Before the arrival of Europeans, the indigenous peoples of the Americas were diverse and varied in physical appearance. North American indigenous peoples had a range of skin colors from light to dark. Central and South American indigenous peoples had hair that ranged from straight to curly, and skin tones also varied. Many indigenous people had strong and muscular builds and were adapted to their environments. The demographic features of the indigenous peoples of the Americas were characterized by distinct cultural and linguistic groups, with an estimated population of 40 to 100 million people. They had developed their own social, political, and economic systems that were influenced by their environment and cultural practices.