I have friends and relatives with an interest in genealogy. I've explored it a little, not so much out of family pride, but I'm kind of interested in how or why people ended up where they did historically. But that's not really my question. I noticed that people seem much more interested in two lines lines of descent - the mother's, mother's mother's mother, etc, and the father's father's father etc. even though they don't really contribute anything more to your history or genes than your mother's father's mother's mother' father. I guess from a science point of view, there's the preservation of mitochondrial DNA and the Y chromosome, if you want to have your DNA analyzed and trace haplogroups, but even people who aren't interested in the science end of it seem more attracted to those two lines.