This linguistic hyperdiversity resulted from a number of factors: continuing waves of migration, the existence of numerous decentralised and generally self-sufficient communities, hostilities between people groups, with none able to dominate any of the others, and the difficult geography of Vanuatu that impeded inter- and intra-island travel and communication. The geological record also shows that a huge volcanic eruption occurred on Ambrym in circa 200 AD and on Kuwae in c. 1452–53 AD, which would have devastated local populations and likely resulted in further population movements.