Life in jungle caves was very difficult for early humans as they regularly required to go far off river bank for drinking water. As water is the essential element for human life so, he decided living near river bank. Now they could get water easily and could use it for their various activities. They also knew that all animals come to river banks for drinking water, where they could be hunted easily.
The fishes in river was their best food, they could clean their living areas with water and could bath daily. Thus, the life of early humans became settled up to some extent now. Earlier they used to live in far off caves and it was very difficult to meet each other but now they started living in groups near river banks to help others and protect their family from wild animals, together.