Evolution Requires Reduction in Genetic Diversity

The evidence seems to show that Homo Neanderthal and Homo Sapiens sapiens were isolated for tens if not hundreds of thousands of years yet also shows that the two distinct species could and did interbreed.Is this evidence that isolation alone is not sufficient to prevent interbreeding even when dealing with two or more closely related but separate species?

Indeed it is.
I don't feel it to be a separate spin off issue because it addresses the points made by Faith directly.The questions, I think, to be posed here are:

1. is changing song caused by ecological isolation or is it working on its own (as well)? Is it just the icing on the cake of ecological isolation and/or can it act on its own, for instance due to genetic drift or in the same way human languages change over time and slowly losing mutual intelligibility?
2. When reproductive isolation occurs, does this speed up genetic divergence between the two new sister species (due to the loss of genetic flow)?
3. would the fact that postzygotic factors usually play little role in speciation not be explained by the observation that it's mostly and merely the result of ecological isolation? In that scenario hybrid incompatibility is the genetic and phenotype result of ecological isolation and not to be deemed a separate factor after all and different pollinators, different breeding patterns/timing, different mating habits (bird songs/displays) are just its manifestation within the reproductive realm.

Maybe some good starters.Edited by Denisova, : No reason given.

ifthespacewereimportantthenwewouldseeselectionagainstindeleventsthatwouldbedetectableatthesame timethatisaratherrudimentaryfunctionakintovestigialorgansortheactualjunkinyourkitchenNow what would happen when we remove punctuation?
I think it would cause a text to be illegible and prone to causing communication errors. Especially when a whole book was written and edited without.Are indels only affecting spacer DNA then?
No they don't.
When an indel affects the spacer DNA, causing troubles in transciption of the adjacent genes, would this bring deleterious effects and thus would it be trigger selective effects?
Most likely it would. One of the interesting outcomes of the ENCODE project was the observation that at least 70% of the human DNA actually is transcribed. It made them draw the flawed conclusion that these 70% of human DNA also must be "functional". That's wrong. But STILL the fact stands that 70% of our DNA is transcribed. And transcription costs energy. Especially when it happens all the time in all of the organism's cells.Moreover, most proteins are, often extremely, redundant. For instance, cytochrome C consists of a chain of about 100-104 amino acids. As a consequence, it has been shown that the human cytochrome C protein works in yeast (a unicellular organism) that had its own native cytochrome C gene deleted, even though yeast cytochrome C differs from human cytochrome C over 40% of the protein. Furthermore, extensive genetic analysis of cytochrome C has demonstrated that the majority of the protein sequence is unnecessary for its function in vivo. Only about a third of the 100 amino acids in cytochrome C are necessary to specify its function. Most of the amino acids in cytochrome C are therefore also hypervariable.Now this applies to all proteins and it means that when, for instance, cytochrome C is produced in the cell, at least two-third of the work is just superfluously done. That will cost a lot of energy.As a matter of fact, prokaryote genomes contain much less junk. For some reason they manage to get lost of their genetic junk. Maybe they need so. Because one of the major differences between prokaryotes and eukaryotes is the latter have a far better net energy balance due to their chloroplasts and mitochondria. They can afford to sustain a lot of genetic junk and protein redundancy.And a lot of redundancy and junk eukaryotes drag around with them indeed. The human genome size is 3.2 Gb large and already known for its junk. But what about the plant Fritillaria assyrica (130 Gb) or Paris japonica (150 Gb). Or the marbled lungfish (Protopterus aethiopicus, 130 Gb). To name a few. You hardly can argue these species are more complex than humans, to account for their larger genomes. It seems that the genome size of many eukaryotes does not particularly appear relate to genetic complexity. See The Complexity of Eukaryotic Genomes - The Cell - NCBI Bookshelf, particularly Figure 4.1, Genome size - The Cell - NCBI Bookshelf.Which raises the question why eukaryotes do not get rid of this junk and redundancy. Because after all, it costs energy and resources. When such phenomena are that persistent, there must be an evolutionary advantage for it. Otherwise all that junk would have gotten rid of by selection, like in prokaryotes.That would be an interesting thing to elaborate on i think.Edited by Denisova, : No reason given.

