Looks really nice. I wish that I had more time to really study it.

A couple of typos:

The link to the pdf file above has a typo, it has ".pf" for the suffix, not ".pdf"

> Sometime between 3.5 and 2.6 billion years ago ... started dumping a deadly gas into the atmosphere: oygen!

Oy that oygen.

Last point. It may be by your design as an author, but the ending, which refers to the present day conditions, is terse -- it left me waiting for the next slide. I suggest a slide or two more with some of your key observations about the current challenges we face -- in relation to the large sweep that you describe -- as a way to close it out.

Good luck with the talk.