H. Beam Piper's Little Fuzzy series. Four total books. Little Fuzzy, Fuzzy Sapiens, Fuzzies and Other People, Fuzzy Bones (with William Tuning). Published around 1975.
Henry Beam Piper (1904 - 1964) was an American science fiction author. He wrote many short stories and several novels. He is best known for his extensive Terro-Human Future History series of stories and a shorter series of "Paratime" alternate history tales.