Where to possibly begin there, other than "biology, best to first try learning it before you dismiss it" anyway.
I assume by "tangible evidence" you mean nobody has dug down, found a skeleton, dug down a bit more to rocks from an earlier age found a different skeleton that was slightly different.... and ? million years ago here is the ape, or if you prefer the lack of a missing link/chain. It would be nice to see such a thing but comparative genetic analysis of apes/primates/Simiiformes and humans, retroviruses (viruses that get attached to DNA and replicated alongside "proper" DNA) all that jazz means there is no doubt in that one, evolution itself has been demonstrably observed in a lot of things.
On the organs thing had you said something like the evolution of the eye we could have possibly had a somewhat interesting discussion, even if it is more of a thought exercise used to teach people evolution and some of the more interesting concepts like parallel evolution. Anyway it sounds like we will have to overcome the puny human mind issue with large numbers (100000 seconds is a bit more than a day, 10000000 is 115 days), then we get to consider that if the human reproductive cycle (one of the longest in nature) is some 20 years then the several billion years that life has been on earth has been enough for a few such life cycles, now humans were not around that entire time but given you can stick a pig heart in a human and have it work then it is clear other animals have similar functioning organs, and if not then that they function in much the same way, use much the same chemicals and so on would.
Seriously though pick up a book on biology. There are many unanswered issues within it but your two examples are not even close to being ones.