Michael Denton’s new book is out, Evolution: Still A Theory In Crisis.
Denton’s stance is for structuralism and against functionalism, especially as functionalism appears in it’s current form as the modern synthesis or neo-Darwinism (the cumulative selection of small adaptive changes).
Denton argues for the reality of the types, that “there are unique taxon-defining novelties not led up to gradually from some antecedent form” and that the lack of intermediates undermines the Darwinian account of evolution. He also argues that a great deal of organic order appears to be non-adaptive, including “a great number of the taxa-defining Bauplans,” and that this also undermines the Darwinian account of evolution. Evo-devo is also showing us that “Darwinian selection is not the only or even the main factor that determined the shape and main branches of the great tree of life.”
These arguments are first set forth in Chapters 3 through 5 of the book and then defended throughout the subsequent chapters.
Denton provides a list of some of the Type-Defining Homologs:
The Pentadactyl Limb
The Feather
The Insect Body Plan
The Flower
The Amniotic Membrane
It is not just the major taxa which are characterized by unique defining homologs or novelties:
Centipedes
Beetles
Ants
Butterflies
Even individual species are often defined by unique novelties (autapomorphies in cladist terminology).
To head off a lot of irrelevant objections and nonsense from people who can’t be bothered to read the book, Denton accepts common descent and doesn’t appeal to “goddidit” as a better explanation.
- If types exist, what does that mean for Darwinian evolution?
- Does the existence of non-adaptive order undermine Darwinism?
- Does anyone think neo-Darwinism is even relevant to modern evolutionary theory?
Are you and your siblings as separated from each other as from anyone else?
Someone needs to call the guys doing paternity tests and explain them Sal has debunked the technique
stcordova,
What you say is true, if and only if there is no selection…
I used to work on the yeast S. cerevisiae. A buddy who worked on S. pombe was very fond of pointing out that S. cerevisiae and S. pombe are as far apart as either is from man, and further that cell cycle control in S. pombe was much more like that in metazoans than cell cycle control in S. cerevisiae. It was a little bit annoying, frankly, but he was right. They may both be unicellular yeasts, but they are VERY different.
These days, he goes by “Sir Paul”, I believe.
😉
LOL. My undergraduate degree is in biochemistry, my graduate degree is in molecular biology.
I wouldn’t call myself a biologist either; I prefer the term “DNA Jock”.
DNA_Jock,
Or LGT …
What does “separated from each other” mean? Has Sal counted the molecular differences between two lineages of fish separated from each other by the same amount of time? Are there such lineages?
http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.0050101
Sal, I’m confused by this entire line of reasoning. Yeast share more recent common ancestry with each other than any of them do with other non-yeast organisms. Given this, why are you surprised that one yeast citochrome oxidase is more similar to another yeast citochrome oxidase than either is to a mammalian citochrome oxidase?
Of these two different views, I believe Dave Carlson’s view is the more recent, more correct one.
It does seem that critics tend to think of divergence nodes as an everything-at-once kind of thing – more like pollarding than a typical iteratively branching tree.
These kinds of criticism of molecular phylogeny are of the “you’d-think-someone-would-have-noticed” variety. I mean, to labour the point, an entire field could conceivably be wrong, but … you’d think someone would have noticed.
Joe Felsenstein,
True. Paul was exaggerating somewhat.
His point, and mine, was that just because they are both unicellular yeasts doesn’t mean that they aren’t wildly different from each other. To a creationist, they are still just “yeasts”, whereas for a scientist, it’s fruitful to study both.
I’m sure there will be surprises ahead, but I don’t think Sal is going to be happy with future findings in molecular evolution.
Does Denton even mention this?
Indeed. That’s a fair point which is even demonstrated in the Dayhoff chart that Sal linked to. The yeast citochromes may be more similar to each other than to any non-yeast citochromes, but the intra-yeast divergence (for this protein and this subset of yeast, at least) is greater than, say, the intra-vertebrate divergence.
The same is true of William Dembski’s arguments, such as his invocation of the No Free Lunch theorem. A century of theoretical population genetics, and no one noticed that natural selection would not work? In a field that contained R.A. Fisher, Sewall Wright, and J.B.S. Haldane? You had to get up very early in the morning to outthink them.
