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any examples of common ancestors?

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Are there any currently living species that could be considered a common ancestor to any other species? Also, have any actual common ancestors in the fossil record been identified? If not, is it because the concept of a common ancestor is more of a theoretical determination? In other words, we know that evolutionary theory requires common ancestors but we have no way to make an absolute identification and can only suppose that a particular fossilized creature could potentially be a common ancestor to something else?

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out of my head I can think that the Doberman and the Shitzu both evolved from the wolf and the three are very different, but I guess that is easy because they are subespecies rather than species, but other taxa of recent speciation may also qualify, I jsut do not know which...

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Rather by definition, a "common ancestor" of two extant species cannot itself be extant. Many groups/individuals/traits are derived in relation to others. E.g. in this example, the common ancestor of the fish groups was a generalist carnivore. Scale feeders have evolved from this common ancestor, while others have maintained the generalist carnivore trait. The scale feeders are derived in relation to the extant generalist carnivores, but none of the extant taxa are, or could be the common ancestor, as the common ancestor can no longer exist given it has evolved into a number of different forms.

 

1471-2148-7-195-4-l.jpg

 

 

Also, the process of biological diversification is a continuum, with the category of "species" being somewhat arbitrary. One generation does not immediately give birth to another species - the parent and offspring remain the same species at all times - the process is incremental in nature. As such, pinpointing an exact phenotype/genotype "common ancestor" between two related species is not possible.

 

 

In an attempt to explain better I will steal this image from Presgraves and Yi 2009.

 

1-s2.0-S0169534709001906-gr2.jpg

 

Imagine there is a Y axis with time along it. For the duration of t1 divergence is occurring between the populations which will become humans and chimps, but they are not yet at a point at which one would consider them separate species until the beginning of t2. The population that existed prior to the beginning of t2 has become the divergent chimp and human populations. In doing so, it cannot be extant at the same time as the species derived from it. In addition, the period of t1 will be a number of generations relative to effective population size. Prior to t1, stochastic drift will play a role in temporal divergence of the entire population, so the population may well be considered different species at different precise time point during the t1.

 

So, in summary, the term "common ancestor" used in the literal sense, doesn't really take into account the continuous nature of evolution, the coalescent processes of speciation or the dynamic of stochastic drift. "Common ancestral population" may be a more appropriate way to phrase the term.

Edited by Arete

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why cant an ancestor be such and be extant? My father and my grandparents are my ancestors even if they are alive when I am alive... So... Why could this not apply to species? It just makes no sense

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Because speciation occurs over a longer time period than two generations.

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My first guess would be that divergence is a branching process between populations which are not static. The parent and grandparent analogy doesn't fit in this respect.

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My first guess would be that divergence is a branching process between populations which are not static. The parent and grandparent analogy doesn't fit in this respect.

 

Because speciation occurs over a longer time period than two generations.

 

Ok but it does not need to happen in two generations... you can make a distinction between a polar bear and a sun bear... a distinction between a horse and a zebra, a distinction between a lion and a tiger, a distinction between a cat and a dog, a distinction between a bonobo and a human... you can determine they are different species becuase they are physically different and they are genetically different and of the pairs I have described only few of them can produce offsprings but these offsprings are necessarily infertile if not often infertile or infertile based on gender... Now... By definition of what "ancestor" means if you have a species from which another species or subespecies developed it does not matter whether the older species is extinct or not, it is the ancestor species... Wolves are ancestors of dogs... It does not matter if they are not extinct... by this logic it is perfectly valid to say that the red junglefowl is an ancestor of the chicken... The Sus scrofa is the ancestor of the Sus domesticus... Et cetera...

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A) Not sure what hybridization has to do with speciation in this sense - care to clarify?

 

B) You've picked a suite of domesticated organisms as examples. These are by and large not representative of diversification under natural settings due to the extreme levels of selection placed on very small initial populations over series of generations - selection in the fast lane so to speak. You will not find natural analouges to these examples in the same time frames. Under a number of species definitions, these domestic variants would not be considered species given incomplete reproductive isolation and limited genetic divergence at neutral loci. In some feral populations of domestic animals, a rapid morphological transition back to a wild phenotype is observed.

