I might suggest that an article by Alva Noë in the NPR web site should be required reading for all genealogists. He writes:
- You share no DNA with the vast majority of your ancestors.
- You have more ancestors — hundreds a few generations back, thousands in just a millennium — than you have sections of DNA.
- You have 64 great-great-great-great-grandparents — but if you are a man, you share your Y-chromosome with only one of them.
- The amount of DNA you pass on to your descendants roughly halves with each generation. It is a matter of chance which of your descendants actually carry any of your DNA.
- It can be demonstrated that 5,000 years ago everybody alive was either the common ancestor of everyone alive today, or the common ancestor of no one. At this point in history we all share exactly the same set of ancestors.
In other words, everyone alive today is related to everyone else alive today. We are all distant cousins of each other.