Analysis of information sources in references of the Wikipedia article "Pā" in English language version.
The period of the fourteenth and fifteenth centuries has been termed transitional [...]. [...] the practice that developed of preserving kumara tubers in storage pits (a process that had been unnecessary in a tropical climate) meant that communities had to remain with those pits, particularly in an era of larger population when competition for resources meant that less well-provisioned neighbours might be tempted to raid your larder. This last factor more than any other gave impetus to the rise and spread, from north to south, of fortified hilltops which came to be known as pa. They probably originated from a need to protect kumara tubers; but they persisted and became more important when population growth, competition for all resources, the pursuit of mana or authority for one's own group, and a generally more martial culture meant that communities increasingly had to protect themselves from immediate neighbours or from marauding enemies from further afield.