 

http://www.sciencedirect.com/science/article/pii/0376635789900326

 

C) Wolves, junglefowl and wild pigs didn't stop evolving at the point in time that humans separated a population from the whole and domesticated it. The original, homogeneous population from which these organisms were selected from exists at a time point in the past and the current populations are subject to ongoing evolution through stochastic and selective processes. There is a point at which the contemorary extant wolf will no longer be the same species as the wolf at the time of domestication. Without needing to infer and extinction event, the common ancestor of wolves and domestic dogs will no longer exist.

Edited by Arete

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Part of my point was that even in the case of long-term relative morphological stasis evolution has not "turned off" and an extant population that is most similar to a common ancestor is not the same as that common ancestor. The common ancestor of wolves and dogs was neither a dog nor a modern wolf. Et cetera. Even if there are ambiguous cases this is the proper shape of species diversification as I understand it.

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I get the point, sort of. But I don't see the logic. As an example, consider the cat family. Lions, tigers, leopards, cougars, cheetahs, etc. all came from one catlike ancestor. By what principle can we think that that ancestor must be extinct? Not all of its offspring will necessarily be transitioning into other species, and so we could expect this species to continue existing. But while some of the descendents remain the same, other descendents could be evolving into new species. Maybe this should not be a common occurrence, but it would not seem too much to think that we could find at least one example of this in nature.

 

Having said that, the more important question I was asking is if we have specifically identified any common ancestors in the fossil record. Is this a determination that could actually be made, or do the fossils simply not provide enough information about the creature in order to make more detailed comparisons with modern-day species?

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A) Not sure what hybridization has to do with speciation in this sense - care to clarify?

 

B) You've picked a suite of domesticated organisms as examples. These are by and large not representative of diversification under natural settings due to the extreme levels of selection placed on very small initial populations over series of generations - selection in the fast lane so to speak. You will not find natural analouges to these examples in the same time frames. Under a number of species definitions, these domestic variants would not be considered species given incomplete reproductive isolation and limited genetic divergence at neutral loci. In some feral populations of domestic animals, a rapid morphological transition back to a wild phenotype is observed.

 

http://www.sciencedi...376635789900326

 

C) Wolves, junglefowl and wild pigs didn't stop evolving at the point in time that humans separated a population from the whole and domesticated it. The original, homogeneous population from which these organisms were selected from exists at a time point in the past and the current populations are subject to ongoing evolution through stochastic and selective processes. There is a point at which the contemorary extant wolf will no longer be the same species as the wolf at the time of domestication. Without needing to infer and extinction event, the common ancestor of wolves and domestic dogs will no longer exist.

 

a). I understand that species are distinguished based on their ability to produce fertile offsprings one with each other, that is why I mentioned hybridization

 

b).yes I know domestication is evolution at the fast lane but that is the same reason we can detect evolution happening at domestication so that is why I chose domesticated animals as examples...

 

C)Wolves have not stopped evolving but since domestication is evolution in the fast lane the evolution of wolves, junglefowl and wild pigs is not fast enough to make the pre-domestication wolves significatnly different than current wolves, wild pigs and junglefowls... First a new species is such when it has outgrown the ten percent of the older species, second it is a different species when it cannot produce fertile hybrids with the parent species... Third, their must be some degree of uniqueness in its genotypes and phenotypes...

 

Part of my point was that even in the case of long-term relative morphological stasis evolution has not "turned off" and an extant population that is most similar to a common ancestor is not the same as that common ancestor. The common ancestor of wolves and dogs was neither a dog nor a modern wolf. Et cetera. Even if there are ambiguous cases this is the proper shape of species diversification as I understand it.

 

Evolution in nature is too slow to allow for ancestors of domesticated animals (which have evolved faster by artificial selection) to have evolved into anything different than what they were when humans domesticated a portion and generated the domesticated spinoffs... Furthermore, in nature evolution has varying speeds depending on changes in the conditions and of migration to places with new conditions and isolation after migration... This means that a population can stay the same in the region it originated but evolve where it migrated to and thus the ancestor and descendant cohabit the same place.