One thing that I suggest is worth looking at is the INTRA-species variation.
But based on the INTRA-species variation we can at least tell when the bottleneck was that make them each S. Cerevisiae cytchrome so similar to another S. Cerevisiae cytchrome.
Yeast can regenerate in about 80 minutes. Let’s be generous and assume 1 day generation time. In 5 million years S. cerevisiae will have gone through 1,825,000,000 generations. That would be more generations than the tertapods since titaalik or whatever creature was the ancestor of tetrapods 375 mya. If the sequence divergence in S. cerevisiae vs another S. cerevisiae is next to nothing, doesn’t that look a little incongruous?
What about when candida yeast separated from saccharomyces yeast? The divergence is only 25 in the dayhoff diagram. Contrast the insects vs. tetrapods in the dayhoff diagram that’s in the 40’s. Considering animals came about 600 mya and have slower generation time than yeasts, why are they more divergent (like insects vs. tetrapods) than candida yeast vs. baker’s yeast (Saccharomyces cerevisiae)? One will say, but yeast are close relatives of each other.
To which I respond, ok if that’s the case, how far back in time did candida and baker’s yeast share a common ancestor? A million years ago? How about baker’s yeast vs. baker’s yeast. If the divergence is even smaller (baker’s yeast vs baker’s yeast), are we talking a recent common ancestor of all baker’s yeasts in the ball park of a few hundred thousand years?
Does anybody even try to estimate what time frame a bottleneck must have happened to create such low INTRA-group and INTRA-species divergences like say between candida and saccharomyces or baker’s yeast (in asia) vs. baker’s yeast (in south america)? Whatever, something looks incongruous to me.
Yes, lets assume this is the case. So when did the split happen in terms of millions of years ago? Candida and Baker’s yeast are only 25 away from each other.
But what might be more poignant is if we assume the evolutionary timelines are correct. What would we expect as far as the time frame for all the common ancestors of each of the yeast species based on the INTRA-species divergence not the inter-species divergence. The incongruity might show itself more obviously then.
That’s sort of why I was looking at the E. Coli aaRS. It was mostly conserved. Ok, so when was did the E. Coli ancestor go through a bottle neck to make all E. Coli’s be so conserved in aaRS?
The same question could be asked of every yeast species. How far back in time did the bottle neck happen for each yeast species?
When the ancestors of Candida and Baker’s yeast split, the Baker’s yeast clocks should still be ticking between the individuals of the Baker’s yeast family. If the baker’s yeasts have almost all identical genes or proteins for a phylogenetic marker (like cytochrome C protein or gene), then it indicates a recent bottle neck for today’s baker’s yeast long after the candida and baker’s yeast split. If we see that bottle neck pattern everywhere, that would seem really odd. I suspect that to be the case.
The dayhoff diagram suggested it to me, but a more rigorous apporach would be to just look at the INTRA-species variation and hypothesize when the bottlenecks must have happened for each species.
stcordova,
Sal, if you are interested in looking up estimated divergence times between different organisms, one resource you can use is the Time Tree of Life.
Using this resource, the median of published divergence times between Candida and Baker’s yeast is 315 million years (http://www.timetree.org/search/pairwise/candida/Saccharomyces%20cerevisiae), while the median divergence time between insects and tetrapods (using Drosophila and dog as the exemplars) is about 900 million years (http://www.timetree.org/search/pairwise/9612/7215).
Note that there is a lot of variability in these estimates, but it is quite clear that the split between arthropods and tetrapods predates the split between the two yeast lineages in question. Therefore, the divergence estimate of this single protein that you find incongruous is perfectly reasonable.
Thank you for the reference link! Many thanks. I didn’t know about it.
But the yeast generation time is hundreds of times more rapid than arthropods and tetrapods. For this “incongruity” to be perfectly reasonable, we have to make the unreasonable assumption that there is a lineage specific trans-generational tick rate! This point was not lost on Hoyle nor Denton nor Behe nor others.
