Adam, Eve and Population Genetics: A Reply to Dr. Richard Buggs (Part 2)


(system) #1

This is a companion discussion topic for the original entry at https://biologos.org/blogs/dennis-venema-letters-to-the-duchess/adam-eve-and-population-genetics-a-reply-to-dr-richard-buggs-part-2

#2

Dennis great job on explaining population genetics to a layman whose last biology course was in high school and we won’t go into exactly how long ago that was.

One comment, the last study you mentioned isn’t identified. Perhaps you could add that to the otherwise excellent article.


(Dennis Venema) #3

Good catch - I guess the URL went missing in either my copy or in the editing. Not sure. Here it is - perhaps @BradKramer can edit it into the post.


(Vincent Torley) #4

Hi Professor Venema,

Great article. As you’re probably aware, Dr. Ann Gauger believes there was a severe bottleneck around two million years ago, with the emergence of Homo erectus, whom she identifies as the first true human being. Is there anything that rules out her ancient severe bottleneck scenario, at present?

By the way, in the second-last paragraph, “Dr. Bugg’s hypothesis” should read “Dr. Buggs’s hypothesis.” Cheers.


(Dennis Venema) #5

I must have missed that one - I did studiously try to avoid getting those possessives wrong - paging @BradKramer for another edit…

At 2 million years ago we don’t have the coverage of methods that we do for ~1MYA and onwards. If @agauger thinks we can read Genesis as set at 2MYA with another species, I don’t think there’s a scientific case that rules that out, at least at present. At that point, in my opinion, we’re so far afield from what Genesis is saying that it seems really ad hoc to me. YMMV.


(Brad Kramer) #6

@DennisVenema @Bill_II Your wish is my command. Should be fixed now.


(Vincent Torley) #7

Hi Professor Venema,

In plain English, what you’re saying is that science can’t rule out an original couple, if they lived more than 1 million years ago. Dr. Gauger will probably welcome that admission.

For my part, I can’t see why a 2-million-year-old Adam and Eve is any more at odds with what Genesis is saying than, say, a 100,000-year-old Adam and Eve.

However, if I were to identify the chief flaw of the ancient Adam and Eve scenario, it would be this: modern human behavior doesn’t appear until 100,000 years ago. Homo erectus may have had foresight (transporting tools over distances of more than 10 kilometers), the ability to control fire (although this is hotly disputed) and even a sense of aesthetics (judging from the elegance of some Acheulean tools), but it almost certainly lacked the capacity for art, religion and science. This means that in some ways it was less human than we are - which means that if we are to believe in Adam and Eve, we have to give up belief in human equality.

It is instructive to compare Homo erectus with modern-day tribes whose lifestyle has been described by some as “primitive.” Members of these tribes have relatively little trouble in adapting to the cognitive demands of civilization, some making the transition in as little as a generation. I doubt very much whether Homo erectus could have done that. And I also doubt whether anyone could have preached the Gospel to Homo erectus.


(Dennis Venema) #8

I guess it depends on how reliable you think PSMC methods are as they approach this time frame. The data looks smooth to me out to around 1.5 MYA or so, plus or minus, but the method loses its power as you go back further and further.

Yes, the main issue is that at 1-2MYA, human (or hominin) behaviour is nothing like what we consider normative for modern humans.

For my part, I think the whole exercise to find an ancient A & E is driven by concordism. I’d rather let Genesis be Genesis on its own terms.

*Note as well that I am not an official BioLogos voice on these matters - this is my own personal opinion, lest anyone be confused. I think approaches that have Adam and Eve within a cultural context that fits Genesis (i.e. around 6-10KYA) are much better ways to go if one is interested in a model that has a historical Adam and Eve.


(Brad Kramer) #9

I think it says a lot about the “historical Adam” conversation that some folks are OK with moving noticeably beyond the context of Genesis 2-4 as long as there is an original pair of some sort.


