

Pedigree Collapse - jfmercer
https://en.wikipedia.org/wiki/Pedigree_collapse

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nvader
I've encountered this concept before, but have not been aware of its name.

Taken to its very extreme, we have pedigree collapse where a single individual
occupies all male spots:
[https://en.wikipedia.org/wiki/Y-chromosomal_Adam](https://en.wikipedia.org/wiki/Y-chromosomal_Adam),
and a single female occupes all female spots,
[https://en.wikipedia.org/wiki/Mitochondrial_Eve](https://en.wikipedia.org/wiki/Mitochondrial_Eve)
Interestingly, these happened at different points in history.

~~~
NAFV_P
[http://www.dailymail.co.uk/sciencetech/article-2930277/Eleve...](http://www.dailymail.co.uk/sciencetech/article-2930277/Eleven-
fathers-Asia-800-million-modern-men-descended-ancient-leaders-including-
Genghis-Khan.html)

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jfmercer
Of particular interest to me was how pedigree collapse transforms our family
trees from exponentially growing binary trees into directed acyclic graphs.

We are accustomed to thinking that, because we have four unique grandparents,
we must have eight unique great-grandparents. But this is not always so. For
example, if our grandparents are two brothers who married two sisters, then we
have four great-grandparents, not eight.

