In 1877, the Harvard-trained biologist Edward Sylvester Morse, freshly arrived in Japan, took the new train from Tokyo to Yokohama. As he passed through Omori he looked out the window and saw a long, high mound. From having dug into many a similar mound back home in Massachusetts, he knew exactly what he was looking at: a prehistoric shell midden, a great trash heap built up by many generations of clam-diggers. A few months later he returned with a party of students and began the first modern archaeological dig in Japan.

Morse, then a professor at the University of Tokyo, is considered the father of biology, zoology and archaeology in Japan. He discovered in the midden a lost culture, unknown to the modern Japanese. Apart from seashells and fishbones, the mound yielded animal bones, stone and bone tools, fragments of wood and wicker, and, especially, lots and lots of potsherds.

The orange-red earthenware was subsequently found at hundreds of other sites all over Japan, in strata ranging from around 300 B.C. to over 10,000 B.C., making it the oldest known pottery in the world. (The oldest known Near Eastern pottery, by contrast, dates only to the seventh millennium B.C.) The elaborate impressed-cord marking on the vessels provided the name by which both the style and the culture are known: Jomon, "cord-mark."