 

I get the point, sort of. But I don't see the logic. As an example, consider the cat family. Lions, tigers, leopards, cougars, cheetahs, etc. all came from one catlike ancestor. By what principle can we think that that ancestor must be extinct? Not all of its offspring will necessarily be transitioning into other species, and so we could expect this species to continue existing. But while some of the descendents remain the same, other descendents could be evolving into new species. Maybe this should not be a common occurrence, but it would not seem too much to think that we could find at least one example of this in nature.

 

Having said that, the more important question I was asking is if we have specifically identified any common ancestors in the fossil record. Is this a determination that could actually be made, or do the fossils simply not provide enough information about the creature in order to make more detailed comparisons with modern-day species?

 

I dont know why Dmehlinh is defending my post but he is completly right about what he says... Mmmm... Is he the original poster? So he is defending his question? Are you the original poster Dmehlinh?

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I get the point, sort of. But I don't see the logic. As an example, consider the cat family. Lions, tigers, leopards, cougars, cheetahs, etc. all came from one catlike ancestor. By what principle can we think that that ancestor must be extinct? Not all of its offspring will necessarily be transitioning into other species, and so we could expect this species to continue existing. But while some of the descendents remain the same, other descendents could be evolving into new species. Maybe this should not be a common occurrence, but it would not seem too much to think that we could find at least one example of this in nature.

 

Having said that, the more important question I was asking is if we have specifically identified any common ancestors in the fossil record. Is this a determination that could actually be made, or do the fossils simply not provide enough information about the creature in order to make more detailed comparisons with modern-day species?

 

Sorry I keep posting the same thing… My Internet connection keeps going out. Didn't realize it had already gone through.

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Dogs and wolves, although considered different species normally, can interbreed and produce fertile offspring. So even though they are different species in some aspect, they do not interbreed under 'natural conditions', they are not different enough to say they are completely distinct genetically. The same thing happens with ring species. So to say that current wolves are their ancestral species wouldn't necessarily be correct, but at the same time it wouldn't be wrong to say that a type of wolf was the ancestor of them both.

 

As to identifying an exact ancestral species for two related species is near impossible because there isn't an exact point to say that speciation happened here. I think Arete's post did a good job explaining that though.

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Dogs and wolves, although considered different species normally, can interbreed and produce fertile offspring. So even though they are different species in some aspect, they do not interbreed under 'natural conditions', they are not different enough to say they are completely distinct genetically. The same thing happens with ring species. So to say that current wolves are their ancestral species wouldn't necessarily be correct, but at the same time it wouldn't be wrong to say that a type of wolf was the ancestor of them both.

 

Which dogs? There are many breeds of dogs that would die if they mated with a wolf (if the dog breed is female) and many dog breeds where a male dog wont be able to fertilize a female wolf... Maybe the differences are physical and mechanical but not genetic, but they are still good enough to avoid this mingling... Now, I dont know if red junglefowl and chickens can mate or if wild pigs and domesticated pigs can mate. But now... If we "resurrected" aurochs through the same theory applied on Jurassic Park (cloning... with aurochs it is more feasible than with dinosaurs becuae their dna is easier to find) I bet they could mate with modern cattle succesfully, but we still consider aurochs to be ancestors of cattle (and the idea "aurochs are not extant so they can be considered ancestors" does apply with them)... Ancestry is between taxas of any kind... Species and subspecies, so it is moot point whether tehnically dogs and wolves are just differentiated in that dogs are a subspecies, wolves still are ancestors to dogs...

 

As to identifying an exact ancestral species for two related species is near impossible because there isn't an exact point to say that speciation happened here. I think Arete's post did a good job explaining that though.

 

It explains how you cannot pinpoint it, but not why ancestry should be just "extinct" species.

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a). I understand that species are distinguished based on their ability to produce fertile offsprings one with each other, that is why I mentioned hybridization

 

False. Plenty of species can hybridize and produce viable offspring. http://en.wikipedia...._hybrid_animals http://en.wikipedia....9#Hybrid_plants

 

Reproductive isolation, while a secondary characteristic indicative of speciation has not been considered a prerequisite condition for recognition as a species since the advent of the biological species concept. http://www.pnas.org/...ppl.1/6600.full

 

Since Ray and Mayr in the 40's, species have been defined primarily as "independently evolving metapopulations" by which defining characters such as genetic, morphological and ecological differneces, reproductive isolation, etc are secondary characteristics which are useful to identify these metapopulations - but the key factor is an independent evolutionary trajectory.

