Thousands of years ago，human(人类)didn’t live in towns．Sometimes they would live in caves(洞穴)or build camps in the forest．Only about thirty people1 in each camp．The men would go hunting while the woman and children2food from trees around the camp．All the food was 3 among people in the group．Every few weeks they moved to another place to find more food．It was a simple life，but people had to be 4 .They had to make everything that they needed，and they had to know a lot about plants and animals．Nowadays most people live in towns and cities，and they work in offices and