There is something I want to share with “fellow Europeans”, and it is something hard to describe. It is to, in a moment, “feel” the past. How can I convey this? How can I show this?
Around 7700 BC, white skin had “reached fixation”, or the highest prevalence in the genome until today or some later decline, in modern-day Sweden. Some time around 3500 BC, white skin reached fixation in the rest of Europe.
I don’t say this because white skin is super-important (though melanin is a hormone and it’s absence will have causal effects on behavior), but just to give an idea of how quickly a genetically-based trait can spread. The late Henry Harpending in his book “The 10,000 Year Explosion” explains introgression, whereby the genes of a different population can enter another population, and then those genes get selected upon, the result being that a trait could spread through the population faster than you would expect from traditional natural selection.
For example, a mutation that increases fitness by 10%, if it came into existence in a single person, would come to dominate a population of 149,000 people in about 125 generations. If each generation is 25 years, this would be 3,125 years. And that’s assuming the mutation only happens in one place. If the mutation for light skin or ability to drink milk into adulthood independently crops in 10 places, and has a 10% reproductive advantage, then it would “fix” (reach nearly 100% prevalence) in a population of 1.49 million in 3,125 years. If it independently pops up 100 times, 14.9 million.
And since most people at the time successfully had between 1 and 3 children, factoring in the number who had zero, a 10% increase in reproductive fitness wouldn’t be noticed. If people who could tolerate lactose had 2.1 kids on average versus 1.9 for those who didn’t, what would this look like in practice? Well, in 10 households with lactase persistence, 9 would have two children, and 1 household would have three. In 10 households that did not have adult lactose tolerance, they would have 9 with two children, and 1 household would only have one. Nobody who wasn’t keeping records and looking for these kinds of correlations would even notice.
But the important takeaway is that evolution happens fast – or at least the “small” things such as the range of cognitive differences between what are considered functional humans.
The Collapse in Homicide
From 1300 to 1900, there was a collapse in homicide rates in most European countries.
In 2003, Manuel Eisner did amazing work estimating the homicide rates in historical homicide rates in England, Belgium & Holland, Scandanavia, Germany & Switzerland, and Italy:
Historical Homicide Rate in England (Eisner 2003)
Historical Homicide Rate in Holland and Belgium
Historical Homicide Rate in Scandanavia
Historical Homicide Rate in Italy
Historical Homicide Rate in Germany and Switzerland
Remember these are all logarithmic scales, and so the decline in from each y-axis interval is a 10 times decline….[ ]