" Ruth McQuillan and a massive international team scanned the DNA of 35,000 people across twenty-one European countries, and looked for identical genetic variants on both chromosomes across the whole genomes, thereby identifying consanguinity. The difference between those with first-cousin-like inbreeding and outbred individuals was, on average, three centimeters. Socioeconomic factors played a massive part, and were accounted for in the final analysis. The inbreeding depression on one of the simpler metrics of humans is just over an inch. The black Tinkler winna "

― Adam Rutherford , A Brief History of Everyone Who Ever Lived: The Stories in Our Genes