Ok, Hoyle’s population genetics left a lot to be desired, but he was right about the mechanical difficulties of protein phylogenies, one of them being the necessary differences in tick rates in each lineage (like yeast lineage vs. animal lineasge) in order for the molecular clocks to have reasonable synchronization!
As I suggested, the better way to settle this is just looking at individuals within a recongized species and using the accpeted molecular clock rates, estimate how far back the bottle neck for each species must have occurred.
I’m raising this issue here, because if I think it’s a promising area of research I will suggest it to the Creationist/ID underground who are biology saavy. It’s tedious research but not difficult to learn how to do now that the NIH NCBI has so many experimental records of sequencing experiments in specific geographical locations.
We don’t need even necessarily to have a stable definition of species, we need only identify taxonomically restricted features that define a group like the E. Coli’s 20% conserved core.
A tentative scientific prediction by yours truly: INTRA-species variation will indicate relatively recent bottle necks for most species.
I believe that because I think the patterns of diversity in the genes and proteins is by common design and relatively recent specially creation, not through common descent. I believe the INTRA-species variation studies will point to common design and relatively recent special creation.
And once all the data are in, I predict that you will decide they indicate common design and special creation NO MATTER WHAT THOSE DATA ARE!!
Let’s see whose prediction proves out.
OK, I’m going out on a limb:
INTRA-species variation will indicate relatively recent bottle necks for most species.
Looks like a nice beer bet. Actually I prefer desert wines. I particularly like this one from Michigan where there are grapes and lots of snow and ice:
http://www.blackstarfarms.com/harvest-to-bottle-with-a-capella-ice-wine/
Define bottleneck and define recent.
You can’t really have a bottleneck in a single celled organism. Not likely, anyway, outside a laboratory.
Speaking of which, Lenski’s populations vary from 200 to 800 mutations. Actual data. So you wouldn’t want to set your watch by a molecular clock.
Are you going to include plants? Invertebrates?
Exactly! So why are the E. Coli aaRS genes 98-99.9% conserved. 🙂
At least for animals we have the concept of MCRA (most recent common ancestor). The MCRA for human females I believe is mitochondrial human eve. We have doggie and cattle mtDNA Eve as well. They are indicated at 10,000 years back, human Eve 6,500. But even accepting mainstream numbers, what if we do similar stuff for all animals we can do this for. What if we find all the mtDNA MRCAs are only at most a million years back for each species. Won’t that strike you as a tad odd if we are dealing with animals that migrated tens of millions of years ago?
Is there an mtDNA equis (horses and zebras). How about mtDNA mouse or mtDNA rat?
Good idea! It’s not going to be me, but others if they are willing.
I will make a bioinformatics presentation some day to the creationist community. I think the presentation can be public domain since there is nothing secret about the idea. The only sensitive thing is who is going to get involved and how we are going to tablulate the data.
There are a few hundred if not a few thousand creationists matriculating through biology college curriculums in the USA each year and there are even more with computational backgrounds, and it won’t take a lot of training to teach them how to do some searching of literature and genetic databases. It would be a good learning exercise for everyone involved no matter who is doing it and no matter what the final outcome of the research yields. The project will help in increasing science literacy, imho, whatever the results of the study.
stcordova,
Sal, much of what you’re saying here is so elliptical as to be incomprehensible. But let me throw a few words in your direction. mtEve is not the MRCA of all female humans; it’s the MRCA of all human mitochondrial genomes. Even so, 6500 years for mtEve is a bizarre estimate, and I would like to know where you got it. Now you can use genetic data to estimate past population sizes, but when you try that there is no bottleneck detectable, and a minimum population size of about 50,000 for the past 100,000 years or more. Genetic similarity within species need not be due to bottlenecks; drift within populations results in limited genetic diversity, and an equilibrium similarity given enough time and a constant population size.
