Questions about Universal Ancestry


(Peaceful Science) #1

@Jay313 thanks for posting your questions about these estimates. Your confusion here is probably very common, but your effort to closely read the paper helps everyone.

Except there are now. There are now. My estimates are pear reviewed.

They do not explicitly model these changes. Moreover, the discuss exactly what it is that incerases wait times:

  1. Unrealistically low amounts of migration.
  2. Very remote islands (which are only colonized within (about) 3,000 years.
  3. Population size. There is 8 billion alive now, but 5 kya there are just 18 million. 10kya there are just 2 million.

Yes, but that will most likely overestimate the time to UGA. Several types of migration are not accounted for in their model. This one of the big critiques advanced, that they were too conservative.

The variance of the IAP is very high. The variance of the nearly IAP is much much lower. So 15 kya is not what the range for the nearly IAP is.

This calculation is not valid on the high end of the range, because the variance of nearly IAP is much lower than the variance of IAP. Moreover, for a couple in Mesopotamia, the IAP is not really relevant. Only the nearly IAP is relevant, because that is a nearly ideal position. Taking into account the population boom of the agricultural revolution that spreads across the globe from here about 10 kya to 8 kya ago, we just expect that Adam was ancestor of everyone when civilization begins. As knowledge of agriculture spreads, so would his ancestors.

Note, the Rhodes paper does not at all consider the population boom of the agricultural revolution at all, which caused a massive amount of global migration. They do not consider any population level migration at all, which would reduce the estimates dramatically.

I did give ranges (see figures). I also erred often towards more conservative estimates. The goal was to give a likely estimate (but also conservative) given what we know now. I also discuss how those estimates could be improved.

This is only applicable if, for example, Easter Island and Hawaii needs to be colonized. For the time ranges we consider in theology, that makes universal ancestry much easier.


I will point out too that this only matters if you must place Adam 6 kya. Most people who want to preserve the genealogies are not trying to do this. They just want Adam within 10 kya and in an agricultural setting. In that context, there is just no difficulty at all. It would be difficult to imagine how they would not be ancestors of all without positing genealogically isolated populations (which are unobservable).


(Andrew M. Wolfe) #2

Lucky! I’ve only ever been reviewed by peaches and lemons!

(Sorry, I couldn’t resist the pun… :slight_smile: )


(Peaceful Science) #3

I’m not even gonna fix the typo. This pear shall be preserved.

MOD EDIT: :pear: :pear: :pear:


#4

Lettuce pray…


(Jon Garvey) #5

We haven’t yet sorted out all the details on the Genial Adam hypothesis, it’s true.


(Peaceful Science) #6

However I never place Adam with MRUGA. I place instead with a vanilla UGA. We expect they arise everywhere, are often in couples, and there is much higher certainty in estimates about them.

Think about it, if Adam was monogamous and a UGA then for a fact Eve was too. That is just by basic logic. Your objection here is not correct.


(Peaceful Science) #7

Even in the case of Kahn or Charlemagne this is not a problem. Because at least some of their wives are also UGAs too. So then that would be a paired couple. (this is also contingent on them leaving far enough in the past that they are UGAs)

Regarding your second question. That gets to the heart of the confusion. You are trying to transfer your instincts about genetics to genealogy that does not work, and will confuse you every time.

The difference is that m-MRCA and y-MRCA are singular. UGA (do not confuse this with MRUGA) are plentiful and every where. Even MRUGA is not singular but arises simultaneously everywhere. There is no reason, however, to think Adam and Eve must be MOST RECENT, so UGA is just fine.

This figure is helpful…read it in detail and more of this will make sense…

Genealogical ancestry is not genetic ancestry. Illustrating the story in the text, we show a cartooned pedigree, a genealogy, from past (top) to present (bottom). Squares and circles denote men and women, respectively, with lines indicating parentage. Red and blue individuals are those in the genetic lineages to a single ancestor, Mito-Eve and Y-Adam, respectively. In contrast, every individual with a black border is a common genealogical ancestor of all those in recorded history (grey box). The Scriptural Adam and Eve (the black box and square) are created from the dust and a rib less than 10,000 years ago, have no parents, are in the Garden of Eden (black box), and are genealogical ancestors of everyone in history. This story is entirely consistent with the genetic data.


(Peaceful Science) #8

We are not talking about MRCA or MRUGA. We are talking about UGA, which is what many people believe is taught in scripture. There is no claim about MRCA or MRUGA, but there is a claim (some people think) about UGA.

It is critical to understand the form of this argument they are making. They are arguing for a very difficult to believe conclusions, so they built the simulation with a whole range of barriers against recent UGA to (1) make it match the theory closer, (2) head off criticism that making the simulation more accurate would increase time to UGA (in fact it woudl decrease time), and (3) test the dependence on several variables. They find…

  1. The only important variable is migration levels, nothing else they tweaked with had a strong effect.
  2. Several features they did not model are all expected to decrease time to UGA.
  3. IAP has high variance (so they cannot really find strong relationships to variables here), but MRUGA has lower variance, and nearly IAP has lowest variance. We care most about nearly IAP (and I explain why in the paper)

Now regarding the migration (and other details), they intentionally used a model designed to increase the time to UGA, so their final conclusion would be most strong.

