Between 33 percent and 50 percent of the species of the North Island might have vanished in the long interval between the arrival of people on Aotearoa and canoes a disconcerting memory of the fact that extinction here did not start with canoes but with climatic shocks and ash clouds.
A tight archive of the Early Pleistocene, including the fossils of 12 bird species and four frog species, was discovered in a cave near Waitomo by researchers working through fine sediments and most of the deposits are almost never preserved in that way by the surface landscapes of New Zealand. The setting matters. Caves can serve as time capsules, insulating delicate bones against weathering and erosion, and here the deposit will have a geological date, one with which biology can identify itself with definite moments of disturbance.
The remains were stuck in two separate layers of ash-fall between great eruptions one around 1.55 million years ago and the other around 1 million years ago a fact which allowed the scientists to date the fauna with uncustomary precision. That bracketing is not merely a fulfilment of curiosity; it offers that type of baseline which makes subsequent change measurable. Paul Scofield summed up the magnitude of the gap filled by this: It is not a lost chapter in the antique history of New Zealand, but a lost volume.
What the team has meant by the expanded assertion is that human beings were not the issue but the ecological cast list of the island was already being redefined. The reframing was summed up by Trevor Worthy in a line which has become the pivot of the study: This is a recently identified avifauna of New Zealand, the one that was superseded by that humans stumbled on a million years ago. The fossils indicate a significant turnover long before the Late Pleistocene record that is generally the dominant feature of reconstructions of pre-human New Zealand.
The most striking bone is that of a parrot: Strigops insulaborealis, a very ancient ancestor of the kakaapo of the present day. The kaka-papo of the modern time is reputed to be heavy and to be unable to fly; the kaka-papo of the olden days seems to be constructed differently. The legs of the dead animals were found weaker in comparison with the living species a morphological fact which could be attributed to an animal that was less dependent on climbing, and possibly more on flight, but the authors are keen to point out that it is still not confirmed whether it could fly.
The portrait is extended by other fragments. The cave produced an extinct relative of the modern takahē, and an extinct relative of a pigeon that was very closely similar to Australian bronzewing pigeons. The blend with the frog remains suggests a forested world that did not just evolve into the current one, but was battered and disrupted again and again as climate swings at both ends and volcanic eruptions at intervals buried sterilizing films of ash over much of the North Island.
Those processes are consistent with the ecological argument of the study namely that sudden environmental resets can promote replacement just as effectively as new predators. The changing forest and shrubland ecologies required a re-setting of the bird fauna, Scofield said, and that can wipe out the specialists and favour the generalists, or the newcomers.
Simultaneously, genetics is starting to bring another dimension of resolution to that deep-time image. Independent studies of takahé have been conducted on sequenced ancient DNA to determine bottlenecks of population loss of diversity, demonstrating how climate oscillation and subsequent anthropogenic stresses produced varying traces in the lineage. In proximity to the Waitomo fossils, the message is both practical and historical conservation planning is advantageous when natural baselines are not supposed to be stable, singular, and recent.
The Waitomo cave does not simply put species on a list. It reinstates a lost gap – one in which the wildlife of New Zealand was already being influenced by forces large enough to bend forests, to divert rivers of ash, and to make quiescent decisions as to which birds would be available to meet man long after the time described.
