Genealogical is not Genetic

So I had a very surprising experience recently that ended up revealing a great deal to me.

It turns out that there is a large body of mainstream scientific work that is not known to most Evolutionary Creationists. I did not know this at the time, and was very surprised by some of the responses I got to mentioning it. At the time, this was caught up in conversations about theology and Adam, where this is surely relevant. But the theological implications are beside the point if we are not working from the same understanding of the science.

I wanted to try again, this time without bringing (until I am forced) theology or Adam into the conversation. There should be no theological objections to explaining a mathematical theory and how it makes sense of the genetic data we see.

The key missing pieces, it seems, is working knowledge of the science of genealogical ancestry, which is very different than the science of genetic ancestry. Even if you do not understand the distinction yet, please go with me for a moment and just trust that there is. So do not treat genealogical and genetic as interchangeable. They are not. They are totally different concepts.

To get started, I am going to make several very surprising claims based on this body of work. I will not provide the citations on the outset, but I have them. This list of claims I can back up with (1) math, (2) published papers, and (3) intuitive explanations. I’m curious what you will find most surprising and want to get more information about.

  1. The vast majority of genealogical ancestors are NOT genetic ancestors.
  2. Universal genetic ancestors (of all living people) appear about 200,000 to 300,000 years ago, but Universal genealogical ancestors (of all living people) appear in 1/100th the time, about 3,000 to 2,500 years ago.
  3. Genealogies (i.e. pedigrees) are unobservable in genetic data farther than about 1,000 years in the past.
  4. We have billions and billions of common genealogical ancestors, and this number only grows with time.
  5. We have only one Y-Chromosome Adam ancestor (a type of genetic ancestor), and the identify of this individual changes over time.
  6. If we go back far enough (about 5,000 to 15,000 years), every person alive before then is usually either (1) a genealogical ancestor of every human alive today or (2) a genealogical ancestor of not even one human alive today.
  7. It is impossible for science (genetic or archeological) to demonstrate a population on earth was entirely isolated, with no interbreeding, for a long period of time.

And a few additional assertion that do dip into theology. If you disagree, please cite some verses and explain how (if all the science I have given above is correct) that your objection is valid.

  1. There is no genetic claims in Scripture if #1 above is true, but there may possibly be genealogical claims.
  2. There is not scientific way to define the “mankind” of Scripture. Are Neanderthals included? Are Denisovans? Are ancient humans (200,000 years ago)? There is no guidance in Scripture or science. We cannot know.

Okay, with that, I’m curious your thoughts.

Dr. Swamidass, I’m interested in considering your post in more depth. Can you help a layman out and give me the bottom line on the difference between a genealogical ancestor and a genetic ancestor?

The bottom line is that they are two very different concepts that describe things that behave in very different ways. If we do not understand these differences, we will end up missing what science and does teach about our origins. We will miss how evolution presses on theology.

What I mean is, in the term ancestor, aren’t both genetic ancestor and genealogical ancestor inherent? How can an ancestor be one but not the other?


The distinction that you point to is important, and I want to add that Genesis goes to great lengths to show how God began to deal with human beings (Adam and Eve), and everything else (including questions that stem from genetic diversity) are either peripheral or ignored.

Scripture traces the genealogy back to Adam for a very important theological purpose - as this provides the lineage of those who understood God’s purpose and some (such as Noah and Abraham) found favour in God’s site. Ultimately, the Gospel shows us that Christ as the Son of Man is part of that genealogy - it cannot get more central to the Christian faith that that.



I did a piece on the “Most Recent Common Ancestor” work even before I started The Hump of the Camel, back in early 2011 (and it was prompted by a comment here). My piece, though I’d have developed it differently now, summarises some of the Most Recent Common Ancestor research, gives some links to original papers and ventures into a few theological implications. It may help confirm what you say here.

All I’d add here is that the surprising results of this genealogical ancestry question (we really are all descended from Charlemagne…) also remind us that the human race is a very dynamic unity not only genealogically, but culturally. That is, the fact that one can establish pretty well that even Australian aborigines or Andaman Islanders have not been reproductively isolated also shows that culture permeates the world, for good and ill alike.

