The core “argument,” if it can be called that, of part II of Adam Rutherford’s How to Argue with a Racist, is that race is not real because everyone is related.

Ancestral belonging and genealogy are things that fascinate us all, but racists especially: genealogy is possibly the second most popular pastime in the UK (after gardening), and the first in the US. Many of the arguments put forward by racists centre around belonging to specific demographics, the othering of different groups and the displacement of people. Many nonracists are also concerned with immigration in the modern era, but few express the sense of a people being replaced or a culture somehow being weakened. It is never clear what is being threatened when, for example, white supremacists express fear of the demise of Western culture. I don’t know what Western culture is, because it’s very clear to me that my culture is not the same as the culture of other people in my street, postcode, city, country or continent.

Go back a few centuries further and we reach a mathematical certainty referred to as the genetic isopoint. This is the time in history when the entire population is the ancestor of the entire contemporary population today. For the people of Europe, the isopoint occurs in the tenth century. In other words, if you were alive in the tenth century in Europe, and you have European descendants alive today, then you are the ancestor of all Europeans alive today (we estimate that up to 80 per cent of the population of tenth-century Europe has living descendants). Another way to think of it is like this: one branch of a family tree of two first cousins crosses in a shared grandparent; one branch of all European family trees cross through one individual in 1400 CE; at the isopoint, all branches of all family trees cross through all people for that population.

I am well aware, having said these facts to students and public audiences hundreds of times, that this is a brain-scrambling concept, because it is so far from our casual assumptions and thoughts about ancestry, family trees and identity. It certainly doesn’t sound right, and is further confounded as a concept by the calculations of the global isopoint – the year in which the population of the Earth were the ancestors of everyone living today. This, astonishingly, comes out at around 3,400 years ago. Everyone alive today is descended from all of the global population in the fourteenth century BCE.

As is apparent above, Rutherford isn’t arguing as much as he’s just misrepresenting the evidence and babbling about its extreme complexity, just like in part one. By my count, the string “complex” appears about 20 times in part II alone.