There weren't large numbers of attackers back then. The article is talking about the Neolithic-Era so approx 3500 BC. I would say that it would be relatively ea

There weren't large numbers of attackers back then. The article is talking about the Neolithic-Era so approx 3500 BC. I would say that it would be relatively easy to defend against 5x the amount of people if you could pick them off as they swam across the water. You literally could be throwing spears or rocks at them as they tried to swim.