 

b).yes I know domestication is evolution at the fast lane but that is the same reason we can detect evolution happening at domestication so that is why I chose domesticated animals as examples...

 

Still, a) We don't see reproductive isolation between these domestic lineages and their wild congeners, b) we see a rapid return to a wild phenotype in feralized populations. This is evidence that the speciation process of these domestic populations and their wild relatives is incomplete. We also don't see two deruvative species and a remaining extant ancestor. By definition, if an ancestral population has evolved into one or more deruvative species, the ancestral population does not exist in the same state it did at the time of divergence.

 

C)Wolves have not stopped evolving but since domestication is evolution in the fast lane the evolution of wolves, junglefowl and wild pigs is not fast enough to make the pre-domestication wolves significatnly different than current wolves, wild pigs and junglefowls... First a new species is such when it has outgrown the ten percent of the older species, second it is a different species when it cannot produce fertile hybrids with the parent species... Third, their must be some degree of uniqueness in its genotypes and phenotypes...

 

Precisely - the current population of wolves IS NOT the same either phenotypically or genetically as the ancestral population from which dogs were isolated from. That ancestral population no longer exists. The "common ancestral population" of wolves and dogs no longer exists. A population will evolve stochastically over time. At some point current wolves will be considered taxonomically distinct from the ancestral population from which domestic dogs split from 10-15,000 years ago. At that point we will have two derivative species evolved from a common ancestor - dogs and "post-wolves" but no wolves - is that any clearer?

 

 

Which dogs? There are many breeds of dogs that would die if they mated with a wolf (if the dog breed is female) and many dog breeds where a male dog wont be able to fertilize a female wolf... Maybe the differences are physical and mechanical but not genetic, but they are still good enough to avoid this mingling... Now, I dont know if red junglefowl and chickens can mate or if wild pigs and domesticated pigs can mate. But now... If we "resurrected" aurochs through the same theory applied on Jurassic Park (cloning... with aurochs it is more feasible than with dinosaurs becuae their dna is easier to find) I bet they could mate with modern cattle succesfully, but we still consider aurochs to be ancestors of cattle (and the idea "aurochs are not extant so they can be considered ancestors" does apply with them)... Ancestry is between taxas of any kind... Species and subspecies, so it is moot point whether tehnically dogs and wolves are just differentiated in that dogs are a subspecies, wolves still are ancestors to dogs...

 

This is simply false. Domestic dogs of all breeds can produce viable offspring with wolves. Domestic breeds represent the most severe mutations possible in a population - the outliers of a distribution of phenotypic variation. They are the "tree men" "werewolves" and "dwarves" of the dog world. http://urbantitan.co...into-a-monster/ despite displaying severe mutations, "tree man" and "dog boy" are unequivocally human. If you ask prof. Bob Wayne who has worked extensively on dog ancestry, divergence between dogs and wolves isn't extensive enough to warrant species status and were reclassified back to Canis lupus in 1993 given genetic evidence. http://dogtalk101.bl...on-of-dogs.html http://en.wikipedia.org/wiki/Dog

 

Your assertion that aurochs would be able to breed with modern day cattle is pure Jurassic Park science fiction. We have no DNA evidence to support such an assertion and the morphological divergence and temporal displacement between the two populations is highly suggestive of significant divergence representative of significant evolutionary distinction between the two.

Edited by Arete

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False. Plenty of species can hybridize and produce viable offspring. http://en.wikipedia...._hybrid_animals http://en.wikipedia....9#Hybrid_plants

 

 

False? Only when you consider that my claim needs hybridization to reproduce sterile creatures more often than not... Tell me about hybrids that tend to be fertile rather than tenbding to be sterile and you can claim my point is false... I do not touch the case of plants becuase with them you can have chimnerization that makes it hard to determine when hybridization has produced fertile offspring or actually chimerization has happened.

 

Reproductive isolation, while a secondary characteristic indicative of speciation has not been considered a prerequisite condition for recognition as a species since the advent of the biological species concept. http://www.pnas.org/...ppl.1/6600.full

 

Since Ray and Mayr in the 40's, species have been defined primarily as "independently evolving metapopulations" by which defining characters such as genetic, morphological and ecological differences, reproductive isolation, etc are secondary characteristics which are useful to identify these metapopulations - but the key factor is an independent evolutionary trajectory.

