Today, there are the preserved remains of trees in Northern Ellesmere Island (Canadian Arctic). The climate then (millions of years ago) was tropical-like the present day amazon basin. What was the earth’s climate like in the tropical regions?
Well ralph, a casual Googling reveals:
"During the Eocene period about 50 million years ago, Earth’s climate was warmer on average, but also less seasonal. Tropics-style year-round stability stretched all the way to the Arctic.
“When forests Fluorished On Ellesmere Island” it is likely that other regions were also gleaming white, with few cavities.
Continental drift. I’m more familiar with what happened in the important hemisphere, but I expect the continents moved around a bit up in the northern hemisphere too. So parts of what is now Canada may have been a lot closer to the equator than they are now.
That’s not true in this case. While continents have moved around, the area where these forests have been found was nearly at its present latitude. The polar climate was just much warmer then.
No no, you’re thinking of flouride, which being white helps whiten your teeth. The brown teeth so common in medieval times was due to most people using whole-grain flouride.