This idea, dangerous as it was to the fabric of orthodoxy, and involving a profound separation from the general doctrine of the Church, seems to have been abroad among thinking men, for we find in the latter half of the same century even Linnaeus inclining to consider it.

It was time, indeed, that some new theological theory be evolved; the great Linnaeus himself, in spite of his famous declaration favouring the fixity of species, had dealt a death-blow to the old theory.

In his Systema Naturae, published in the middle of the eighteenth century, he had enumerated four thousand species of animals, and the difficulties involved in the naming of each of them by Adam and in bringing them together in the ark appeared to all thinking men more and more insurmountable.
What was more embarrassing, the number of distinct species went on increasing rapidly, indeed enormously, until, as an eminent zoological authority of our own time has declared, "for every one of the species enumerated by Linnaeus, more than fifty kinds are known to the naturalist of to-day, and the number of species still unknown doubtless far exceeds the list of those recorded." Already there were premonitions of the strain made upon Scripture by requiring a hundred and sixty distinct miraculous interventions of the Creator to produce the hundred and sixty species of land shells found in the little island of Madeira alone, and fourteen hundred distinct interventions to produce the actual number of distinct species of a single well-known shell.
Ever more and more difficult, too, became the question of the geographical distribution of animals.

As new explorations were made in various parts of the world, this danger to the theological view went on increasing.

The sloths in South America suggested painful questions: How could animals so sluggish have got away from the neighbourhood of Mount Ararat so completely and have travelled so far?
The explorations in Australia and neighbouring islands made matters still worse, for there was found in those regions a whole realm of animals differing widely from those of other parts of the earth.
The problem before the strict theologians became, for example, how to explain the fact that the kangaroo can have been in the ark and be now only found in Australia: his saltatory powers are indeed great, but how could he by any series of leaps have sprung across the intervening mountains, plains, and oceans to that remote continent?
and, if the theory were adopted that at some period a causeway extended across the vast chasm separating Australia from the nearest mainland, why did not lions, tigers, camels, and camelopards force or find their way across it?
The theological theory, therefore, had by the end of the eighteenth century gone to pieces.