  1. Ony move per person per lifetime. No offspring before move.
  2. Lifespans are high, just as you noted (which increases time to UGA), and has the effect of reducing migration (see #1)
  3. Migration (except when demanded) was as individuals, no populations), which dramatically decreases intermixing.
  4. Unrealistic high limits to migration between continents (e.g. only about 100 individuals / generation between europe and asia) so simulation would match their theoretical analysis, and to support their argument that more realistic migration would continue to support their conclusion (making UGAs more recent).
  5. Ignoring known large scale migrations and trade routes (e.g. the Silk Road)
  6. Assuming all couples are monogamous (unless absolutely required not to do so). So prostitution, infidelity, polygamy is all ignored, which would all dramatically reduce time to UGA (but also be much harder to model).
  7. Ignored outbreeding (anti-incest taboo) cultural push entirely.
  8. Used very low levels of migration, and it is only in even lower unrealistically low migration that MRUGA increases.
  9. It ignored the effects of large scale population interactions like refugees and war which has an effect of totally mixing populations over long ranges.
  10. It ignored entirely modern transportation like global travel in airplanes. (@Chris_Falter, does this help with your question?)

So each of these simplifications pushes the UGA estimate farther back in time. That is why this result has stood the test of time (13 years now). A more realistic simulation is possible, but because they biased their simulation so heavily against recent UGAs, a more realistic simulation is expected to reduced time to UGA. That is why no one has even attempted to challenge their results, and this is accepted by population geneticists.

Whatever skepticism you may have, I am certain they have faced more from more trained people. Getting a paper like this into Nature is no joke. It is very difficult.


(Jay Johnson) #9

You failed to understand my questions, but that’s okay.


(Peaceful Science) #10

Help me understand the question then? I want to make sense of it for you.

UGA’s do not require divine intervention.


(George Brooks) #11

@T_aquaticus

Is this you just being difficult? None of the criteria we are explicitly worried about has to do with “genetic contributions” … it is principally about “genealogical contributions” - - which are much less technical, and easier to track.

And from what I’ve seen of the Federal Headship discussions… it seems the phrase “Federal Headship” to be a virtual synonym with “Divinely Created Universal Genealogical Source”!


#12

Isn’t “multiple UGA’s” a contradiction in terms?

As to the UGA being a couple, I will look into it and work through the concepts.[quote=“Swamidass, post:7, topic:37071”]
The Scriptural Adam and Eve (the black box and square) are created from the dust and a rib less than 10,000 years ago, have no parents, are in the Garden of Eden (black box), and are genealogical ancestors of everyone in history.
[/quote]

How can they be the genealogical ancestors of everyone in history? Perhaps you misspoke?

First, they can’t be the ancestors of generations that existed before them. Second, they wouldn’t become UGA’s until well after they had their children. If I was reading Jay’s review of some of the references, the UGA’s of modern population didn’t become UGA’s until very recently meaning that there were still lineages in the past that were not directly tied to the modern UGA.

And I will repeat my the caveat that I often use. I could be completely wrong about this and am open to any correction.


#13

Is this just you being overly sensitive?


(Peaceful Science) #14

Not at all. Have you had a chance to read the preprint yet? That will help make sense of it. You are scientist too, so you will enjoy reading the references. It is really interesting body of work I am tapping into here.

Everyone in “recorded” history in this case. “Everyone” is totally ambiguous term, so is “human.” Admittedly, this is a bit ambiguous in its wording. It is also the wording used in the literature to refer to “all those alive today.”

Put a more precise way, when recorded history begins about 6 kya, everyone is a descendent of UGAs alive 10 kya.

Alternatively, we could also say an Adam 6 kya might be the ancestor of everyone mentioned in Scripture after Genesis 11 (with a few exceptions like, say, Melchizedek if want it so), and also would be the UGA of all Homo sapiens across the globe by AD 1. This is, admittedly, pushing things to the limit (except for the fact this is a conservative estimate). It is more as an illustration than a serious proposal.

That is about correct. Those other lines, by definition, are not what I mean when I say “everyone.” Also none of them appear to be in recorded history. Put a more precise way, when recorded history begins about 6 kya, everyone is a descendent of UGAs alive 10 kya.

You are, but it isn’t your fault. This is a really subtle issue. We have a tendency to translate “ancestry” into “genetic ancestry” with all its entailments. This just misleads intuitions entirely.


(Peaceful Science) #15

They are actually nearly opposite in discourse, though potentially the same as you recognized here. @Jon_Garvey can comment.

The representative model of headship was proposed because UGA seemed impossible. Now, in theological discourse, “headship” and “representative” are often used interchangeably. But this is an error. As you have noticed, genealogical ancestry is another way Adam could be the “head” of the human race. It need not be by representation. It is possible @LorenHaarsma might comment.

Though I am not a theologian, I think genealogical headship is much more plausible than global representative headship. We cannot even have that conversation though, till we separate representative from headship, and this will take some time.