And your ideas about cytochrome c evolution make at least two invalid assumptions: that protein evolution is neutral and that a yeast generation is equivalent to a human generation in terms of expected mutation rate. Protein evolution is clearly more clocklike than neutral evolution under that model would be, and it clearly is much slower in general than neutral evolution. A yeast generation is a single cell generation, while a human generation is many cell generations; if I recall about 30 in the female line and averaging many more in the male line. Further, the rate of nearly neutral evolution (probably a better model of protein evolution, though still not a good one) depends inversely on population size, and yeasts have much larger population sizes than humans.
stcordova,
I am by no means an expert on molecular clock analyses (and I would be happy to hear from anybody who knows more about these questions than I do), but here are a few points to consider:
– keep in mind that the Dayhoff chart shows divergence in a single protein (and a mitchondrial one at that!), and this data will not even capture the majority of neutral DNA changes that don’t result in amino acid changes. In addition, it has been known for decades that different proteins will “tick” at different rates. Because of this, I think it’s fairly dangerous to draw major conclusions from this single data point.
– In addition, there are plenty of other factors besides generation time that will influence the rate at which a particular sequence will accumulate mutations. These include (but are of course not limited to) effective population size and changes in selective regime. I don’t know what the Ne of yeast is, but I think it’s safe to assume that it’s massively larger than the Ne of any animal. Therefore purifying selection will be more efficient in yeast, and this will, on average, decrease the fraction of mutations that behave neutrally and are fixed by drift compared to other species with much lower Ne. I also think it’s reasonably safe to conclude that there have been a bewildering number of adaptive changes in the lineages that arose from the common ancestor of tetrapods and arthropods. Have there been more mutations fixed by positive selection since the common ancestor of dogs and Drosophila than since the common ancestor of Candida and Saccharomyces? I don’t know for sure, but I wouldn’t be surprised if that were the case.
– Finally, while yeast may have much smaller generation times than either insects or tetrapods, they also experience many fewer meiotic cell divisions per generation, which will impact the overall mutation rate in a lineage. Here’s an important quote I came across from Lynch et al. 2008 (http://www.pnas.org/content/105/27/9272.full) while trying to find information on yeast mutation rates:
Edit: And I see that John Harshman made many of the same points as I did, only faster and more succinctly. 🙂
6500 years is easily explained by a miracle.
Perhaps the same miracle that enabled people in the Americas avoid the Flood.
John Harshman,
Thank you for the helpful criticisms. I was in error on the MCRA and mtDNA Eve, thanks for pointing it out.
Sal
So, unsurprisingly, there already exists a substantial body of evidence in support of common descent of all these lineages, along with a substantial body of evidence of both intra and inter-species variation. All of which is consistent with not only common descent, but with truly ancient common ancestors.
From which Sal has, as predicted, concluded common design and recent creation. Does anyone seriously expect that more evidence reinforcing existing evidence will alter his foregone conclusion?
Regarding the conservation of the aaRS gene among all E. coli forms even though E. Coli total genome is only 20% conserved between strains, I think a bottle neck is indicated. I suspect the 20% core is indicative of the MCRA E. Coli’s descendants losing genes. I don’t know about the impact of MGE (mobile genetic elements) that are causing gene exchange between E. Coli and whatever else is out there….
If one assumes selection is monkeying with the molecular clock, that it’s preventing aaRS evolution, then it casts doubt on why there should be inter-species differences at all in the aaRS gene. So the problem of E. Coli conservation doesn’t go away easily.
Additionally, now that we have cheap sequencers, we might be able to see if there real time divergence happening in E. Coli strains world wide…..
How can we get aaRS or cytochrome C or whatever conservation for such a staggeringly large population as all the E. Coli on the planet? It would seem to me there is an MCRA E. Coli genotype that unifies all E. Coli.
There is a further complication as far as the migration of E. Coli or other microbes that are part of micro biomes of creatures. The NIH has a huge micro biome project, and we only know a little.
But just to get an idea of what would be needed to get this descendants of a new MCRA E. Coli on the scene and for it to appear in so many diverse microbiomes, I point to this article someone in jest somewhat in seriousness:
So how would this new MCRA E. Coli or the other microbial species transmit to each host to then become global? It doesn’t seem like a trivial issue.
Btw, the micro biome in a human has more cells than the number of human cells
in the human — goes to show how much smaller microbial cells are compared to Eukaryotic multicellular cells like human cells.
Sal has learned stuff. He could take over the department of arguments creationists should not use at AIG.
I can’t think of any other creationist who has made concessions or learned anything.
