There is a very interesting article on the BBC website today. Written by Dr. Yan Wong, it poses the question of how long it takes for the whole of humanity to have a common ancestor. Dr. Wong was initially researching the bloodline between King David and Jesus, but went on to widen the scope of the research to a modern setting.
Recent studies into DNA and the human genome have allowed scientists to speculate about ancestry, including making calculations about common ancestors. The problem arises due to the fact that the number of ancestors we have grows exponentially - 2 parents, 4 grandparents, 8 great-grandparents, etc. Since, according to the Bible, there were 1000 years and at least 35 generations between Jesus and King David, Jesus could potentially have had more than 34 billion ancestors! This is obviously impossible, and is what is known as the "genealogical paradox."
Dr. Wong clarifies this by stating that inbreeding has to be taken into account; in other words certain common ancestors can exist in different branches of your family tree, and are therefore mistakenly counted twice.
Further calculation based on this theory throws up some very interesting numbers regarding common ancestry. For example, it is estimated that the most recent common ancestor of all human beings alive today would have existed only 3000 years ago. That is astounding. Furthermore, this means in turn that somebody alive today will be the common ancestor of the entire population of the Earth in 3000 years time.
Just think of how many genealogical records our descendants will have at their disposal!
I'm not doing the article justice here, so please visit the BBC website to view it in its entirety.