Book about a man who is billions of years old?

[LasseHolst]

I need help finding the title of a book.

It's about a man who is several billion years old. Each chapter starts with a scientific facts, and so says the protagonist "Oh yes, I remember it very well," and then there's a little story about something he experienced during a specific event in world history. For example, there is a story attached to the time where the small invertebrates (or what the small water animals are called) begins to walk on land. An invertebrate falls in love with one of the animals on land. I do not remember much more than that, but maybe anyone can recognize it?

Thanks