Why Families That Go Back Many Generations Have Far Fewer Ancestors Than They Expected

Cameron Duke of MinuteEarth explained The Ancestor Paradox, a simple genealogical term that states that while a family may go back many generations, some of their forbearers may have been related to one another, thus reducing the limbs on a family tree.

To make sense of this, let’s say for example, I dunno, that your parents are first cousins. …That would mean that two of your grandparents are siblings.Since siblings have the same parents, and therefore the same ancestry, a bunch of these ancestors are duplicates; we can really just count them once. Going back to our 37 generations thing, that’s more than 34 BILLION ancestors we would  no longer be counting!

This is due to inbreeding, which was very common in certain eras due to small communities, pedigree maintenance, and “kissing cousins”. This led to a reduction of ancestry or pedigree collapse, as the shared ancestors could only be counted once.

And our family histories are full of lots  and lots of inbreeding. That might sound pretty gross to you and me, but mating with relatives  hasn’t always been frowned upon – heck, Albert Einstein married his first cousin.And certain royal families actively encouraged inbreeding.  But the biggest reason for all this inbreeding  is that, throughout most of human history,  we lived in small groups with limited  babymaking options…