Someone invented the bow and arrow back in palaeolithic times, and even then the idea was around the world within a few centuries, through trade, warfare and so on. Bearing in mind that who we are as people is largely conditioned by our enculturation by those around us, we therefore have more than one model for the unity of the human race, over quite recent times, which is hidden if we only look at genetic issues. It’s not implausible that if one person learned sin, the idea might very soon become as universal as fire.

On your final point, about who gets included in the mankind of Scripture, we really need to be careful to avoid simply mapping biological categories to revealed Scripture. On the one hand, the gospel makes it plain that as far as evangelism/judgement etc go, the present cultural unity that we easily recognise is what matters. (We don’t have to decide whether to try to teach Denisovans to read the Bible!).

As far as what Genesis, for example, means by “adam” (man), we need to remember that, culturally, the ANE could often be quite selective in its use of “man” - some cultures used it only of their own nation, because that was the subject that interested them. And we should also remember, theologically, that there is a sense in Scripture that true humanity involves some kind of relationship with God - the story begins with a man placed in a garden for a specified job by God, rather than (say) the discovery of religion by an inquisitive mind.

So however we interpret those first chapters, we should never replace a partly spiritual concept of man with a merely biological one and build our theology on the latter.


Clearly, if one counts back ones great-great-etc… grandparents, multiplying by two each time, there comes a time, surprisingly recently, when the number of ones ancestors mathematically calculated exceeds the population of the earth by many times. This is easily explicable in that many of the calculated individuals are in fact the same person. The corollary is that broadly speaking everybody on earth today is more or less equally descended from everybody on earth then. Excluding, of course, the childless.

Therefore, there was a time not so long ago - ten to a hundred thousand years or so - when everybody on earth then (and there were several millions of them) was the ancestor of everybody alive today. At that point, genealogy breaks down completely as a discipline.

Some people would like to point to a couple of these people and say: ‘maybe these two were Adam and Eve, since everybody is descended from them,’ thus giving a relatively recent possible date for the Garden of Eden. However, to do so would be a serious mistake, as we can only claim that everybody alive today is descended from them, not that everybody who ever lived was descended from them. Just because you and I must be descended from them does not mean that Jesus and Caesar must both be descended from them. They would have to go further back in time, to find an ancestor common to them both.

To find somebody who was the ancestor of everybody who ever lived is much more difficult, and to my mind evolutionarily unsound. That would require that the entire genetic diversity of the human race must have been included within a single pair of genomes, which various studies suggest is difficult to maintain.

So, Josh, for any individual, all his ancestors are both genealogical and genetic, but in considering groups of people, it is useful to make a distinction between them.


This is false on several points.

  1. Genealogical science does not break down here, but gives us a way to estimate when it happens. It does not break down at all.

  2. The Identical Ancestor Point (IAP) is not 100,000 years ago, but almost certainly less that 15,000 years ago, but maybe as recently as 5,000 years ago.

  3. At the IAP, there are two groups (1) those that are ancestors of everyone alive today (as you mention) and (2) those that are ancestors of no one alive today (you do not mention them).

Your claim is not supported by the science and it is reading things into scripture. How do you define “everybody”? We can also determine an IAP any group of people, but which group of people are"everybody"?

This is not correct. You have to define "everybody, which is not possible to do with confidence.

This is false. Remember I wrote…

This is a very important question, where so much confusion arises.

  1. “Genetic ancestors” is a term that is scientifically applied (usually) to DNA sequences, not individuals or populations. We say that the genetic ancestor of, for example, the Y-Chromosome is the Y-Chromosome of the individual (Y-Adam) from whom all Y-Chromosomes descend in an unbroken line. However, my Y-Chromosome does not have an ancestor in my mother’s genome.

  2. “Genealogical ancestors” is a term applied to individuals, and follows (almost) our commonly understood meaning of ancestor. In Scripture, adoptive children are also considered part of genealogical offspring too (see Joseph and Jesus), which is different than our understanding now. So even this is not a precise map, because in science we do mean biological descendents.