(George Brooks) #10

@DennisVenema

That is a fine article !

I note with some interest these two studies as solid, basic studies of the points in question:

1st Study
"Later pre-HGP papers were in agreement with these early results. For example, this paper looked at allele diversity at the PHDA1 gene, and reports a human effective population size of ~18,000."

2nd Study
"Similarly, studies of allelic diversity at the beta-globin gene [study] found it to indicate an ancestral effective population size of ~11,000, and conclude that “There is no evidence for an exponential expansion out of a bottlenecked founding population, and an effective population size of approximately 10,000 has been maintained.”

Since my brain has evolved to understand math when presented in an Excel spreadsheet (surprisingly rapid evolution I might add), do you think it would be possible to throw some hypothetical numbers into a spreadsheet, and show how the calculations proceed from the raw data to the answer of 10,000 (or 11,000, or whatever the hypothetical numbers generate)?


#11

I agree. It does seem like a weird flip-flop of priorities/first principles for those concerned with a certain “literal” reading of the text. Is an original couple (as sole progenotors of the entire human race) so sacrosanct that all the other (Neolithic) details of the biblical text are simply ornamental? Frankly, I might have more sympathy for the quasi-solipsism of YEC than some odd concordist proposal that puts Adam And Eve that far back in history.


(Brad Kramer) #12

It seems to me that most of the theological energy put behind the “sole progenitor single pair Adam and Eve” concept is being driven by soteriological concerns from the New Testament—mostly in Romans and Corinthians—rather than exegetical concerns about Genesis itself. Whenever I hear about Adam, Paul is not far behind.

Necessary Disclaimer: My view here is my own, there are others in the BioLogos camp who would see it differently.


#13

I am wondering if the driving force is a belief in OEC without evolution. The OEC gets you out beyond 6,000 years but then you need something to safeguard you from the temptation to give in to evolution. A special creation of A&E would do that.

Now, if there was only some book that could describe the OEC position in their own words. Wonder where I could find such a book ? :wink:


#14

Agreed. For those who feel constrained to read Paul that way, I’d suggest @Swamidass’ “Geneological Adam” proposal as a better option—not that I agree or disagree with it, but it seems more plausible among current (semi-) concordist options that could help those who feel compelled to read Paul a specific way (and, no, I’m not trying to restir some recent controversy).


(Jon) #15

To me, the standout feature of this post is the clear evidence that scientists have in fact previously investigated the possibility of the human population passing through an extremely small bottleneck, and their conclusion that a bottleneck of even a few individuals has been ruled out by the available evidence.

The reason why this stands out to me is that Dr Buggs has given the very strong impression that no one has ever made such an investigation before, that no scientists have ever tried to model such a small population, that no scientists have ever concluded that there is evidence ruling out such a tight bottleneck. That is the impression I have received from statements such as this.

In contrast, Dennis has shown that several such studies have been done, and that scientists have in fact made the conclusion that a bottleneck as sharp as the one Dr Buggs is proposing has not occurred in the last 500,000 years.

  • “Also suggested is that the population size has never dropped to a few individuals, even in a single generation”

  • “There is no evidence for an exponential expansion out of a bottlenecked founding population, and an effective population size of approximately 10,000 has been maintained”

  • “On the other hand our results also deny the hypothesis that there was a severe hourglass contraction in the number of our ancestors in the late middle and upper Pleistocene”

  • “Moreover, the ancient genetic history of humans indicates no severe bottleneck during the evolution of humans in the last half million years; otherwise, much of the ancient genetic history would have been lost during a severe bottleneck”

What surprises me is that Dr Buggs has never mentioned these studies, and has in fact given the impression that such studies do not exist.

Regardless of the outcome of the discussion between Dennis and Dr Buggs, the only question I have is this (which I have posed previously to Dr Buggs).

Does your understanding of the data support the idea of an Adam and Eve who had no ancestors at all (neither human nor pre-human), as the universal progenitors of every human who has ever lived, with no humans descending from any parallel humans or pre-humans, approximately 6,000 years ago?