 

Ernst Mayr proposed that... Was his position accepted by every serious biologist (non-creationist by definition of course) or at least by the majority? How do you determine a metapopulation to be independetly evolving? How doy ou determine it is a metapopulation and not a population?

 

Still, a) We don't see reproductive isolation between these domestic lineages and their wild congeners, b) we see a rapid return to a wild phenotype in feralized populations. This is evidence that the speciation process of these domestic populations and their wild relatives is incomplete. We also don't see two deruvative species and a remaining extant ancestor. By definition, if an ancestral population has evolved into one or more deruvative species, the ancestral population does not exist in the same state it did at the time of divergence.

 

Which dog breeds has this been tested with? Any of the toy dogs, lap dogs, purse dogs, micro dogs or mini dogs? I bet none of those are capable to survive in the wild on their own instinct and abilities or that they revert to anything like wolves... Maybe they take badger or rat-like characteristics but not wolf-like... Convergent evolution would probably result in thus as they are not fit to fill the niche of the true wolf. Have you evidence to the contrary?

 

Precisely - the current population of wolves IS NOT the same either phenotypically or genetically as the ancestral population from which dogs were isolated from. That ancestral population no longer exists. The "common ancestral population" of wolves and dogs no longer exists. A population will evolve stochastically over time. At some point current wolves will be considered taxonomically distinct from the ancestral population from which domestic dogs split from 10-15,000 years ago. At that point we will have two derivative species evolved from a common ancestor - dogs and "post-wolves" but no wolves - is that any clearer?

 

Actually, linguistically if your position were right we would call those "pre-wolves" because the word "wolf" is applied to the wolves as modern humans have known them, which are necessarily the same wolves that are living nowadays... But evolution cant be fast enough to give any sign of phenotypic change between pre-domestication wolves and current wolves and anyway, even then it does not matter, my position in this respect is that there is a known ancestor common to two taxas, that of wolves and dogs, (namely these taxas are subspecies or a type species and a subspecies). The problem is not that your position is not understood, the problem is that I do not believe it to be logically possible or to be true and I need evidence.

 

This is simply false. Domestic dogs of all breeds can produce viable offspring with wolves. Domestic breeds represent the most severe mutations possible in a population - the outliers of a distribution of phenotypic variation. They are the "tree men" "werewolves" and "dwarves" of the dog world. http://urbantitan.co...into-a-monster/ despite displaying severe mutations, "tree man" and "dog boy" are unequivocally human. If you ask prof. Bob Wayne who has worked extensively on dog ancestry, divergence between dogs and wolves isn't extensive enough to warrant species status and were reclassified back to Canis lupus in 1993 given genetic evidence. http://dogtalk101.bl...on-of-dogs.html http://en.wikipedia.org/wiki/Dog

 

I have never claimed that the dog is a different species, I have claimed it is a different and unique subespecies, a different taxa if you wish. Actually each breed should be considered a unique taxa (maybe a different infraspecies if the term is allowed as a taxa inside subspecies, sidenote, human races, a fiction, and human ethnias, an anthropological tool, would not qualify as infraspecies because hybridization is not flawed between human races or human ethnias but between dog breeds hybridization is flawed)...

 

As for the claim that it is false that some breeds cannot have viable offspring with wolves I stand by this fact because I know for certain that some breeds;

1.Cannot have natural birth

2.Cannot survive pregnancy with a puppy from the other breed

3.Cannot impregnate some other breeds

 

The reason for 2 and 3 is not genetic but what in tv tropes and bulbapedia is known as "hot skitty-on-wailord action", http://bulbapedia.bu....net/wiki/HSOWA so you see, you have the fictional idea of the extremely smalls eevee, rattata, seedot, skitty and diglett merging with wailord, these are all fictional creatures from pokemon franchise of which I found out by investigating on the subject of fiction on tv tropes... Common sense shows that equivalents would not work in real life... And your human-dog analogy is failed because male human dwarves are not incapable of fertilizing normal female humans and female human dwarves never have children with normal male humans (if I am wrong provide evidence to the contrary but men never fell in love with female dwarves but the way sexism is structured women do accept shorter, dwarven men as mates and partners because they do not care about looks as much as they care abotu personality and economical situation)...