There’s on concession that most of us have to make in life. I figured it out somewhere between age 16 and 20.
That although i was smarter that most of the kids in my school, i was not as smart as most of the scientists who are famous. And definitely not smart enough to find glaring errors in the scientific consensus.
Every now and then I find a typo in a book. I find stupid things in press releases. Whoopee.
Agreed. I’m thus putting on the table some ideas of how to settle the issue. You and John Harshman and Joe Felsenstein have given me some pointers. I’m not a specialist either, but I know of specialists and I may try to prod them to get interested in the project, if only to assign it to their students. There are a few creationists who are teaching micro biology. I’m hoping they might see it as something they can assign to their undergrads. The assigment would be something like this:
1. pick a gene on a species
2. find all strains of that species that have been placed in respectable gene banks
3. estimate the sequence divergence between the strains
4. estimate the time of the MCRA under various clock rates
5. find out if there is a published clock rate for that gene for interspecies variation
6. calculate the MCRA using that clock rate
7. submit the results to the creationist knowledge base
Don’t we have all that fancy software inspired by Joe Felsenstein’s work to figure out an MCRA or whatever we call it.
As I said, the peculiar situation is that although Joe is an evolutionist, he has so many admirers in the creationist community!
Maybe I haven’t been paying as close attention as you have. I’ve seen Sal make a great many concessions — and when the topic cycles around again, he’s back where he was before, having either ignored or forgotten all concessions, and we do it all over again. But maybe you’re right, because each time he has cherry picked and misinterpreted some different detail.
In 150 years of biological research, there’s clearly a wealth of details which can be plucked out of context and forced to fit Sal’s doctrine. One can’t help but wonder why he goes to the effort to dig them up — he knows he isn’t going to change scientific history or knowledge, and isn’t going to convert from YEC to sane.
I don’t think I’m allowed to say what I think.
You’re welcome, but that’s hardly all you were in error on. I hope you paid attention to the rest of the reply too. Also, you consistently misspell “MRCA” for some reason.
I think what you’re trying to grope toward is the coalescent. This is not the same thing as the MRCA, and it doesn’t have the significance you attribute to it.
I will keep them in mind, but in light of where we might find some agreement, isn’t it hypothetically possible to estimate an MRCA for a group of related individuals? Isn’t that what all those phylogenetic methods are supposed to help us do? If phylogenetic methods supposedly build the tree of life, it surely should work even better for small branches — like strains or races of a known species.
If we have all the known strains of E. Coli, granted it is unicellular, isn’t it possible to infer an MRCA? It would seem some genes would return one number and then other genes another. That’s Ok, that’s something we have to deal with.
I think the MRCA will be relatively recent for most species in our gene banks now and in the future.
So wherever I’m wrong or right in my speculations, we have at least a method in principle to investigate if my hypothesis is correct. My hypothesis is:
For unicellular species, the bottle neck may even imply only one survivor that became the MRCA.
My hypothesis will be falsified if we see most species having wide INTRA-species divergence and the MRCA consistently far back as when the major radiations.
Example: we have sharks lots of “living fossils”. Do their DNA samples indicate the MRCA is recent or hundreds of millions of years back. We may not have a necessary sample of individuals. But we can start building the infrastructure to process the data points as they come in.
From Wiki:
That’s all true, but the coalescent event of a particular set of gene copies (i.e., the MRCA of that sample of gene copies) often does not occur at same time as the MRCA of the organisms that contain those gene copies. This is a major headache when you want to know the phylogeny of the species, but it’s just how evolution works.
I have two degrees in biology, make a living in a chemistry laboratory, and wouldn’t call myself either.
You should know that the coalescent represents the age of the MRCA of one particular linkage group in one particular sample of individuals. There is no need for or implication of a bottleneck, and in fact the most common coalescent methods assume a constant population size.
stcordova,
I’m afraid that your conjectures show a great many misconceptions. Most phylogenetic methods assume that the data form a tree. Interbreeding populations do not form a tree but a complex network. And even bacteria have sex. Nor does the MRCA of a population, if in fact there is one single sequence, have anything necessarily to do with the origin of the species. I’m not even sure you know what you mean by “bottleneck”, or why you should expect a coalescent to have anything to do with one.
