The land that is now Pakistan formed hundreds of millions of years ago.
Thousands of millions of years ago, geologists believe that there existed a supercontinent, Pangaea. This continent broke into half. The northern half contained North America, Europe and some parts of Asia and the southern part, known as Gondwanaland, contained the Indian subcontinent. About 200 million years ago Gondwanaland began breaking apart into the current continents. Evidence for this theory comes from the discovery of whale bones found near Peshawar indicating that the northern part of our subcontinent was once under water.
One of the largest land mammals known to have lived was discovered in Dera Bugti, Balochistan. Baluchitherium, a rhinoceros, lived during the Oligocene epoch, about 30 million years ago. It stood at over 5 meters, was 7 meters long and weighed about 20 tons. And unlike the modern rhinos it did not have a horn.
Over 20,000 fossils have been discovered in Dera Bugti alone. This and discovery of other fossils has lent credit to the hypothesis that pehistoric Balochistan was the place of migration of mammals from Southeast Asia to Africa or Europe.
Hussain, Jain. An Illustrated History of Pakistan (Book 1). Karachi: Oxford UP, 1981.