The time scale of the bottleneck?

What gaps?

It all depends on how exactly you define “similarity”. After the rather long discussion on the Human Chimp Genome Similarity thread 95%, using the definition in that thread, appears to be a reasonable estimation.

I refer to “God of the gaps” type arguments. This is seen in the way you hide your belief in what science does not know and make the sucker’s bet that future development will not prove you wrong, even though current evaluations of the evidence does not agree with what you prefer to believe.

Indeed! For some people surface superficialities like shape, color and sex are the most important things for their identity and thus they make these things of theirs the measure of humanity. The surface differences from chimpanzees are obvious so it is hardly surprising that the DNA is different, something must account for that. But are these the important differences. Are the important differences the genetic ones at all, or is there something more important, something more essential to our humanity? I think so!

If pigs could talk and complain about their treatment would you still be arguing percentages of DNA? Is the fact that they don’t look like us really all that important? Is the fact that their DNA is different so important either? I reject a world which lives by such an attitude. After all, what percentage similarity is enough? At one time people in this country might have compared the DNA of black people and made that their justification for slavery, and at other times and place they would have done the same for women.

Thus I utterly reject the idea that our humanity is defined by a genome. We are human because of something entirely different. It is the human mind and abstract capable language from which it is built which really makes us what we are, and things like shape, color, and sex are irrelevant. Furthermore I would argue that if you compare the information carrying capabilities of DNA and human language, the latter is demonstrably superior.

Your agreements are irrelevant to me. The scientific measure is 99% or if you want greater precision 98.8%. But if you want to shift the question to importance of similarities and difference, well then you now know I think the important ones are not found in DNA at all.

Previously I think the number was 97% then they found that the portions which were different from the DNA in different species of chimpanzees were not the same, and that accounts for the additional 1.8%, for the point is that 98.8% of our DNA is found in one species of chimpanzee or the other.

You need to read the thread. The “agreement” was between several experts in the field with copious references to published papers. Do you have any papers that reference the 98.8% number?

BTW, no mention was made of defining humanity by the genome. The discussion was on common ancestry.

I agree with this. I believe something happened about 70,000 years ago, the great leap forward, that made homo sapiens into modern humans.

To be sure there are a lot of difficulties in making the comparison. For example, chimpanzees as well as some other apes and monkeys have 24 pairs of chromosomes while we only have 23 pairs. This is just one way in which we have to overlook less important differences to zero in on the differences which matter. The end result has been a determination by the scientific community is that when you boil this down to the differences which matter you get a 98.8 percent similarity.

But sure if you go hunting for excuses to inflate the differences then you can no doubt come up with bigger numbers for the differences. I am certainly not interested in the results of some internet discussion which has decided to split the difference between the inflated numbers and the determination by the scientific community.

The discussion is entitled “the time scale of the bottleneck” to which I gave 3 reasons why I would not agree with connecting Adam and Eve (and thus humanity) with the genetic bottleneck in our ancestry in Southern Africa 100,000 to 200,000 years ago. Thus arose the question as to what are the real differences between human beings and animals.

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This is a nice article highlighting how the types of difference we see among human genomes follow the same pattern of the types of differences we see between humans and chimpanzees - demonstrating that the same mechanisms are responsible for the difference:


What did Richard Buggs really say?
At post 35 he said;

In his last post he said;

So Richard Buggs has not accepted 95% as reasonable. It is still outside his upper bound estimate.

… , the human genome has between 84.4% and 93.4% one-to-one orthology …
Mean = 88.95%
Upper Quartile = 91.15%

I am able to accept that God is perfectly capable of using evolution to create life on Earth.
But I don’t think he did.

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George what am I missing? There were some migration bottlenecks of ~500 people or so within the pas 50,000 years but there is no evidence of any serious Homo sapien bottleneck, not even going back to common ancestors with chimpanzees. I’m not sure what we are discussing here. Are you talking about Y-chromosome Adam which here is a summary of some different methods:

@aarceng Brother Chris , I appreciate your congenial way of discussing things. It’s always good to have iron sharpening iron.


In the course of the conversation Richard did change his opinion on the % of similarity. So I noticed 2 things about his final comment way down at post 120. He no longer mentions a lower bound on his range estimate and admits that 95% is possible (otherwise it wouldn’t count as a prediction) but not yet an “established fact”. So perhaps instead of reasonable I should have said possible. Not much difference in my mind.

