3.5 stars.
The beginning of this book was amazing. The first several chapters were well-researched and provided as much certainty as possible for things with little fossil evidence and happened millions of years ago. However, as the chapters progressed, their quality went down. Steeply. The final few chapters I found were almost complete speculation, and the author came to no conclusions whatsoever. Which is fine. Science does that a lot. But it sure does not make for a good read.
Personally, I think that this author dealt with the gender-diverse topics that invariably come up when talking about female bodies - as well as a cis-woman who does not seem to be deeply entrenched in the LGBTQ+ community. She generally uses terminology the right way (there was only one notable exception to this, and that was with a simply more outdated - rather than offensive - term that I have noticed older people tend to use much more. She is also very clear from the beginning that in most cases in her book the term 'woman' will refer to a cis-woman, simply because not much research has been done on the bodies of both trans men and women. Sooo much more research needs to be done in that area by the way, and reading this book made me realise just how little we know about gender-diverse bodies. Overall, it was really refreshing to read a feminist book about sex that was not written by a TERF. It has given me hope in humanity again.
One of the really positive things that stuck with me and was totally worth reading through all the slog at the end of the book was the fact that female bodies are not constantly preparing themselves to be pregnant just to make babies, which is what is commonly taught in sex ed classes around the world. Instead, a much more likely situation is that the body knows that it physically can get pregnant - not that it should - and decides to prepare so that if pregnancy did occur, they would not die.