Geological evidence indicates that much of what is now Bangladesh was formed 1 – 6.5 million years ago during the Tertiary Era.
Implements discovered in the village of Deolpota in the neighboring state of West Bengal suggest that a paleolithic civilization existed in the region about 100,000 years ago. The evidence of a paleolithic civilization in East Bengal or Bangladesh region is limited to a stone implement in Rangamati and a hand axe in the hilly tip of Feni district, whose ages are thought to be 10,000-15,000 years old.
The New Stone Age in the region lasted from 3,000 B.C. – 1,500 B.C. Neolithic tools have been found at Sitakunda in Chittagong. Hand axes and chisels, which show a close approximation to neolithic industries in West Bengal, Bihar and Orissa have been discovered at Mainamati near Comilla. Thinly-forested laterite hills in East Bengal, which was dotted with fertile valleys provided a favorable environment for neolithic settlements.