 

I dont remember the dog breed, boxers or bulldogs or some similiar dog breed cannot survive natural birth because of how their bodies are formed so they cannot produce offsprings with wolves unless artificial mingling is done...

 

your human and dog analogy would be realistic if human variability were extreme as breed variability... If you had 13 cm tall human breeds and 4 meter tall human breeds, well, maybe we do not need that much height, lets heep the 2.72 m height maximum of real world humans and add a breed 13 cm tall... Even that would be sensible... But humans have no breeds, the 2.72 m tall human is not that tall because he belongs to a special breed, he is that tall because his pitituay gland failed... The shortest human is not 54.6 cm tall because his breed tends to make people that short but because he was a random genetic mutation, a minor flaw, yet he would not inherit his height to his children.

 

Your assertion that aurochs would be able to breed with modern day cattle is pure Jurassic Park science fiction. We have no DNA evidence to support such an assertion and the morphological divergence and temporal displacement between the two populations is highly suggestive of significant divergence representative of significant evolutionary distinction between the two.

 

My assertion is not sci-fi, you have made your arguments with so much seriousness, you dont need to get offensive now by calling it Jurassic Park sci-fi (did ya get the idea from my mention of it before? So it seems),,, My assesrtion is a bet and speculation based on the idea that evolution takes too much time for aurochs to possibly be so genetically distinct from modern cattle as to prevent non-sterile hybridization between them. Yet, even as speculation I began defending the position I began defendign as criticism against the notion that an ancestor, to be such must be dead/extinct when the word "ancestor" both etymologically and historically (and by historically it means "up to these times") have always meant "that precedes in philogeny in a genealogical tree or philogenetic tree or taxonomic tree" not that it means "extinct/dead predecessor".

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False? Only when you consider that my claim needs hybridization to reproduce sterile creatures more often than not... Tell me about hybrids that tend to be fertile rather than tenbding to be sterile and you can claim my point is false... I do not touch the case of plants becuase with them you can have chimnerization that makes it hard to determine when hybridization has produced fertile offspring or actually chimerization has happened.

 

Plenty of vertebrates, plants, invertebrates and other organisms of different species hybridize to produce viable hybrid offspring. It's a considerable area of research in population genetics.

 

E.g.

http://www.scienceda...70430123849.htm

http://onlinelibrary...0049.x/abstract

http://onlinelibrary...03.01905.x/full

http://www.publish.c...paper=MU9870158

 

etc.

 

Ernst Mayr proposed that... Was his position accepted by every serious biologist (non-creationist by definition of course) or at least by the majority? How do you determine a metapopulation to be independetly evolving? How doy ou determine it is a metapopulation and not a population?

 

Actually it was first proposed by John Ray. http://scienceblogs....l_species_c.php but popularized and refined by Mayr following the emergence of the field of genetics.

A refinement of it - the evolutionary species concept is the most universally accepted species concept in biology today: http://sysbio.oxford...s=1&ssource=mfc

As I tried to explain earlier - this concept allows for integrative/dynamic detection and delimitation of species, having defined them as metapopulations with independent evolutionary histories. A number of emergent delimitation methods are currently in various stages of development. There is no universal characteristic by which they are identified - which is a much better reflection of the reality of diversification than relying on a sole characteristic like reproductive isolation. http://www.pnas.org/...4/27/0913022107 http://sysbio.oxford...t/59/1/59.short etc.

 

 

Which dog breeds has this been tested with? Any of the toy dogs, lap dogs, purse dogs, micro dogs or mini dogs? I bet none of those are capable to survive in the wild on their own instinct and abilities or that they revert to anything like wolves... Maybe they take badger or rat-like characteristics but not wolf-like... Convergent evolution would probably result in thus as they are not fit to fill the niche of the true wolf. Have you evidence to the contrary?

