If the population structure of the earth was a binary tree, where for each element there are two parent elements, then each person 600 years ago would have a billion living relatives. We certainly know that this is not so. The explanation for this phenomenon lies in the principle of “reduction of ancestors.”
If you draw a family tree of one person, then in a strange way it turns out that in each next generation the number of relatives becomes twice as large (parents – two, grandparents – four, great-grandparents – eight, etc.). If we take 20 years for a generation, then five generations pass in a century, which means that for 6 centuries it is 30 generations, which means that every person 600 years ago had 2^30 ancestors, i.e. about a billion people. Needless to say, only about 300 million people lived on the whole earth at that time. Such a structure, where for each element there are two “parent elements” is called a binary tree.
However, as you can see, the world’s population is by no means such a tree; the population structure is more complex – this is a directed non-cyclical schedule. This means that people are much more closely related to each other genetically than they want to expose it. This process of combining the “tree of ancestors” is called pedigree collapse.
True, it is most convenient to investigate this issue on animals. For example, in dogs whose reproductive age is significantly less than in humans. Today’s dogs at the beginning of the 20th century may have ancestors of already 70-80 generations.
If we consider Russia, then about 600 million people lived 600 years ago on its territory (meaning the territory of present-day European Russia, Ukraine, and Belarus). The reduction of ancestors in this way is almost 95%. In general, the probability that two Russian people do not have common ancestors at the time of Ivan the Terrible is very small. However, in connection with the isolation of civilization regions and the estate system in many parts of the world, it makes sense to consider geographic and social genealogy.
In this sense, given the small size of the privileged classes, their reduction is manifested even more quickly and clearly. For example, Carlos II (Charles II), the last Habsburg king of Spain (1661-1700), after whom the famous war for the Spanish Succession began, was not only distinguished by external ugliness, but also by dementia, epileptic seizures, he could not chewing and speaking due to a disproportionate jaw and a giant tongue that prevented food from passing through. In 1550, only two people were his direct ancestors (an ordinary person would have about 50) – so royal families are afraid to dilute their blood. Perhaps they should try to start breeding by budding.
I would like to separately note that the degradation caused by the depletion of the genetic code is characteristic not only for biological species. A good example is the depletion of social systems and political elites, which, without the influx of new drive, are breeding on the parasitically stagnant ideas of maintaining their power. In a word, if you take a closer look, you can easily see the features of Charles II without too much tension in the overstretched power. We call this a fetishized attractor.
Good luck in finding.