Technical note relevant to this conversation is this paper I came across. It is a much more easy to follow approach than MSMC and others. It is based on Bayesian analysis and machine learning, and has some advantages over the other approaches we have discussed.
The underlying data is LD blocks and allele frequency spectrum (as @glipsnort used). One of the nice things about this approach is that it should (I think) run much more quickly, and allow for direct testing of the bottleneck hypothesis (with modification). I also trust the confidence intervals on this method. Among its disadvantages, it does not actually reconstruct the phylogenetic trees. So it is going to be a bit more opaque in other sense.
The recent posts are not talking about bottlenecks of Homo sapiens, but bottlenecks of our ancestors as a whole.
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That is not correct.
As we have discussed. @DennisVenema clarified that he meant Homo sapiens exclusively, not our ancestors a whole. As you quoted me summarizing him:
Homo sapiens specifically do not dip down to a single couple in 300 kya to the confidence we have in heliocentrism.
Without belaboring the point, that claim seems to be unsubstantiated by evidence. We already know that Homo sapiens dip down to zero, so positing they dip down to two is certainly not a problem. Perhaps Homo sapiens do arise as a single couple, subsequently interbreed with other hominids, thereby giving rise to us.
Agreed, our ancestors who were either properly homo sapien or so very close enough to be genetically reproductively compatible. To me, that pretty much feels like a taxonomical distinction without a meaningful difference but agreed all the same.
Now after Richard tells you that he doesnât see the evidence falsifying the âhypothesisâ that our ancestors dipped down to 2 within the past 300K years, you can ask him if it falsifies the âhypothesisâ that our ancestors dipped down to 2 within the past 10K years.
This distinction doesnât look meaningful in the context of the original debate. If homo sapiens had non-homo sapiens ancestors, how can homo sapiens have emerged solely from a bottleneck of two homo sapiens who had no ancestors? I just donât get how youâre going to make the evidence fit YEC.
Saying the population of homo sapiens dips to two is not the same as saying homo sapiens emerged from a single pair. This is why I view the âpopulation of homo sapiens may have dipped down to twoâ argument as extremely misleading. It looks a lot like a bait and switch.
What Josh is saying is that our ancestors if you go back far enough wouldnât be classified as homo sapien any longer. Theyâd be other species (e.g., homo erectus). That would be your population of zero. Of course gradual changes wouldnât ever result in a pre-homo sapien to homo sapien transition where you say, ah hah! Here are the first two humans. The differences at that point in time would be negligible and largely invisible within a generation. As Dennis has noted previously, if you go back far enough taxonomical distinctions break down. What I think Josh is proposing is that our ancestors which would have constituted breeding populations preserving our genetic diversity could not have dipped to 2 within the past 300K years. If only that what we classify as homo sapien could have dipped down to 2 while other âhomoâ classed species so very genetically and behaviorally similar to ours maintained larger population sizes. Like I said, a taxonomical difference without a meaningful distinction.
Yes I understand that. My question remains; how does this fit the idea of homo sapiens emerging exclusively from a pair of homo sapiens with no ancestors?
Yes I understand he is saying that. As I said, I donât see how itâs relevant to the idea that homo sapiens emerged from a population of two people with no ancestors. Additionally, I see the emphasis on âhomo sapiens could have dipped down to two individualsâ as a loaded statement intended to imply that homo sapiens could have emerged from a single couple without ancestors.
I donât believe that is how Josh is using the bottleneck language. Apparently thereâs some fraction of a percent of Christians who feel if you could argue that itâs possible there were two homo sapien (on a technicality) survivors to regrow a population of humans within the larger breeding population of human ancestors so very similar genetically and behaviorally, that you could rescue some sliver of the Adam & Eve story. If you were so inclined.
Iâd contrast this with Richardâs approach. Which appears to be one of extended agnosticism on anything that might contradict the YEC narrative, and who crafts his statements in such a way to be 100% compatible with that âdoctrine.â
What is written here is an honest gesture of good will coming from a curious scientist in the Church. I have also been clear that I do not think the YEC data fits the data, and am happy to explain why, and have explained why several times. The fact that I am glad to acknowledge when the data does fit their model does not make me suspect. It makes me honest.
