So, at some point there appeared multiple bears at the same time? Or should I bear in mind that we can't define any species accurately and clearly?
What say you about this:
Scans of Earth's deep interior reveal a vast water reservoir beneath Asia that is at least the volume of the Arctic Ocean.
www.livescience.com
It is fascinating how you can believe they have moved.
Me? That's what any modern, scientifically literate person accepts, because of the evidence I referred you to. We see them continuing to move as we speak, by several cm/yr.
A population of creatures increasingly resembling bears appeared over time, from a population of bear-like ancestors.
As for water inside the Earth, yes we know, but it is not free water. I'm a chemist. The water referred to is present as hydrated minerals. Water from the oceans is entrained with subducted crust at the ocean trenches and this water becomes chemically combined with the minerals to form new minerals. This leads to altered mechanical properties of the rocks, hence the effect on seismic waves mentioned in your link, and also tends to lead to minerals with lower melting pints. The lower meltiong point is what explains the volcanies we see behind ocean trenches. Japan is an example. What is interesting in this article is the presence of hydrated minerals relatively far from subduction zones. Later work confirms this is quite general, for example here:
There’s as much water in Earth’s mantle as in all the oceans. leading to a reappraisal of the amount ot water locked up in the earth's mantle.
But do not delude yourself that this is free water. It is not. The minerals in which it is present are solid and hard, just not as hard and not as difficult to deform as related anhydrous minerals. Perhaps you remember blue copper sulphate from school. That is CuSO4.5H2O, a hydrated form. You can heat it to drive off some of the water, generating white CuSO4. H2O. But blue copper sulphate is itself a hard solid. The same thing is going on here.
There is no mechanism that can suddenly release all this bound water and then suddenly absorb it all again, if that's what you are thinking. Of course, if you are into miracles, anything is possible - but then why bother with looking for the water in the Earth? God could have poofed the extra water into existence and then poofed it away again.