The date at which New Zealand became separated from any large land mass is very vague, but certainly it was in very early times as shown by the large number of endemic species. The flowering plants which show affinities with plants of the Malayan region, such as kauri, Aciphylla, and Carmichaelia, are quoted in support of theories of ancient land connections. It is impossible to reconstruct the nature and extent of this ancient vegetation, though much research has recently been done in Paleobotany. But it is evident that vegetative changes took place as ice ages came and went, and climatic conditions changed. By the time the Maoris began to occupy the country, they found vast areas clothed in dense forest. In the centre of the North Island, however, volcanic eruptions had caused widespread destruction of the forests, the charred remains of which may now be found beneath showers of pumice and ash. Again, Maori occupation, especially in the use of fire for clearing areas for cultivation and for hollowing out their canoes, resulted in further forest losses. It was inevitable that European settlement, accompanied by the introduction of mammals, had far-reaching effects upon the vegetative cover. The indigenous vegetation had developed without the presence of land mammals (except two species of bat), but in recent years many of those introduced by man have been responsible for a great deal of damage to the vegetative cover. Many of these animals such as deer, goats, opossums, and the like not only eat leaves and destroy undergrowth, they trample young plants and so prevent the natural regeneration of forests, but they also make possible the onset of soil erosion and the general destruction of landscape features on a large scale.