Buttons made from seashell were used in the Indus Valley Civilization for ornamental purposes by 2000 BCE. Some buttons were carved into geometric shapes and had holes pierced into them so that they could be attached to clothing with thread. Ian McNeil (1990) holds that: "The button, in fact, was originally used more as an ornament than as a fastening, the earliest known being found at Mohenjo-daro in the Indus Valley. It is made of a curved shell and about 5000 years old."
Functional buttons with buttonholes for fastening or closing clothes appeared first in Germany in the 13th century. They soon became widespread with the rise of snug-fitting garments in 13th- and 14th-century Europe. (Wikipedia)