Yes, but I am not talking about that. Iâm talking about the fact that you want to âfind a way for YEC time scale to work with the evidence without abusingâ indicates that your motivation for involvement in this subject is apologetic and theological, rather than scientific.
Not true @Jonathan_Burke. Seriously, that is not a valid read. It honestly comes off as an ad hominem. If you have a problme with the data Iâve presented, feel free to point it out.
Iâm honestly curious how you are going to square my statements about the evidence with being a YEC apologists. That is totally absurd. Remember, Iâve said:
It is not ad hominem. An ad hominem argument takes the form âPerson X has character flaws Y, therefore their argument is falseâ. I have not said anything like that. I have not said that any of your arguments about the data are false, and I have certainly not said âSwamidass has character flaws X, therefore his arguments about the genetic data are wrongâ. Nor have I said âSwamidass is a YEC apologist, therefore his arguments about the genetic data are wrongâ. Nor have I called you a YEC apologist, which is a phrase implying you believe in YEC (which you obviously donât).
As you know, I have not contested the data you have presented.
I have not said you are a YEC apologist. I have said that your statement that you think it would be great to âfind a way for YEC time scale to work with the evidence without abusingâ indicates that your motivation for involvement in this subject is apologetic and theological, rather than scientific. If your only interest in the topic was scientific, then I donât understand the need for such a statement. I donât see why you would say it would be great to âfind a way for YEC time scale to work with the evidence without abusingâ if that is not actually something you would like to see happen.
I should not need to remind you that this entire topic was raised by Dr Buggs specifically as a Christian apologetic for Christians who believe in a literal Adam and Eve (as in fact I do). This is the post in question.
âDoes genomic evidence make it scientifically impossible that the human lineage could have ever passed through a population bottleneck of just two individuals? This is a question I am asked semi-frequently by religious friends.â
âThe issue is this. Believers in Abrahamic religions who accept evolution often combine it with belief that all humans have descended from a single couple. Until now, many have assumed that this belief is compatible with evolution and mainstream science.â
âVenema declares that a bottleneck of two is impossible, and this is a fact of comparable scientific certainty to heliocentrism. He gives his Christian readers a stark choice between embracing mainstream science, or sticking with untenable beliefs about an ancestral couple.â
âWhilst this issue may seem trivial to many readers, for large numbers of religious believers in the world, this is a critical issue. Do they really face a binary choice between accepting mainstream science and believing that humans have, at some point in their history, all descended from a single couple?â
Yes I know what youâve said. Youâve said this.
YECs wouldnât have an issue with that, since youâve deliberately said âwithout either miraclesâ. Naturally they would be happy with the idea of fixing the data with miracles. Youâve also said this.
I donât see those as mutually exclusive statements, and clearly you donât believe youâve contradicted yourself either.
It took some digging to find the original quote, but what I gather Josh is getting at is not attacking strawmen. Something I very much agree with as well. Thereâs enough absurdity within the YEC movement that thereâs no need for us to manufacture it. Thatâs why when Dennis and others started talking about Eve as essentially a clone of Adam, my eyes rolled. Virtually all of my family are YEC, and I donât know a single one who would ascribe to that view. Theyâd rather think that God worked some magic genetically to pack in as much diversity as possible into their genomes. Also silly, but letâs talk about the silliness that exists rather than forcing on others that which doesnât.
Josh also points out that if you can get in the habit of avoiding strawmen, your rebuttals of YECâs actual arguments will carry much more weight. Again, I completely agree. He also makes clear the aspect of the YEC timeline heâs interested in is Adam. Not all of creation or all of humanity or human ancestors. If âwhatâs importantâ to the YEC community is an Adam at 6,000 years ago, well if Josh can give them a sliver of a straw to grasp onto on some technicality, and that works for them, then maybe that might open the doors to a few to accept what we know to be scientific fact about the history of our planet and life on it. I personally think thatâs a stretch too far and require, even by YEC standards, too much in the way of mental gymnastics. But thatâs where Joshâs head seems to be at. I do think youâre misunderstanding him on this. He seems to be trying to play the role of âmissionaryâ to the YEC community.