With this, my mother is no the genetic ancestor of my Y-Chromosome, but she is my genealogical ancestor. If I go back about 50 generations, almost none of my genealogical ancestors are genetic ancestors of any of my DNA.

Thank you for replying, but I think we are talking somewhat at cross purposes, as I agree with everything you say, and said in your first post!

  1. When I say that genealogy breaks down as a discipline, I ought to explain that I carry out a lot of genealogical research, and enjoy producing family trees which go back into the past, with ever increasing numbers of ancestors. Every now and then, when cousins marry, the family trees get a little untidy, when somebody’s great-great-great grandfather on his mother’s side turns out to be also his great-great-great-grandfather on his father’s side or something like that. If one could ever construct a family tree for everybody alive today, the upper branches would get so entangled, with every single person alive then being the ancestor of every single person alive now, that the concept of a family tree would lose all meaning and further genealogical research would be pointless.

  2. Yes. I rather hedged my bets in saying between ten and a hundred thousand years ago. It rather depends on the reproductive isolation of, say, the !kung and aboriginal Australians. I didn’t know enough about it to be any more definitive. I still don’t.

  3. Yes. Again. I did mention “excluding the childless”, but of course that could extend to people who did have children but no grand-children, or grand-children but not great-grand-children and so on.

  4. Um. I’m not sure what you mean by “which group of people are everybody?” I guess I could have specified Homo sapiens. Perhaps you are referring to the Creationist idea that some early humans were descended from the biblical Adam and Eve but others weren’t. This seems to me a rather forlorn attempt to maintain the literal historical truth of Genesis, and to my mind founders both scientifically and, more importantly, theologically. It is certainly not upheld by the Catholic Church, to which I belong.

  5. [quote=“Swamidass, post:8, topic:35659”]
    The vast majority of genealogical ancestors are NOT genetic ancestors.
    [/quote]Yes, again. I did not appreciate that by genetic ancestors you meant ‘the ancestors of particular genes’. Sorry for my confusion.

Perhaps there are still those confused by these two terms:

Genetic Ancestors
Genealogical Ancestors.

As the de facto family genealogist who frequently has to explain such matters, let me make an effort to do so here:

Genealogical Ancestors is purely a mathematical application of inheritance of “blood” or “genes” based on the idea that ones genetic factors can be divided into infinitely fine proportions, with perfectly equal proportions being shared amongst siblings, and then cousins, and then 2nd and 3rd cousins. For example:

In this common format for showing ancestry of a single individual, concentric rings of pie slices become cut thinner and thinner, with each generation. Every once in a while, as in more than 20 states in the United States, 1st Cousins (or 2nd or 3rd cousins) marry and have children. When something like this happens, one wedge of the pie is suddenly exactly the same as the another wedge!

In this case, I have made the Blue wedge the exact same people as in the Red wedge. This is what is mean when genealogists describe a “Pedigree Collapse” of a part of a family tree. Pedigree Collapse to one extent or another is virtually unavoidable, given enough time. There are millions and millions of descendants of Charlemagne. And every time 2 of them find each other and produce offspring (totally ignorant of their common ancestry or not), there is a small amount of Pedigree Collapse that occurs.

Genetic Ancestry is even more “rocky” - - because unlike the simple math of dividing 1/2 by 2, and then dividing 1/4 by 2 and so forth, the 23 human chromosomes are far “lumpier” and “stickier”.

While it is easy to imagine 23 pairs splitting evenly into 2 sets of 23 chromosomes, as the ancestral trail is followed, from a genetic rather than a fractional viewpoint, it is easy to imagine that a great great grandchild might have 50% of the great great grandfather’s chromosomal material, while only 12% of the great great grandmother’s chromosomal material, and the other percentages being provided by the other great great grand parents!

