I was working with some people who had a school

I was working with some people who had a school. They asked me to teach a class about evolution. That was a topic of which I was knowledgable. I needed to be able to walk into the classroom and be handed an outline, and then speak to that outline. That is what I did, successfully. I had found that when I knew a topic well, that speaking extemporaneously was not a problem for me.

The whole topic of the history of the Earth and evolution was a subject that had long interested me. The reality is that evolution has not been a nice, straight-line process, with incremental changes along the way. Instead, the Earth has been subjected to periods where there was increased radiation, presumably from the Sun, which caused rapid mutation. When the radiation died down to a more stable level, the new variations bred and the stable results would survive.

Another factor has been the periodic cataclysms that have wracked the Earth. Most have been from collisions with asteroids, or large metereorites. Some of the effects have been quite dramatic, such as shifts in the axis of rotation of the Earth, and changes in the magnetic poles. There may be something to the concept, rather a fringe idea, that the Earth's crust could "slip". That could account for the sudden freeze that caught the large animals and froze them, in the last 100,000 years.