Adam of Eden is my 78th grandfather – I had no idea. Apparently William Hilton of York, Maine has a recorded pedigree that spans further than I had imagined.
What you all are attempting here reminds me of my Chadbourne ancestor who in 1893 helped organize the ambitious project of the first Parliament of the World's Religions in Chicago and sponsored the travel and attendance of Vivekananda to represent Hinduism. A speech written by one of my cousins, Mary Baker Eddy, was also read to represent Christian Science. Other attendees included representatives of Southern Buddhist, Zen, Jain, Islam, Bahia and others. The fruits of this Interfaith dialog are still ongoing. And it is fascinating to see how many parallels exist.
My field is molecular genetics but the word genetics has the same root as the word for genealogy meaning race or kind. And there is a biological definition of the word genealogy meaning a group of individuals or species having a common ancestry as in “The various species of Darwin's finches form a closely knit genealogy.”
Sharon Doubell raises an interesting question – Who is our great-X Grandparent who gave us our Y chromosome? In fact I am a small financial donor to a project that hopes to answer this question. If we look at the biological genealogy of all Y chromosomes of living homo sapiens was can see that they all descend from a common Y chromosome of the haplotype A0. We can also determine that the A0 male progenitor lived well over 100,000 years ago. But we have recently discovered one small exception. There were at first two men discovered who carried a Y Chromosome that belonged to a pre-human haplotype we now call A00. They inherited their Y chromosome not from the A0 progenitor but from some species in the genus homo from which A0 sprang. The current research is to study all extant examples of A00 and we have recently discovered what appears to be a Nexis of individuals living in Cameroon who are A00. And so we are sampling males in Cameroon and comparing their SNPs to learn as much as we can about our pre-human Y chromosome origins. So to answer Sharon’s question – yes our Y chromosomes came from a homo sapien who had an A0 Y chromosome well over 100,000 years ago. He would have had many cousins who died out leaving us with a genealogical bottleneck for living descendants. This homo sapien in turn was a descendant of a pre-human species who carried an A00 Y chromosome. And some A00 Y chromosomes still exist! And we are still learning…
When we speak about populations we speak about the frequency of “alleles” within the population such as accumulated SNPs and STRs which everyone here is familiar with. And we compare these derived states against the state of the ancient state of these same markers. Novel derived SNPs and STRs accumulate over time and each one has a point of origin in time and space (and there may even be parallel identical derived states of different origins). So as we look at each of these derived alleles it might be best to think of them as each having their own progenitor with a different date and place of origin. So while the A0 Y chromosome has one specific date and place of origin that is not the same as the origin of any other marker necessarily. Some of these markers (in their ancient state) originated before our species. Others are quite recent. And we keep re-mixing and re-shuffling these markers over time. So what I am saying is each genetic marker has an origin and an ancestor associated with that origin. But we as carriers of many markers have many diverse origins of our genetic state.
It is vital to distinguish the concept of a common ancestor of the state of a marker or the state of a group of markers such as the A0 Y Chromosome well over 100,000 years ago and concept that any two people may share at least one common ancestor say 2,000 – 4,000 years ago for example. Just because you and I share at least one common ancestor about 3,000 years ago does not mean that person had the same Y chromosome haplotype as you or I for example (assuming this person was male). In fact it is possible that his Y haplogroup went extinct. So instead we may want to think of the latter as the “last common ancestor” I shared with my most distant cousin regardless of if we inherited any derived states of markers from that last common ancestor. But I also have a last common ancestor that I share with everyone whose ancestors inherited a specific derived state that occurred at a specific time and place. For example I know of a specific SNP on my Y chromosome that must have occurred in a specific ancestor, Eli Forbes Baker, about 200 years ago that he passed on to all his male children. He is the last common ancestor for all of his male descendants whose ancestors carried this trait. But other traits are 50,000 years old or 100,000 years old and for each of these traits there is a “last common ancestor.” The further we trace our ancestors back the more we find that they had the ancestral state of each marker we follow. Eventually we get to a very small population very long ago.
I’ll add to this that the ~3,000 year old estimate for a last common ancestor has some “assumptions” that should make you cringe a bit. It does to a degree try to factor in random breeding assumptions and geographical isolation. But just how isolated were the Aboriginal Australians from the Aboriginal populations from Europe or South America? Did they really share a common ancestor 2,000 – 4,000 years ago? Probably not! So while this is heuristic and we can learn something from the method employed we need to carefully deconstruct the assumptions made before we employ this method to our own research because clearly we did not have random mating and we did have some very geographically isolated populations on this planet.