1 offspring has 2 parents, 4 grandparents, 8 great grandparents and 16 great great grandparents. And while Royal lineages dutifully apply percentages of 1/16 (or 6.25%) to each Great Great Grandparent, by the luck of the draw, 25% of one of these g-g-grandparents may have survived 3 generations of mating! - - with the remaining 75% being split in uneven amounts, chunkily apportioned amongst the other ancestral peers:

G-G-Grantparent-01 = 25%
G-G-Grantparent-02 = 6.25%
G-G-Grantparent-03 = 0%
G-G-Grantparent-04 = 0%
G-G-Grantparent-05 = 18.75%
G-G-Grantparent-06 = 6.25%
G-G-Grantparent-07 = 0%
G-G-Grantparent-08 = 0%
G-G-Grantparent-09 = 12.5%
G-G-Grantparent-10 = 6.25%
G-G-Grantparent-11 = 0%
G-G-Grantparent-12 = 12.5%
G-G-Grantparent-13 = 0%
G-G-Grantparent-14 = 6.25%
G-G-Grantparent-15 = 0%
G-G-Grantparent-16 = 6.25%

YOU = 100%

As you can see, “genealogies” are much more democratic. All the Great Great Grands are awarded a 6.25% share of any Great Great Grandchildren. But Chromosomes and Genetics pay no mind to family lineages and equal shares.

One of my kids asked to submit a DNA sample to ancestory site. I get so many mtDNA hits - sometimes 5 a day - that I erase them. mtDNA could go all the way back to Eve, Lucy, whomever.

Age of man is like the age of a person. If I showed you a photo taken every 5 years, you could see a progression. baby- infant- child - teen . . . . But if I showed you a photo taken every year you would be hard-pressed to know where infant stopped and baby started. Change is continuous.

Mike is interested. Me, no much. I was born in NYC. Moved to Seattle in 1962. Mike found a bunch of relatives in Oregon and Alaska that I didn’t know existed. We had more old pictures of their family branch and we didn’t know they who they were. We all met in Portland couple of years ago and traded copies of everything. Been no contact since. Anyway, paying to submit the DNA served a purpose.

I hope everyone is clear with the concise distinction offered by @Swamidass !

Because “genealogy” is a pre-science discipline … they’ve been doing royal genealogies from before the Roman Republic … a genealogy is purely a schematic representation of one person’s parents, and their parents, and their parents, and so forth.

Whether the “spiritual concept” being represented as “bloodline” or the family “genius” … or “male vigor” or what have you … ancestry could be modeled on the simple exponents of “2” … where each generation was twice as big as the generation that came after it.

Genetic ancestors is the new reality … where pairs of chromosomes get halved into 23 chromosomes… and then the lottery begins !!!

If we knew exactly how many active genes there were, we could talk about percentages of genes that you pass on to subsequent generations … and survive into each new generation …

Without knowing how many genes there really are, we can just look at the chromosomes, and assume (for the moment) that no pieces of one chromosome gets switched out with a piece of another chromosome!

Each generation is a coin toss… and by the fluke of the odds… one (or more!) of your chromosomes might make it through 10 generations in a row… .or you could lose the genetic lottery to your descendants in just a few generations!

Very interesting. But I will look for what others say. I enjoy the opportunity to get input and hear from others.

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Thank you @Swamidass for the clarification. So are you proposing the importance of this distinction is that this leaves room for Adam as the genealogical ancestor of all current humans? Thus Adam can be the father of all humanity?

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With the caveat that “humanity” is poorly defined in this context, I think you have my point.

Now, i do understand that many think this is unnecessary theologically. Maybe they are right or not. That is not the point. Rather, nothing in mainstream science tells us that a recent genealogical Adam is not possible.

What I mean is, how do we scientifically define the group of people who (according to Scripture) are supposed to descend from Adam? Does it include Neandertals? Denisovans? Homo sapiens 100,000 years ago? We just do not know, and cannot just assume that it the “mankind” of Scripture = “homo sapiens” in science. Until we define this group, we cannot really determine who “everybody” is.

It does not depend on the reproductive isolation in any way that we can measure.

