The enlarged Southeast Asian continental area which was created when sea levels dropped in periods of glaciation. Much of western Indonesia was then connected to the mainland. Until about 7000 BC, the seas were some 150 feet (50 m) lower than they are now, and the area west of Makassar Strait consisted of a web of watered plains that is called Sundaland. These land connections may account for similarities in early human development observed in the Hoabinhian age, which lasted from about 13,000-5000/4000 BC. The stone tools across Southeast Asia during this period show a remarkable degree of similarity in design and development.