(Christy Hemphill) #16

How so? Christ’s federal headship over the church, to which Adam’s federal headship is a parallel, has nothing to do with ancestry. It’s a purely spiritual concept. So is the concept of Gentiles being “grafted in” to the Jewish family of God, despite no “ancestry” with Abraham.


(Peaceful Science) #17

Yes I know. Except, we also all also genealogical descendents of Abraham.

The issue, which @LorenHaarsma points out in his book, is that Adam as representative has precedence and coherence when we think about a “tribe” of people in a localized place. Especially if this is a single group that chose to be together, they bear consequences for the leader they chose.

However, this is not the situation we see in a representative Adam model. Here, people are spread across the entire globe. It is not clear how or why God would choose to hold people in the America’s immediately responsible for the actions of Adam in the Middle East. Because those in America are certainly not locked in a social exchange or common community with Adam, it does not makes sense to they would bear guilt for his actions. There has not yet been a good explanation of that put forward, at least as I understand it. Though @Jon_Garvey and @LorenHaarsma can jump in of course.

A more plausible approach is @JohnWalton and @tremperlongman’s cultural pollution model. However, at least some theologians, and myself too, find its interaction with Christology to be inadequate. I do not feel it gives adequate explanation of why Jesus is subject too all the temptations we are, but was able to resist them. It also looses the traditional importance of the Virgin Birth in explaining this resistance to traditional sin. Maybe it is correct, or part of the story, but there seems to be some large holes in the theory.

I do agree no one has yet put forward how this can make more sense in genealogical transmission, but I have seen a very good proposal that is currently unpublished. Give that time. Aside from the traditional emphasis on a genealogical transmission, there is more coherence to this that avoids the problems of “cultural pollution” and “representative”.

I think it is correct, nonetheless, to consider these all different types of headship models, with variations on transmission of headship. They are not all equivalent, however, in their coherence.


(Christy Hemphill) #18

How is this problem solved by ancestry? How is it less problematic for God to hold people responsible for ancestors their people have no knowledge of or connection to than “leaders” their people have no knowledge or connection to? You don’t choose your distant ancestors on the other side of the globe either.


(Jon Garvey) #19

It’s difficult discussing any federal headship model in what is the most abnormally individualistic culture the world’s ever produced. The idea of corporate responsibility doesn’t sit comfortably with us ever - and yet we still recognise it is some way: only yesterday our Prime Minister apologised to people who were prosecuted under laws she and her government had no part in making (centuries ago!) - and they still talk about reparations for the Second World War when most of those involved have died.

Federal headship in Reformed theology was a way of viewing our accountability for Adam’s guilt (including explaining why we die) forensically in the context of a broadly literalistic understanding of Adam as the first man.

I know good people who retain the same view of accountability for an Adam representing (unelected!) an already existing, rather than a future, race. “Horizontal” accountability, rather than “vertical”, you might say. Representatives don’t need to be blood relatives.

Yet on the face of it, as Joshua says, that seems a rather diffuse model of human solidarity compared to being descended from Adam. And it really doesn’t answer the question of the transmission of the sinful nature. However, as I suggested, it’s hard to know for sure if God shares our opinions on representative democracy (including the very recent idea that if unless you vote for someone, they don’t represent you).

The examples I mentioned in modern politics are quasi-genealogical: decisions made by previous generations bind ours (eg the US constitution or ancient laws) as “the descendants” - and yet they also bind immigrants into a nation - but not people in other lands. We still recognise the “rightness” of that, so it seems to me there is still a strong instinct of family/tribal solidarity for which the genealogical Adam hypothesis makes sense. It may have been my great grandfather who confiscated Old Masters for the Nazi party, but if they’re hanging on my wall, I’m guilty too.


(Kathryn Applegate) #20

Hi there @Swamidass, I confess I haven’t read this entire thread, but I perked up at this discussion of federal headship. Federal headship, as far as I can tell (not being a theologian), is by definition headship by representation. I don’t know the full history of headship theology, but most of the people in my own community, who embrace covenant theology, wouldn’t doubt UGA because they are YECs who think we are of course directly related to Adam. So federal headship is not a modern innovation to deal with problems raised by evolution.

@Christy is right in saying federal headship is a theological concept. That isn’t to say it settles whether or not the Adam you have proposed did or didn’t exist. It seems to me, though, that genealogy is overshadowed in importance by the biblical notion of adoption.

We are not welcomed into God’s family because of our ancestral relationship to Jesus (which nobody has, since he had no children). Our relationship to Christ–who, it should be noted, is called in Scripture our “elder brother”–is co-heir (8:17). So we are not related by blood but we have all the same rights as if we were.

Working backward from NT to OT, it seems clear that Adam is our representative first and foremost, and is perhaps (but may be only incidentally?) a relative genealogically speaking. Genealogy would only seem to matter if our sin nature was biologically passed down (a la Augustine), but it need not necessarily be, as you have already pointed out.

In any case, please forgive me if I’m treading over ground you’ve covered lots of times elsewhere! It’s an interesting discussion for sure.