If I might ask, what do you think is the significance of a similarity of 93.4% or greater with the chimp?

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It seems to me that all the evidence including migration, Y-chromosomal Adam and mitochondrial Eve all agrees with a long bottleneck in the human population in southern Africa between 100,000 and 200,000 years ago, which could have gone as low as 2000 people. There is additional evidence of a migratory bottleneck from a migration across the Bering strait which could have been as few as 70 people. This, of course, rejects the Toba catastrophe hypothesis which the evidence hasn’t supported. This also seems to be the origin of modern homo-sapiens species which agrees with the logical link between low population and high genetic drift.

It seems to me the chart given for different estimates of the time for Y chromosomal Adams seems to agree rather well with this. The estimates place this as no more recent that 100,000 years ago and a few push this back to as far as 250,000 years ago. And it should be noted that older estimates do not logically disagree with the long bottleneck hypothesis 100,000 to 200,000 years ago.

What do you mean by ‘long bottleneck?’ I haven’t seen any papers with a bottleneck of 2,000 some people besides regional bottlenecks involving migration but not for the human genome as a whole. Could you point me to something you are looking at?

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This is an almost hopeless muddle. Neither Y-chr Adam nor mito Eve has anything to do with bottlenecks. I have personally never heard of a “long bottleneck” in southern Africa, though I do know of some old-ish theorizing about the species riding out a rough stretch by eating a lot of shellfish in Africa. Not my area, but I think that’s pretty speculative. No matter what, you should be wary of any discussion of bottlenecking that uses Y-Adam or mito-Eve as evidence. That’s a basic error.

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That’s funny… since a google search brings these up quite easily.

Incorrect. At the most you can say this is weak evidence. It is just that there is a higher probability of having these during a genetic bottleneck than at other times. I don’t think it is a coincidence that the estimates of these two fall in the same time frame.

I think there is a bit of over-reacting involved in this subject. The idea that ANY of this supports the idea of humanity coming from two people is absurd. But that doesn’t mean we have lean over backwards to ignore any evidence of a genetic bottleneck at all. Like I mentioned, it is just plain logic that you are going to expect the greatest genetic change in small populations on the brink of extinction and we have the homo-sapiens species appearing in just the right time frame to fit all of this. Sure it is speculative and I am not a biologist who has to be oh-so careful not to go too far from what can be proven without a doubt. I am just a dilettante willing to place my bets where the probability points best.

Yes, I read that article. And this is a part of the body of evidence I am talking about. I am also talking about all the migration and linguistic evidence that tells a story of human migration from southern Africa to the rest of the world.

Compared to my own area of physics, all of this stuff looks pretty speculative to me. Not that physics doesn’t have a few areas ripe with speculation.

I found this old review article discussing the long-neck bottle(neck) idea. It predates large scale genomics. I don’t know whether it is still considered plausible or not but I suspect we have much more data by which to judge such ideas. Your claims, which I was responding to, seem to be a melange of different ideas, of varying quality (the ~2000 individuals thing is not a specific part of the long-neck idea, as near as I can tell).

You are making an error. There is no necessary connection between a common ancestor and a bottleneck. None. Pick any common ancestor you want; we could use you and me. Identify that common ancestor. Then postulate a bottleneck? Why? It’s an error, and it creates a lot of confusion.


I didn’t say there was a necessary connection. Your soapbox is not my problem. What I said is that there is a higher probability of having a Y-chromosomal Adam and mitochondrial Eve during a genetic bottleneck than at other times. This is just simple logic. Do I really have to demonstrate this to you, because I have math skills to do so if you insist.

This is a discussion of a very different genetic bottleneck, long before the appearance of modern homo-sapiens. That there are more such periods in our evolutionary history is something that I would expect.

I must have missed it. Can you point me to the post where he said that? Until then I will assume that his estimate of between 84.4% and 93.4% still applies.

Robert W. Carter and Matthew Powell have done a study using a “population modelling program designed to examine changes in allele frequency within ‘biblical’ populations.” A special program had to be written because other programs can’t handle the low population numbers, stochastic modelling, and level of detail required for such an analysis. They conclude that “skeptical claims that biblical models are excluded by population genetics are unwarranted.”

The genetic effects of the population bottleneck associated with the Genesis Flood

Really? The models by experts in population genetics can’t handle small populations, stochastic modeling and any level of detail… but for those who don’t even publish in real scientific journals they can do it?!?

Genetic fallacy.