By “bottleneck” Sal is referring to the single pair of each species preserved on Noah’s Ark. And since this encompasses ALL species, we should expect to find a recent bottleneck in every instance. Now all he has to do is convince himself he’s found evidence of them. Which is a slam dunk, since he’s already convinced.
That’s why I here so you guys can set me straight.
But if there is inter species gene exchange, doesn’t this cause a problem for everyone — creationist and evolutionist. It doesn’t stop you guys from asserting phylogenies even if you know you guys have a chance of being wrong. There is often a debate to what extent a similarity is HGT vs common descent.
But the HGT invocation has it’s own set of problems. Let’s say we have a population of 5 pentillion E. Coli in the guts of some animals somewhat geographically distributed.
Are you going to use HGT as an explanation for 98-99.9% INTRA-species conservation of a gene? What if the conservation is 99.9%. For some species your concerns seem warranted, for some, it strikes me as mostly irrelevant.
The most reasonable phylogenetic explanation that individuals of the same species are 99.9% identical in DNA regions is they proceeded from an MRCA and the similarity is due to common descent not HGT.
For those who advocate the molecular clock, the problems you raise (like bacterial sex) also affect their hypotheses, not just mine.
Agreed. But if we found most species to proceed from their respective MRCAs, I would find that interesting for its own sake outside the creation evolution controversy.
You’re the one who introduced the word coalsecent not me. You said,
I have a set of baker’s yeast strains reported on the NIH NCBI databases, I want to estimate when they had an MRCA. Is that plausible or not? What conditions makes the quest for an MRCA plausible?
One barrier to your being “set straight” is that you think you understand more than you do. The various mistaken assumptions make it hard to understand you, and the words in your sentences tend not to fit together into clear ideas. I beseech you, in the bowels of Christ, have a little less confidence that you know what you’re talking about.
What, for example, do you mean by “MRCA”? Are you referring to a single individual, a single sequence, or a single population? Do you understand that a given set of homologous sequences (ignoring recombination) will have a single sequence as their common ancestor even without a population bottleneck? This means that your search for a “recent” (whatever that means) MRCA has little to do with the phenomena you are apparently trying to investigate. As for the MRCA of an entire population, whether there is one would depend on whether there is any recombination or frequency-dependent selection going on. If either of these is happening, there probably isn’t an individual MRCA, just an ancestral population.
Hair-tearing stuff!
stcordova,
And if the ‘tree’ assumption is wrong, this can be teased out of the data. For example, there’s a virogene that occurs in Old World monkeys, and numerous cat species but not ‘big cats’. It’s in figure 10.24 in Futuyma’s Evolutionary Biology (3rd Ed.), and Li & Graur’s Fundamentals of Molecular Evolution.
This virogene sticks out like a sore thumb. If you based your phylogeny solely on it, you’d conclude that most cats (but not the big ones) were descendants of the primate line. Since every other gene and morphological feature contradicts this hypothesis, a more reasonable conclusion is that there was a transfer from primates to cats after the divergence of leopard, cheetah and lion, but before the divergence of the smaller cat species (including our domestic moggy).
The ‘tree’ assumption for this virogene still holds good in smaller cats and all the monkeys. The point at which it fails gives us the point at which an HGT event almost certainly occurred – a single instance of viral transfer from one individual to another, requiring no ‘bottleneck’. So violations of the tree assumption are themselves informative, but could not be identified without it.
And of course you can do more – you can type the virogene’s own relationship to retroelements. By assuming that descent of DNA/RNA sequence should logically form a tree pattern (noting that vertical descent through mitosis is not the only kind of tree that can be produced at gene level).
If I didn’t before, I do now thanks to you. 🙂
But seriously, if we take two individuals out of a population. We see some strong similarities in them, we can infer they had an MRCA without assuming there was a bottleneck that caused it, it just means they were related a few or so generations back — example, the Abraham modal haplotype, or stuff we just find in the Hap Map databases, etc.
But isn’t there a point when we feel we’ve gotten a representative sample of a population, say a global population, and the the MRCA doesn’t go back any farther the more data points we add, that we reasonably conclude we have the MRCA. It then remains to hypothesize the explanation.
