Goes back way before towns.
When Europeans first showed up in the Caribbean, the native Arawaks were in the process of being replaced by Carib tribes from S. America.
The Caribs had a regular procedure for warfare. They would attack an island, kill (and eat) all the men and children, impregnate the women and then leave. They'd come back five to seven years later, take the children with them be raised as members of the Carib tribe, impregnate the women again. Rinse and repeat.
The Arawaks would probably have lasted only another century or two. But of course European diseases and exploitation wiped them out in a couple of decades instead.
The New Zealand Maori got some European ships to take them to the Chatham Islands, where related but long separated peoples called the Moriori lived. These are perhaps the only example on record of a totally pacifist society.
The Maori promptly demonstrated why. They marched in, killed (and ate) whatever men they chose to, and raped and enslaved all the women. Pretty well exterminated the Moriori in less than 30 years.
http://en.wikipedia.org/wiki/Moriori_people
Thanks, that could make a nice topic (or two)!