the gallery has far too small a number [25!] of individual portraits for me to draw any statistically conclusions.This is a good start, but there are possibly two more apologies that might be expected by any reader.
So the USA is really 25 people selected for various reasons, but most often convenience and availability, What about DNA? Well, the book discusses DNA in several places, in between a smattering of world history, USA travelogue, and miscellaneous anecdotes. Many of these were genuinely interesting, while others were redundant to an educated reader. Written in the first-person, much comes across like a narcissistic Oxford Professor.
So not really USA, and not really DNA. What is the third apology. The third apology is alluded to throughout the book. This is that the topic itself and the crude analysis is inherently racist. In between explaining why older attempts at such analysis were crude and inaccurate and, therefore, racist, the author seems to miss the irony that the proffered book is just another racist analysis masquerading as the latest science.
My recommendation is that if the title intrigues you, don't read this book, but if you have a voyeuristic interest in up-to-date racism, this is the book for you.