specializes in the prehistory of Japan. “The Japanese archipelago during the Jomon period was occupied by a large number of different groups of people, or different societies — we should talk not of Jomon culture but Jomon cultures, Jomon peoples and not Jomon people. They probably spoke a number of different dialects and expressed themselves through a huge range of pottery styles — over 400 local styles have been recognized to date.”

Indeed, the dogu are both an intensely local form of expression, and also manifest a shared urge by Neolithic peoples around the world to represent the human form in clay. Humanoid figures of a comparable age have been found as far afield as Mexico, Turkey, Ecuador, Romania and Egypt. Curiously, Japan’s nearest neighbors do not appear to have had an equivalent tradition.

“There are very few ceramic figures from the Korean Peninsula,” says Kaner. “And in China the human form was represented by painting on pots, or by very different forms, like the ‘temple’ or ‘shrine’ from Niuheliang, which has life-size unbaked clay figures around the walls.”

So what did the dogu mean to their Jomon makers? The British Museum exhibition is part of an ongoing debate in the field of Neolithic studies as to the nature and purpose of early sculptural representation of the human form.

The 1960s saw a proliferation of theories around so-called “mother goddess” figures, often nicknamed “Venus.” (Indeed, pride of place in the current exhibition goes to a big-bottomed dogu known as the Tanabatake “Venus” — a label Kaner agrees is “not very helpful.”) The “Venus” theory has declined in popularity in recent years, while scientists working on a hoard of 2,000 figures found at Catalhoyuk in Turkey announced earlier this month a new hypothesis that the artifacts were not ritual objects, but simply toys.

The function of dogu remains mysterious. Many were, like the Catalhoyuk figurines, “everyday” objects — the majority have been found broken, some in heaps. If they were toys, what does that imply about the status of children, or the very idea of childhood, in Jomon cultures? Some dogu were, certainly, given special treatment — placed alongside burials or “enshrined” in pits. Kaner thinks “there is scope for both ‘everyday’ figures and objects of veneration within the dogu tradition.”

Whatever their ritual or workaday function, the dogu are also, irresistibly, art. Their whimsical forms enchant, and their craftsmanship — some dogu are large and hollow, many are perfectly balanced and freestanding — is undoubted. An essay in the handsome catalog makes a case for the dogu as art, and for the current exhibition as a “turning point” in the wider recognition of that artistry. Their first champion in this regard, however, was the avant-garde artist Taro Okamoto, whose “The Myth of Tomorrow” was unveiled in Shibuya Station last year.

Okamoto’s work, both painting and sculpture, was profoundly influenced by his affinity with Jomon design. He wrote of one encounter with a piece of Jomon pottery: “My blood boiled to a tremendous heat and then burst into flames.” On another occasion, he reflected: “The violent existence of Jomon ceramics manifests itself in a pulse of energy that can never be grasped by normal aesthetics and intellectual control.”

Another Jomon enthusiast was Nobel prize-winning author Yasunari Kawabata, who had a dogu on his desk. It is a lugubrious figure with a heart-shaped face, and Kawabata described in an essay how “it is sitting here in front of my writing paper and speaking to me.”

Dogu still speak — albeit through rather different media today. They feature in the “Understanding Japanese History” comic-book series narrated by cult robocat Doraemon, whose human sidekick Nobita remarks that they “look like aliens.” In the PlayStation game “Dokioki,” the dogu are indeed aliens. Shinji Nishikawa’s “Dogu Famir,” a seven-volume comic series, features a family of figurines trying to fit into everyday life — shopping, attending school and protecting the usual assortment of scantily-clad manga heroines from an evil, UFO-controlled dogu.

In the British Museum’s beautifully presented exhibition space, it is a pleasure to pull up a folding seat and sit in front of a dogu. They have so much to say.

“The Power of Dogu: Ceramic Figures from Ancient Japan” is running at the British Museum, London, Room 91, till Nov. 22; admission is free. The show moves to the Tokyo National Museum, Room T5 Honkanon, from Dec. 15 to Feb. 21, 2010.