TOKYO (AP) _ Motoo Kimura, a Japanese geneticist who caused an international stir by challenging Darwin's theory of evolution, has died at 70.

Kimura died of a cerebral hemorrhage Sunday, his 70th birthday.

His most influential work was in the areas of population genetics and evolution at the molecular level. In his 1968 ''Neutral Theory of Genetic Evolution,'' Kimura said the evolution of genes had little to do with Darwin's theory of natural selection, which called for the most fit to survive, and more to do with random mutations.

During his 41-year career, Kimura received numerous scientific awards in Japan and abroad. He received the Order of Culture, Japan's top prize for contributions to society, in 1976.

He was elected an honorary member of the American Academy of Arts and Sciences in 1978 and became a member of the Japan Academy in 1982.

Born Nov. 13, 1924, in Aichi prefecture, central Japan, Kimura was educated at Kyoto University and at the University of Wisconsin.

He is survived by his wife, Hiroko, and a son.