I raised no objection to his statement that strawmen should not be attacked. I fully support him on that point. The quotation I provided was on a completely different subject.
In about ten minutes I found and posted two YEC organizations which discussed the idea that Eve was a clone of Adam. One presented it as one of two possible ways God had created Eve, the other said it was the way God had created Eve. Creation Ministries said this.
âThere is an intriguing possibility that Eve was a clone of Adam. The science of cloning involves taking DNA from an organism and using it to manufacture an almost perfect copy of the original. Here, God is taking a piece of flesh, with cells, organelles, and, importantly, Adamâs DNA, and using it to manufacture a woman. Of course, she could not be a perfect clone, because she was a girl! But what if God had taken Adamâs genome and used it to manufacture Eve? All he would have had to do was to leave out Adamâs Y chromosome and double his X chromosome and, voilĂĄ, instant woman!â
They go on to say this later.
âThere are indications, however, that Eve may not have been a clone.â
But they still say the cloning idea is one of two available possibilities. Meanwhile, another YEC organization says this.
âSince Eve was made from one of Adamâs ribs [Genesis 2:21-22], she would have been a clone of Adam and, had there been any genetic mutation in Adam, this would have been reproduced in Eve and expressed in their offspring.â
So there are definitely YECs who argue this.
I agree in part. Itâs a nice idea which might work in some cases, but the fact is that most of us avoid strawmen when it comes to YECs and it makes not a scrap of difference whatsoever.
Yes he is definitely trying to offer them a sliver of hope, but I donât see that his motivation for helping them believe they are right, is to move them to a position where they accept they are wrong. I really donât see how that is going to work. Weâre talking about people who think that the âsoft tissuesâ found by Schweitzer proves that dinosaurs only died out recently. I cannot see how giving them the impression (wittingly or unwittingly), that their views on Adam and Eve and a 6,000 year old earth are not in conflict with science, is going to help them change their minds.
Consequently I canât see this is as a missionary endeavour. Trying to give them reasons to hold onto their 6,000 year old earth and 6,000 year ago Adam and Eve, isnât going to lead to them abandoning their 6,000 year old earth and 6,000 year ago Adam and Eve, especially when that 6,000 year timeframe is there precisely as their only bulwark against evolution.
[quote=âtallen_1, post:424, topic:37039â]
I do think youâre misunderstanding him on this. He seems to be trying to play the role of âmissionaryâ to the YEC community.[/quote]
I see him as mediator rather than missionary. If he was playing the role of missionary he would be aiming to change their views, not suggesting people come up with concordist interpretations of the evidence which could agree with what YECs believe.
I was providing the background context for Joshâs sympathizing with the YEC community. The quote you lifted out of that context can create the wrong impression.
Also, I donât think what I provided was off topic given you included this in your quote: âAnd that is exactly the hypothesis that YECs and OECs have been working with over the last decade. Anyone who does [not] know this has just not been listening.â To know what Josh is referring to you have to attend to what he was saying about misrepresentations and straw men, which is what I explained. Maybe you didnât mean to include that section in your quote, but there it is.
Anyway, Josh does not appear to be facilitating any sort of hope to the YEC community for their 6K year earth or creation de novo of all living species within that time. Heâs only extending them that hope for a 6K year old Adam. As their greatest theological hold up always seems to go back to Adam.
Certainly they are combined roles. As fellow Christians, I would not see a YEC adherent as in need of a missionary, but there are many in that mindset who have fallen away from Christ due to the dichotomy presented in that culture ( of course, that is another kettle of fish but AIG seems to agree with that loss from what I have read ) and that becomes a place where a missionary field is present.