I think you also have to account for the time factor.
The first "true Neanderthals" appeared between 200,000 and 250,000 years ago in Eurasia and most probably descended from Homo Heidelbergensis. They never were in Africa.Homo sapiens' cradle is Africa and only some 60,000 years ago one of its branches for the first time migrated out of the continent. It also has been estimated that the last Neanderthal gene flow into early ancestors of Europeans occurred 47,000—65,000 years BC. That matches the date of first Homo sapiens first migration out of Africa. Comparison with different Neanderthal specimens found the most likely region of interbreeding to be the Middle East. That's indeed the first place you encounter when leaving Africa.Hence it seems that Neanderthals and Sapiens first took their time to diverge in separate regions, only later to meet each other.

Yet still were not just capable of interbreeding but actually did breed together.

Unless you can clarify, I don't see in what way HBD is off-topic. His point that drift, selection and migration are necessary causes of allelic frequency changes was made as a direct counter to your claim that allelic frequencies could change through isolation and nothing else. This paragraph might confuse a lot of people. HBD provided a summary of your position that seems right on to me, but you then accuse him of making it up, and then contradictively conclude that "it's simply what I happened to think."Or did you mean that he's making it up when he says that mutations can add diversity, because if so then I immediately rule that this is self evidently true, almost on the order of 1 plus 1 equals 2, even if only deleterious mutations are considered.Could you please clarify your meaning?

Yes but your initial question was: Which is answered I think: the previous 140,000 years of ecological and geographical isolation before their encounter in the Middle East between the H. sapiens and H. Neanderthal populations apparently did not suffice to establish reproductive isolation.One could argue that 140,000 years represent, evolutionary spoken, a rather short time span.
Furthermore, there is the question whether Neanderthals and Sapiens were separate species altogether. When they were able to interbreed, they weren't according to one of the most important criteria for speciation: reproductive isolation.You may read this article about the issue: Were Neanderthals a different species? - Genetic Literacy Project, where Svante Pbo explains that the male hybrids of Neanderthals and Sapiens were infertile, like mules, and that we owe our Neanderthal genes to hybrid females - which brings David Reich of Harvard Medical School to the conclusion that we and Neanderthals were at the edge of biological compatibility. which subsequently made Fred Spoor conclude This underlines that modern humans and Neanderthals are indeed different species.To my opinion two populations are still belonging to the same species when there is still some gene flow between them - even when only through the maternal line.Edited by Denisova, : No reason given.

So is 140,000 a longer period of time than the 4400 years or so since the claimed Biblical Flood or even the 6000 years or so since the claimed Fall?

Indeed it is but as you may have noticed I am not of the biblical branch pertaining explanations of the natural world. A bit difficult to grasp your point at this moment.

Don't tell me you accept evolution now... But the problem with creationist's view of "microevolution" is that pretty much everything is microevolution. So even if, for example, the order Diptera diverged from a single fly pair on the ark into the more than 240,000 species we have today, that would be "microevolution." - "they are still flies!" So saying you are talking about "microevolution" simply obfuscates what we are really talking about, and that is the formation of distinct, differentiated populations - ie. speciation. But that doesn't mean that they ARE wrong. That is where you need to provide evidence that they are; what you keep doing is repeating your assertion and accusing me of dishonesty. I try REALLY hard to understand what point you are trying to make and address that - if there is misunderstanding it is an honest mistake. Let me sum up what I see as your explanation as to how new species form: A small subset of the population breaks off and moves into a new geographical location. This sub-set of the population has only a portion of the alleles in the original population and because the population size is so small they undergo a period of inbreeding that brings about new genetic combinations. Over time, this sub-population becomes quite distinctive from the original population to the point that it no longer interbreeds with the original population.Is that about right? Show me the evidence of that. Not just re-stating your hypothesis, but provide some data. You missed an important aspect of outbreeding depression. It is more than just "genetic problems caused by two different genotypes coming together." There is an important aspect of those two different genotypes that you appear to have overlooked. Faith, you always seem to be right even when you are wrong. So what does this sentence actually mean? This would be a great time for data. So there is no way a subspecies can give rise to another subspecies? All dog breeds were derived directly from the wolf? Or do you allow a certain number of branching events? This seems to be an extremely bold claim with even very little logical support. So you claim. But it should be clear that I don't uncritically accept the ToE. Just as one example, do you not see Taq and I arguing over the term "junk DNA?" I have been convinced of the ToE by critically studying it and I still think many aspects are controversial - such as gradualism verses punctuated equilibrium, is sympatric speciation possible in natural populations, is "junk DNA" an appropriate term to use. So the claim that I am "so busy swallowing the ToE whole" is a "big fat lie" to use your own words. The funny thing is that your ideas only work in your head; it was the same situation in the geology threads. If you want to show me how things "really" work... show me some data; show me the research that demonstrates how it really works. And you can't claim that the lack of data is due to the fact that no one is looking for the things you claim because you also claim that we are all working with the same data just interpreting it differently. So find some data that has been interpreted "wrong" and show me how it should be interpreted. Part of the problem is that you don't address so many of the points we bring up. I know you are only one person and so it is understandable that you don't have time to address every argument, but it may be helpful to getting this thread back "on track" to go back and address some of them.Your claim is that population splits cause an irreversible depletion in genetic diversity. However, I think it is still unclear what you mean by "genetic diversity." I would ask that you go back and address my Message 459 and carefully consider the questions about genetic diversity that I posed. And don't just tell me what you "think" give some justification (preferably with examples) for you position. Maybe then I won't have to debate with a phantom Faith.HBD

