@iuwclurker Taking this off thread to address your curiosity without further mucking up the Ukraine thread.
We can learn a lot about how people are related to each other generally through virtually any genetic comparison. If a group of people all share the same discrete set of single nucleotide polymorphisms (individual changes in a single nucleotide at a specific point in the genome), then they are very likely closely related. However, for purposes of genealogy, this can easily get messy, because 45 of our 46 autosomes can pass from either the mother or the father, and can also switch genes back and forth during meiosis, in a process called recombination. This quickly can lead to genetic drift, further blurring genealogical lines. There are two special cases, however, that are useful for genealogy: Y-chromosomes and mitochondria.
Y-chromosomes are only passed down the male line, because they can only be supplied by a sperm. Mitochondria are only passed down the female line, because they don't exist in sperm, and therefore can only come from an egg. So if two people have identical mitochondria, they have a recent common female-line ancestor, and if two men have identical Y-chromosomes, they have a recent common male-line ancestor. With the Y-chromosome, we can only directly test males, but we can also count how many sisters and half-sisters those males have by the same father, and, at any rate, since people tend to have male and female offspring at roughly the same rate, if x% of the male population shares a common male-line ancestor, it's likely that very close to x% of the female population consists of sisters and paternal half-sisters and various forms of cousins who also share that same ancestor (that is to say, females whose father also had the same Y-chromosome).
Long story short, what the study you didn't get to fully read about actually said was that, among people living in the former Mongol territories, about 8% of males (and therefore, most likely, about 8% of the entire population) have a relatively recent male-line common ancestor. An argument has been put forward for the case that said ancestor is Genghis Khan himself, although without his remains or the remains of someone verifiably known to be related to him in the direct male line, we can't say for certain that it was actually him.
We can learn a lot about how people are related to each other generally through virtually any genetic comparison. If a group of people all share the same discrete set of single nucleotide polymorphisms (individual changes in a single nucleotide at a specific point in the genome), then they are very likely closely related. However, for purposes of genealogy, this can easily get messy, because 45 of our 46 autosomes can pass from either the mother or the father, and can also switch genes back and forth during meiosis, in a process called recombination. This quickly can lead to genetic drift, further blurring genealogical lines. There are two special cases, however, that are useful for genealogy: Y-chromosomes and mitochondria.
Y-chromosomes are only passed down the male line, because they can only be supplied by a sperm. Mitochondria are only passed down the female line, because they don't exist in sperm, and therefore can only come from an egg. So if two people have identical mitochondria, they have a recent common female-line ancestor, and if two men have identical Y-chromosomes, they have a recent common male-line ancestor. With the Y-chromosome, we can only directly test males, but we can also count how many sisters and half-sisters those males have by the same father, and, at any rate, since people tend to have male and female offspring at roughly the same rate, if x% of the male population shares a common male-line ancestor, it's likely that very close to x% of the female population consists of sisters and paternal half-sisters and various forms of cousins who also share that same ancestor (that is to say, females whose father also had the same Y-chromosome).
Long story short, what the study you didn't get to fully read about actually said was that, among people living in the former Mongol territories, about 8% of males (and therefore, most likely, about 8% of the entire population) have a relatively recent male-line common ancestor. An argument has been put forward for the case that said ancestor is Genghis Khan himself, although without his remains or the remains of someone verifiably known to be related to him in the direct male line, we can't say for certain that it was actually him.
