What I wrote is what I got from reading the book a long time ago. Of course biology has advanced since the 1970's -- and of course my memory or understanding of

What I wrote is what I got from reading the book a long time ago. Of course biology has advanced since the 1970's -- and of course my memory or understanding of it could be faulty because I read it as a teenager. What you wrote might explain why parents have "favorite" children they're more likely to give their life for.