My point is pretty simple. If as the evidence shows modern Homo Sapiens sapiens and Homo Neanderthals were capable of breeding and producing fertile offspring (even if only on the maternal line) then somehow that needs to be incorporated into the Biblical Creation or Biblical Floods explanation. Was Adam the Homo Neanderthals or was Noah the Homo Neanderthals? If the latter then where in the genealogy did the Homo Neanderthals join the family? How can this be consolidated into only 4400 or even 6000 years? Maybe Eve or Noah's wife Naamah (after all she was the sister of a descendant of Cain) was the Homo Neanderthals.How did that mating of Homo Sapiens sapiens and Homo Neanderthals cause a reduction in genetic diversity?Inquiring minds want to know.Biblical Creationism and Biblical Floods genetics is so much fun.

Ah I think I caught up....BTW don't forget Homo Denisova.
Or Homo Floriensis.
Or, for that matter, Homo erectus, who manufactured and applied tools and used fire.Noah's family took in the weirdest of lodgers...Edited by Denisova, : No reason given.

Of course not --- ANY population is inevitably going to develop changes in allele frequency due to genetic drift, it is just more noticeable in small populations.We just know that it is one of many mechanisms that affect evolution of species within habitats. Again, of course we won't --- ANY population is inevitably going to pair recessive alleles through normal mating, it is just more noticeable in small populations. As herebedragons says: founder effect.Any small population without significant selection pressure will see more of the homogenic recessive offspring survive and interbreed than a larger population.We just know that it is one of many mechanisms that affect evolution of species within habitats. That doesn't explain genetic incompatibility. What new combinations? This is the combinations you can have before the split: And that is also the combinations available when reunited -- unless one allele is mutated (D → E in my example).Nor do I see how a new mutated allele can affect genetic compatibility. The possible combinations post mutation are: There are only two new combinations between pop1 and pop2: AE and BE, so -- unless the of the gene is changed, how could there be genetic incompatibility when the populations recombine?What I am trying to do here Faith is draw a line between changes to alleles and changes to gene function. It seems to me that only changes to gene function can cause genetic incompatibility. What I don't see is how shuffling existing alleles changes gene function enough to cause genetic incompatibility.Enjoy

In the latest study they did find some (rare) hybrids between the two northern varieties, so we know that genetic incompatibility is not involved, just shuffling of alleles and some changes to alleles, not to gene function. This of course also means that according to the biological definition of species that trochiloides is in fact all one species. It would seem that this is what is affecting trochiloides as it appears they migrate south to similar locations but spread out in these locations to breed. Is actually just one way that Prezygotic isolation occurs, so I would combine (1) and (2). This would occur via mutations that change the bend sequence\shape of the DNA strand, which would also change the function (protein production) of the gene yes?If that pairing incompatibility were due to a recessive gene, then would not that very same pairing incompatibility prevent that gene to participate in heterozygous mating? The only cases of single mutation speciation that I am aware of involve polyploidy. Indeed. I am reading the first, and note this comment:

quote:

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As first noted by MULLER (1942), all hybrid incompatibilities must be asymmetric. Figure 1 shows that, although B might be incompatible with A, a cannot be incompatible with b. The reason is simple: aabb represents an ancestral step in the divergence of these taxa (i.e., aabb is either the genotype of the common ancestor or an intermediate step in the evolution of these taxa). Thus the required fertility/viability of all intermediate steps in the divergence of two taxa places constraints on which incompatibilities are possible and which are not, a point that will recur.

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(figure 1 is on p 1806 and shows the divergence of two theoretical populations with genetic mutations, ie - a → A, b → B, etc)This basically is the potential for genetic incompatibility and requires at least two exclusive mutations, and the first of the untested compatibilities is AB.These untested compatibilities do not occur with all existing alleles in a population.Enjoy

There's the possibility of an injection of DNA from the milkman.