Oh well, I'm in disagreement with both of you....sigh...
As South Australian astronomer George Dodwell showed so clearly (the book on his material is overdue due to publisher problems), the earth has experienced more than one axis tilt. This has a lot to do with forests near the poles! Some of the easy to see evidence regarding this tilt: the earth is the ONLY planet with a moon not circling at the equator! The Temple of Karnak in Egypt originally had its main corridor in line with the summer solstice, as I recall. It no longer is. There are a number of monuments from ancient Egypt which are, according to the hieroglyphs, supposed to be at particular astronomical angles -- and all of them are off by the same amount.
However continental drift also helps with the explanation. But, first of all, the animals migrated before the separation of continents and, secondly, the separation was not slow, geologically speaking. It was catastrophic, and probably set off by an asteroid hit -- possibly where Iceland is now. If you look at a topographical map, you will see Iceland sitting smack on the Atlantic Rift. Is its volcanic heritage the result of a catastrophic instrusion into the crust of earth? We don't know, but it is certainly a viable theory.
The continental drift would be impossible without something under the earth's crust called the aesthenosphere.
The crust is thin, varying from a few tens of kilometers thick beneath the continents to to less than 10 km thick beneath the many of the oceans. The crust and upper mantle together constitute the lithosphere, which is typically 50-100 km thick and is broken into large plates (not illustrated). These plates sit on the aesthenosphere.
The aesthenosphere is kept plastic (deformable) largely through heat generated by radioactive decay. The material that is decaying is primarily radioactive isotopes of light elements like aluminum and magnesium. This heat source is small on an absolute scale (the corresponding heat flow at the surface out of the Earth is only about 1/6000 of the Solar energy falling on the surface). Nevertheless, because of the insulating properties of the Earth's rocks this is sufficient to keep the aesthenosphere plastic in consistency.
from http://csep10.phys.utk.edu/astr161/lect ... onics.html
The aesthenosphere is only 'plastic' now, but when there was a combination of the short and long half life elements all decaying at the same time, this would have driven vast amounts of water from the early earth material. This water initially exploded upwards as Noah's Flood. But since the radio decay did not stop with that, the heat again continued to build, melting rocks and building up pools of magma which then erupted in another earth catastrophe the Bible remembers as the time of Babel.
The heating continued, but at a slower pace, in the earth's interior, driving more water out of the rocks, melting more material, and causing the aesthenosphere to become downright slippery with the combination of a high water content and hot magma. It was almost literally 'waiting' for some kind of initial event to start the crustal plates moving. This is rememberd by the Bible as the time of Peleg.
Yes, people saw all of these catastrophes and they are remembered in myth and legend all over the world.
It did not take millions or billions of years. It took only a few thousand. Witness to that fact is the continuing spurts of volcanic activity and earthquakes we still experience.
Yes, the earth once experienced a very warm era -- between Babel and Peleg. But most of it was pretty dry. The large cold-blooded creatures lived primarily where their fossils have been discovered -- near river valleys. These were primarily rift zones with the warm waters still coming up. The Jordan Rift is an excellent example, and the book of Job, in recounting the material about the behemoth and leviathan attests to their living in and around the water.
All of this becomes apparent when we take the data seriously, and part of that data is that which indicates that atomic processes have not been constant throughout history, but have slowed down dramatically. When the correction is made to align atomic and orbital time, the following timeline emerges:
http://www.setterfield.org/timeline.htm
As you go through each of the ages, read the notes at the bottom. Their explanations are thorough.