hill stations, forts, and three World Heritage Sites, Tamil Nadu's tourism industry is the largest among the Indian states. 15% of Tamil Nadu's forests are protected areas, as its hosts diverse wildlife. The Tamil film industry, nicknamed as Kollywood, plays an influential role in the state's popular culture. History Prehistory Archaeological evidence points to this area being one of the longest continuous habitations in the Indian peninsula. In Attirampakkam near Chennai, archaeologists from the Sharma Centre for Heritage Education excavated ancient stone tools which suggest that a hominid population existed in the Tamil Nadu region somewhere around 1,000 years before homo sapiens arrived from Africa. A Neolithic stone celt (a hand-held axe) with the Indus script on it was discovered at Sembian-Kandiyur near Mayiladuthurai in Tamil Nadu. According to epigraphist Iravatham Mahadevan, this was the first datable artefact bearing the Indus script to be found in Tamil Nadu. According to Mahadevan, the find was evidence of the use of the Harappan language, and therefore that the "Neolithic people of the Tamil country spoke a Harappan language". The date of the celt was estimated at between 1500 BCE and 2000 BCE. In Adichanallur, from Tirunelveli, archaeologists from the Archaeological Survey of India (ASI) unearthed 169 clay urns containing human skulls, skeletons, bones, husks, grains of rice, charred rice, and celts of the Neolithic period, 3,800 years ago. The ASI archaeologists have proposed that the script used at that site, Tamil Brahmi, is "very rudimentary" and date it somewhere between the 5th century BCE and 3rd century BCE. About 60 per cent of the total epigraphical inscriptions found by the ASI in India are from Tamil Nadu, and most of these are in the Tamil language. In Keezhadi near Madurai, excavations have revealed a large urban settlement dating to the 6th century BCE, during the time of urbanisation in the Gangetic plain. During this dig, some potsherds were uncovered with a script similar to Indus script, leading some to conclude it was a transition between the Indus Valley script and Tamil Brahmi script used in the Sangam period. Sangam period (500 BCE–300 CE) The early history of the people and rulers of Tamil Nadu is a topic in Tamil literary sources known as Sangam literature. Numismatic, archaeological and literary sources corroborate that the Sangam period lasted for about eight centuries, from 500 BCE to 300 CE. The recent excavations in Alagankulam archaeological