Seth Godin is far from the first person to refer to the amyglydia as the "lizard brain". I really couldn't tell you who coined that term or when, but I was seeing it when I was reading about the brain as a kid back in the seventies.

Also I am in my early 40s and am not even beginning to turn into my parents, for what that's worth.

I believe that the brain changes between the age of 15 and 30, and I also believe that most people's lives changes between those ages. I'm not so convinced that the former cause the latter, especially without any kind of scientific evidence. There are a lot of things that change socially over that time period.

The author's take on the amygdala is also pretty weird. Sleep, hunger, and sex are all functions generally associated with the hypothalamus, not the amygdala.