|MadSci Network: Genetics|
Well in all my searchings I have found nothing that indicates any special reasoning behind the shapes for either of the sexes in a pedigree. From what I can tell it was just an arbitrary and easy way to visually tell the difference between the sexes on the pedigree. After the first group of people represented the pedigree like that using circles and squares others just copied it. This is usually what happens in science. The first people to do something in a particular way usually set the standard and others can copy, use, and augment it. This arbitrary format has become a "legacy" of sorts. Not every representation in science has a "meaning". Sometimes, it just comes right down to the utility of representing objects or ideas in the best visual way. Since we humans are visual creatures we need obvious and quick ways to discern various subjects on paper (or screen). For example, if you use a spread-sheet program to make a graph you may choose 'X's and 'O's to represent your points because they are the most obvious to discriminate (as opposed to using both a square and a rectangle to represent different measures). This is the best answer I can come up with. I have been unable to find any "original" work that used squares and circles in a pedigree for the first time. So, I suspect it is for the reasons I stated above.
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