(Tim) #16

Dennis,

Can you clarify the difference between these coalescent methods and the allele frequency analysis Steve was performing? Thanks!


(Curtis Henderson) #17

I see what you did there! :wink:[quote=“vjtorley, post:7, topic:37338”]
This means that in some ways it was less human than we are - which means that if we are to believe in Adam and Eve, we have to give up belief in human equality.
[/quote]

I’m assuming what you mean here is that you consider the Homo erectus of 100 kya as unequal to the Homo sapiens of today. To take this a step further, are you suggesting that Adam and Eve must have been H. sapiens, and thus more recent?


(Vincent Torley) #18

Hi Brad,

I agree with your comment about St. Paul’s theology underlying the endeavor to defend monogenism (or monogenesis, as some prefer to call it). I realize that if you were arguing from Genesis alone, you could make a good case that Adam is meant to represent Everyman. But if Jesus Christ is the second Adam, as St. Paul argues, and if Adam is not a single individual, then why should Jesus Christ be? The symmetry of the metaphor appears to require that if the second Adam is a historical person (as Christians believe), the first Adam should be too.

We seem to be in agreement that if there was a historical Adam, he must have lived over a million years ago. Dr. Ann Gauger identifies him with the 2-million-year-old progenitor of Homo erectus, while Dr. Dennis Bonnette suggests that he was the first specimen of Heidelberg man, around one million years ago. That saves Adam, but as I’ve argued in a recent post on The Skeptical Zone, the point at which modern human behavior appeared seems to be around 100,000 years ago, not one or two million. Homo erectus and Heidelberg man possessed a kind of rationality, but probably not language or symbolism. See here for more: http://theskepticalzone.com/wp/envs-shockingly-bad-argument-that-humans-are-products-of-intelligent-design/ . So if Adam was the first Homo erectus or Heidelberg man, he was a lot dimmer than we are. It is hard to see him as our equal.

I have also been prepared to entertain the notion that maybe Adam was the head of a tribe, whose members agreed to let him decide the spiritual fate of the human race. If so, then perhaps a bottleneck of a few hundred individuals would be theologically acceptable. But if the Fall took place within the last million years, then from what Professor Venema has written, it seems that the lowest we can go is a few thousand individuals - which is far too many for a single tribe.

Other authors (such as Kenneth Kemp) have proposed the notion of ensouled humans interbreeding with virtually identical hominins, thereby accounting for the large bottleneck. But the notion that two individuals might be genetic conspecifics, with one possessing a rational soul and the other lacking it, makes no theological sense. And what would happen to their offspring? It all sounds very ad hoc to me.

Finally, some have proposed a Neolithic Adam. That certainly harmonizes with the Biblical chronology and the data in Genesis 4, but the idea that humans were not aware of God until a few thousand years ago makes no sense. Surely Cro-Magnon man worshiped something. And if he did, then why should a choice made by one of his Neolithic descendants have any negative implications for the human race as a whole?

So it seems we have a bad set of options. Which is the least bad? Search me.


(George Brooks) #19

@vjtorley

This seems to be an opportunity to clutch straws. One could argue that you have a Jesus as a sacrifice for all historical humanity.

I don’t see people alleging that Jesus has to be a hermaphrodite for his powers of atonement to extend to females.!

Or, even more peculiar, the idea that we should have two messiah’s - - one for each gender. After all, God created first one gender, then the next. Would that logically entail creating a male messiah and a female one?


(Phil) #20

This argument strikes me as entirely contrived. If Jesus is the second Adam, which I believe he is, then it is in a symbolic or metaphorical sense. He presumably does not have Adam’s genes, Adam’s form (unless Adam was a non-descript Jewish guy), or Adam’s faults, but Jesus assumes his place in a symbolic sense. Therefore, the argument as to physicality is mute.