3 ms·

How is a family TREE not a tree

• knappa 4y ago
  Eventually your (for example) great*N paternal grandfather is going to show up on your mother's side, forming a loop. That's just due to bounds on the human population and how the number of labels for previous generations grows exponentially backwards in time.
• robocat 4y ago
  The word tree[1] has a specific meaning when talking about computer science (recursion). An idealised biological family tree is a DAG (directed acyclic graph[2]), because there are cross linkages creating common ancestors, although I am also presuming we define when to stop adding nodes. An actual family tree is not even a DAG because the nodes are unknown, and “parents” is an extremely fuzzy concept. Where does adoption fit it? What about step-parents? How do you record uncertainty? Etcetera. One of my friends in another country had a kid with her first cousin, and parents can be more closely related biologically. It is less than one hundred generations before we find a single common ancestor to everyone alive[3]. Also see [4][5]. Regardless, anyone that thinks using a family tree as a teaching example for children should have a reëducation holiday </unfunny-black-humour>. [1] https://en.wikipedia.org/wiki/Tree_(data_structure) https://en.wikipedia.org/wiki/Tree_(data_structure) [2] https://en.wikipedia.org/wiki/Directed_acyclic_graph https://en.wikipedia.org/wiki/Directed_acyclic_graph [3] https://www.scientificamerican.com/article/humans-are-all-more-closely-related-than-we-commonly-think/ https://www.scientificamerican.com/article/humans-are-all-mo... [4] https://en.wikipedia.org/wiki/Mitochondrial_Eve https://en.wikipedia.org/wiki/Mitochondrial_Eve [5] https://en.wikipedia.org/wiki/Y-chromosomal_Adam https://en.wikipedia.org/wiki/Y-chromosomal_Adam