The people of ancient Greece saw the arrival of the human settlers during the Paleolithic era (200,000–3300 BC) more than 200,000 years ago. They were tribes that survived by hunting and gathering in the wild environment of Greece. They sought shelter in caves while hunting animals and gathering fruits, nuts and plants for sustenance. Archaeological findings indicate that one skull has been dated more than 200 thousand years ago and the other two, from 200 thousand to 150 thousand years ago. These discoveries mark the presence of Homo sapiens in Eurasia. As civilization advanced into the Neolithic era around 7 millennia before Christ farming societies started to take shape. During this era or period of history, individuals began to grow crops like wheat and barley and tame animals as pets, maritime trade was introduced which signified a shift in how they lived their lives. The two earliest unreadable writings from that time frame are estimated to be from around 5,300 to 4,500 B.C.