If we allow the idea of “bottle” neck to include allopatric splitting off, then it would seem reasonable to assume at some point the patterns of diversity in the present day population point to only one ancestor.
In the case of Eve, the way I read the literature is mtDNA Eve is the mother of all females — that the MRCA of mtDNA is also the MRCA of all females. Is that a true statement or not?
Is there not a point when the MRCA of a gene set is indeed the MRCA of the sample of a population and at some point it becomes reasonable for the MRCA of a gene set to be considered the MRCA of the species in question?
Thanks for your responses and criticisms and corrections. They were very informative.
The most recent common ancestor of all females and of all males, actually. But …
I’m not sure this question is meaningful. As we go back in time, while the maternal ancestry of all of us is narrowing down to Mitochondrial Eve, the ancestry of each other part of the genome is also narrowing down to other ancestors. In the absence of a ridiculously small bottleneck, these are mostly going to be different people. So yes, there is a mitochondrial Eve, but there is also a Hemoglobin Beta Bob, and a Cytochrome C Samantha, and a Little-piece-of-junk-DNA Larry. And at least 30,000 of them. They didn’t all live at the same time. In fact for nuclear DNA they are mostly deeper in time (say 500,000 to 1,000,000 years ago). There wasn’t a moment when all these MRCAs were around simultaneously. There is no reason to think that Mitochondrial Eve ever met Y-chromosome Adam.
As always so incredibly informative.
And if I can indulge a question which I hope has a simple answer that relates to this comment:
Yes, now it makes sense, and also like the sickle cell trait MRCA or Tay Sach’s MRCA that exist but aren’t fixed in the population. Thank you.
But, with unicellular creatures, is that as much of a problem? Despite the fact of HGT between asexual creatures, are there situations we can, with some caveats, infer when the MRCA of a species existed.
Does your book on Phylogeny cover these sort of questions.
Thank you again.
It may seem reasonable to you, but it isn’t in fact reasonable. It’s true for any one small bit of DNA, but not at all for the whole genome.
Not. The MRCA of mtDNA is also the MRCA of all females in the strictly female lineage. But all females have male ancestors as well as female ancestors whose lineages pass through at least one male. It’s unlikely that anyone has any nuclear DNA from the mtDNA ancestor.
That would be true in a strictly clonal population in the absence of any frequency-dependent selection. In any recombining or sexually reproducing population (or if there were some mechanism, such as the afore-mentioned frequency-dependent selection, maintaining genetic diversity), there would be no such individual.
The answer is “yes”, but note that this MRCA would likely have been one individual in a large population, not any sort of bottleneck, and the time of that individual would have been no special time in the life of the species. And we aren’t actually talking about the MRCA of a species, per se, just of all the individuals in the current population of that species. If we allow for directional selection, by the way, this MRCA could be much more recent than drift would imply; look up “selective sweep”.
Is! mtDNA Eve is the MRCA of all of the human species, male and female.
Which, means now I have to un-correct myself and say, you were wrong and I was right in the first place. I mistakenly accepted your “correction” earlier where you said:
I accepted your statement, but then I re-asked the question and then Joe pointed out:
I thank God for Joe! What he says also agrees with the gospel according to Wiki (which really is less authoritative than Joe, but anyway):
So I have to uncorrect myself because I accepted what you said as true and I should not have:
So, I take part of that back. Still thank you for your criticisms as the exchange helps me think things through a little more, but I’m think it’s apparent now, I was right in the first place, and I had no need of correction on that point.
Sorry to disagree, but at this point I’d be telling something wrong to others if I agreed with this statement by you:
Moving on….
My mom is the most recent common female ancestor of me and my siblings. It doesn’t imply any of us have all her DNA. I never meant to suggest MRCA for sexually reproducing species necessarily implies the nuclear DNA is solely from the matrilienal MRCA.
But for asexually reproducing species (some of which have no nucleus and hence no nuclear DNA), won’t there be cases where the MRCA of a gene set is the the MRCA of the species? If so, what conditions would be required to make that inference valid?
Thank you nevertheless for reading and responding.