The immutability of species

The idea that each individual species on the planet was specially created by God and could never fundamentally change. The idea that species were immutable by many pre-Darwin biologists. Species immutability is also a common claim among creationists but today some of the largest Young Earth Creationist groups agree that speciation can and does occur to some extent [1]. This limited speciation resolves the practical difficulty of fitting two of every species of animal on the ark - a quite impossible task - by instead allowing for only a much smaller number of species to be preserved, which would then diverge into the diversity seen today.