I linked you to scientific study on feralization in a previous post. The research was not specific to dogs. http://www.sciencedi...376635789900326

There's a fair bit or research on reversion to wild phenotypes in domesticated species. http://aac.asm.org/c...9/3175.full.pdf http://content.karge...roduktNr=230659

 

 

 

Actually, linguistically if your position were right we would call those "pre-wolves" because the word "wolf" is applied to the wolves as modern humans have known them, which are necessarily the same wolves that are living nowadays... But evolution cant be fast enough to give any sign of phenotypic change between pre-domestication wolves and current wolves and anyway, even then it does not matter, my position in this respect is that there is a known ancestor common to two taxas, that of wolves and dogs, (namely these taxas are subspecies or a type species and a subspecies). The problem is not that your position is not understood, the problem is that I do not believe it to be logically possible or to be true and I need evidence.

 

Wolf populations show genetic turnover and differentiation on much smaller time scales than 10,000 years. http://onlinelibrary...06.02877.x/full An example is melanistic differences between grey wolf populations driven by environmental selection http://www.sciencema.../5919/1339.full

 

It's almost certain that the wolf population from which domestic dogs were originally derived from was genetically and phenotypically distinct from wolf populations today - especially given the sever bottleneck that wolves have been through in the intervening time.

 

 

I have never claimed that the dog is a different species, I have claimed it is a different and unique subespecies, a different taxa if you wish. Actually each breed should be considered a unique taxa (maybe a different infraspecies if the term is allowed as a taxa inside subspecies, sidenote, human races, a fiction, and human ethnias, an anthropological tool, would not qualify as infraspecies because hybridization is not flawed between human races or human ethnias but between dog breeds hybridization is flawed)...

 

 

 

As for the claim that it is false that some breeds cannot have viable offspring with wolves I stand by this fact because I know for certain that some breeds;

1.Cannot have natural birth

2.Cannot survive pregnancy with a puppy from the other breed

3.Cannot impregnate some other breeds

 

Physcial inability of domestic breed to give birth or copulate is not evidence of evolutionary distinction and therefore speciation - a great dane and a dachshund are still both dogs - albeit at different ends of a highly phenotypically diverse spectrum. As I tried to explain - dog breeding selects for phenotypic outliers and the outlier populations do not represent distinct metapopulations - but highly plastic phenotypes heavily selected for over a small number of generations. As an example of the lack of differentiation between wolves and domestic dogs:Gene flow between dogs and wolves happens: http://onlinelibrary...06.02995.x/full http://www.springerl...h6dbrfwhcl09t3/ and dogs were probably derived from multiple wolf populations and certain dog breeds are more related to wolves than they are to each other. : http://www.sciencema.../5319/1687.full

 

 

 

 

My assertion is not sci-fi, you have made your arguments with so much seriousness, you dont need to get offensive now by calling it Jurassic Park sci-fi (did ya get the idea from my mention of it before? So it seems),,, My assesrtion is a bet and speculation based on the idea that evolution takes too much time for aurochs to possibly be so genetically distinct from modern cattle as to prevent non-sterile hybridization between them. Yet, even as speculation I began defending the position I began defendign as criticism against the notion that an ancestor, to be such must be dead/extinct when the word "ancestor" both etymologically and historically (and by historically it means "up to these times") have always meant "that precedes in philogeny in a genealogical tree or philogenetic tree or taxonomic tree" not that it means "extinct/dead predecessor".

 

Sorry you took offense, none was intended.

 

I think a lot of the misunderstanding based on your use of reproductive isolation as a hard criterion for species delimitation, and the misapplication of that concept to dog breeds. Even in the absence of divergence, if a contemporary population arises from an ancestral population, The ancestral population cannot simultaneously exist at the same time point as the derived population (unless you have a DeLorean I guess). If we consider contemporary species to be the same as their ancestors, chickens are really velociraptors, which are really amphibians, which are really fish, etc.

Edited by Arete

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B) You've picked a suite of domesticated organisms as examples.

If it's good enough for Darwin it's good enough for me.

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If it's good enough for Darwin it's good enough for me.

 

Darwin didn't exclusively look at domestic animals then extrapolate what he saw to natural systems. ;)

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I apologize for interrupting an interesting conversation about hybridization, but this discussion got me thinking about Gingko biloba. This tree is often called "a living fossil", with the implication that this species has been around for a long time (much like lake sturgeon). However, I wonder, was G. biloba around millions of years ago (since the Cenozoic, right?), or just its genetically and phenotypically different-yet-similar ancestor that happens to have the same species name because there's no distinct speciation event in the fossil record? Ditto for lake sturgeon.