  1. The small amounts of migration needed to produce a recent genealogical ancestor leave no trace in genomes. They are unobservable.
  2. It is implausible to assert with confidence that the !kung and aboriginal Australians never mixed with everyone else over the last 100,000 years based archeology or any other science. Perhaps they didn’t, but that seems very unlikely.
  3. The fact that we see no genetic evidence of mixing yet, does not tell us anything, because of #1.

So the exact date of the most recent genealogical ancestor of all of us is not observable. But if we assert the very reasonable hypothesis that there was small amounts of mixing over time, then it appears the most recent genealogical ancestor would be less than 10,000 years ago.

So it is incorrect to think that these observations undermine a recent genealogical Adam. They do not.

We probably do agree, but I’m trying to be precise here and give a more limited account of what science does and does not say. I think it is not precise to say that science has ruled out a recent historical Adam. That is not accurate, even if theologically one might think a recent historical Adam is not needed.

This is interesting to think about. I appreciate the food for thought on this.

My initial reaction at this point is that this would have a very niche appeal. YECs will have difficulty entertaining this at all, as their view generally entails Adam as the first and only human, period (before Eve came along). I don’t see them being OK with people living before and alongside Adam (before he had offspring).

And for less literal people such as myself I can’t help but think this feels very ad hoc. It seems that all we get from this is Adam being a common ancestor in some literal sense. But not even the full literal sense that the literal folks are concerned about, which seems peg Adam as sole physical source of humanity (no peers save Eve, nor ancestors).

So I think I am tracking with you about what you’re saying about science not proving a recent genealogical Adam impossible. I’m just not sure this is an Adam anyone is concerned with. He’s neither the “literal” Adam nor the figurative Adam.


There are many people concerned with this. This is the hinge point for most old earth creationists, especially Presbyterians. Jack Collin’s work here should make that 100% clear.

Their problem is not that Theistic Evolutionists take Genesis non-literally. That is just fine by them. Their problem is that they feel Paul is being revised (Romans 5:12). That is where they draw the line.

This is perhaps one of the most commonly raised objections to evolution on theological grounds, and is in the belief statements of countless Christian organizations. For example, read this from Ratio Christi…

We believe in the ex-nihilo special creation of the entire space-time universe, as described in the biblical creation record, and in the direct creation of many diverse biological categories. We also believe in the historicity of the biblical record, including the special creation of Adam and Eve as the literal progenitors of all people, the literal fall and resultant divine curse on the creation.(to footnote)

Footnote: We recognize that the issue of origins is one of the most contentious and most debated of our times. Ratio Christi does not take a position on the age of the earth and acknowledges that this is a good debate to have within Christian circles and allows for those of “young earth” and “old earth” viewpoints to freely and without fear of reprisal graciously express their views. Like the rest of the Bible, Genesis is to be interpreted in a historical grammatical sense, but we acknowledge that even this criterion has led to debates of the exact time frames and sequence of origins. However, the paradigm of scientific naturalism is false and Ratio Christi is committed to showing the shortcomings of this view. We specifically deny “theistic evolution,” yet realize that this is a position that must be vigorously debated in order to show the weaknesses in both the scientific and theological evidence for macro-evolution.

If you talk to them they will say that they reject theistic evolution because it denies “special creation of Adam and Eve as the literal progenitors of all people”. However, as I have shown, this is false. Nothing evolution denies this.

Particularly strange about this debate, is that most theistic evolutionist do not know this. That is a problem. They can reject evolution if they want, but this is a really bad reason to do so. We should uniformly be telling them that nothing in evolution speaks against Paul’s view of Adam.

Do you think they would be OK with progenators in only a genealogical sense? I get the impression that the special creation folks mean special as in first and only, and ancestor in every sense. Would they find Adam in this genealogical sense compelling? Sin entered the world through this Adam? What about Adam’s peers and their descendants, before their tree faded? There was Adam’s sin line, and a bunch of other lines, doing life together, but there was this hidden genealogical thread in the background the whole time? I see what you mean about presenting it as an option, but I wonder if they would also see it as an ad hoc option as well. This seems harder to swallow than a figurative Adam, but of course that is coming from my own point of view already.