I have been reading most of the book "The Invisible History of the Human Race," written by the Australian journalist Christine Kenneally. It is a book about how the combination of DNA and history shape our identities and our futures. Many of our traits depend on random events in the past, migrations and human decisions taken centuries ago by our ancestors. Culture influences DNA because decisions such as migrations create bottlenecks in the sense that small populations leave a place and then expand and reproduce somewhere else, where they meet others. For example, most non-African humans have some Neanderthal ancestor. DNA also influences culture because physical traits have been used to stigmatize some groups and discriminate. With modern technologies, it is possible to know more about the past of current groups. It is very interesting that our genetic background is necessarily diverse and complex, difficult to classify, the result of many previous combinations of genes. However, given the limitations of our rationality, we tend to think of human groups as discrete groups, with sharp distinctions between us and others. I found the case of the Melungeons group in Tennessee very interesting. The origins of this group are largely mysterious. They have darker skins than whites, as well as other distinctive physical traits, but they are not African or Native Americans, although their ancestors probably combined with these. The legend says that they may be the result of some small group from the Mediterranean arriving to North America at some point in the remote past. The book also reviews the work of economists such as Nathan Nunn and Karla Hoff, and economic historians such as Voth and Voigtländer, who have specialized in the enduring effect of the past on the current beliefs, choices and preferences of populations. For example, regions of Africa that were more affected by slavery showing lower levels of truth today, or the caste system in India projecting a long shadow up to the present although its legal aspects have been eradicated, or parts of Germany where there had been more progroms in the Middle Ages having been more prone to anti-semitism in the twentieth century.