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low rates of phenotypic evolution/strong stabilizing selection means that certain organisms don't change very much over long periods of time. Crocodiles are another good example. The forces of purifying selection on selectively advantageous traits can make diversifying to a novel fitness optima highly unlikely, and as a result, things that work well for an organism through the range of environmental fluctuations remain. It it ain't broke...

 

I said it in my first post - speciation is largely a population process and "common ancestors" are better thought of as "common ancestral populations" rather than species. :)

Edited by Arete

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So, are you saying that if we were somehow able to procure genetic data from an ancestral crocodile, or G. biloba, or sturgeon, we wouldn't see any significant difference, even in, say, genes that code for disease resistance or junk dna?

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No - I'm saying that the phenotype has been conserved (and presumably the genes underlying the phenotypic traits in question also). Noncoding genetic regions and genes not under positive selection will of course be subject to stochastic drift.

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Sorry you took offense, none was intended.

 

I think a lot of the misunderstanding based on your use of reproductive isolation as a hard criterion for species delimitation, and the misapplication of that concept to dog breeds. Even in the absence of divergence, if a contemporary population arises from an ancestral population, The ancestral population cannot simultaneously exist at the same time point as the derived population (unless you have a DeLorean I guess). If we consider contemporary species to be the same as their ancestors, chickens are really velociraptors, which are really amphibians, which are really fish, etc.

 

I cannot contend your other arguments... I am not saying we consider contemporary species to be the same as their ancestors, only that they are the same to those ancestors that are phenotipically and genetically the same... But your point is reduction ad absurdum... I could apply it to your point too... Am I a different spcies from my paternal grandfather because he died before I was born? Am I and my family a different species than the grandparents of the grandparents of our great grandparents? My point is that ancestry for individuals means "earlier in the phylogenetic genalogic tree" and for species it is the same but with the added feature of "with genetic and phenotypic divergence big enough to consider them different species"; extinction or lack of it has no role on this definition nor it needs to have a role...

 

 

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I cannot contend your other arguments... I am not saying we consider contemporary species to be the same as their ancestors, only that they are the same to those ancestors that are phenotipically and genetically the same... But your point is reduction ad absurdum... I could apply it to your point too... Am I a different spcies from my paternal grandfather because he died before I was born? Am I and my family a different species than the grandparents of the grandparents of our great grandparents? My point is that ancestry for individuals means "earlier in the phylogenetic genalogic tree" and for species it is the same but with the added feature of "with genetic and phenotypic divergence big enough to consider them different species"; extinction or lack of it has no role on this definition nor it needs to have a role...

 

OK...

 

Let's go right back to the start. A) as the process of speciation is a population process and b) the categorization of species is effectively an arbitrary delineation on this continuous process; is it possible to consider "common ancestors" as "common ancestral populations"? The concepts and processes behind diversification are much easier to understand once we can discuss them as such.

 

Now, are we in agreeance that you are not part of the homogenous population that your grandfather was? This means you are not free to breed with the same individuals he was due to the temporal gap and generational turnover that occurs in humans. As an aside, humans are unusual in the biological world by having overlapping generations - so the effect of population differentiation on generational scales is usually more pronounced in other organisms.

 

Let's take it one more step backwards - the population, as defined above to which our great-great grandparents belonged to is no longer with us - in the sense that this population of humans is no longer contributing directly and significantly to the gene pool of the next generation. As such - it is not possible for the simultaneous existence of an interbreeding population of our great - great grandparents and a population of our own generation; thus it is not possible for a population of our ancestors and our own to be simultaneously extant.

 

Now if we go even further backwards - the common ancestral population which became - through the population level process of diversification over several generations humans and chimps, by the same logic as the impossibility of the co-existence of our great-great grandparents and our own generation - cannot be extant. Now the difference here is that most biologists are content to place the arbitrary delimitation of this common ancestral population as being representative of a species distinct from its deruvatives - the chimps and the humans.

 

As such, it is not possible for the common ancestor of two derivative species to be simultaneously extant as the derivatives. It's not reduction ad absurdum because we understand the process by which population differentiation occurs and based on this process we understand it to be not possible.

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