This candidate seems worthy of the name Cerebral Code . Parcellation, as when rising sea level converts the hilltops of one large island into an archipelago, typically speeds evolution. When rising sea level converted part of the coastline of France into the island of Jersey, the red deer trapped there in the last interglaciation underwent a considerable dwarfing in only a few thousand years. When subsequent pioneers rediscover the unused resources, their descendants go through a series of generations where there is enough food even for the more extreme variations that arise, ones that would ordinarily lose out in the competition with the more optimally endowed. When the environment again changes, some of those more extreme variants may be able to cope better with the third environment than the narrower range of variants that would reach reproductive age under the regime of a long-occupied niche.
Archipelagos allow for many parallel experiments.
Most evolutionary change may occur in such isolation, in remote valleys or offshore islands, with major continental populations serving as slowly changing reservoirs that provide pioneers to the chancy periphery. When a territory's excitability falls below the requirements for maintaining triangular arrays, it becomes a barrier. Error correction can be escaped at narrow gateways through such barriers, allowing variants to arise that compete with the parental patterns. And thanks for all the feedback so far via the 1992-95 posters.