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dmehling

any examples of common ancestors?

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The population structure of all extant animals is unknown and different groups of humans use different terminology to describe variants below the level of species. Wikipedia is also not an authority on vertebrate diversity.

 

1.True, wikipedia is not an authority, but it is a center of scientific, philosophical and other kind of information popularizing/divulgation as such it would be convenient if its pages had this information provided however I understand the other reasons you give for it not being the case so...

 

2.The population level of extant animals (and even of extinct animals) must be known before non-specialists and crossfield professionals can use these in their studies, don't ya think?

 

3.Science needs a single terminology, that is why Linnæus' work on inventing taxonomy is so important to science... That is why the periodic table provides a unique code for chemistry... Actually we need more unambigous terminology, not only for science but for any field of knowledge... If different scientists use different terminology to distinguish one population from another then studies on the subject of population must always specify their terminology and even then their usefulness is limited, a common terminology must be stablished for all scientists.

 

As a concept, panmixia is a binary condition. Either all individuals in a given sample mate at random, or they don't. In reality, perfect panmixia doesn't exist, but using genetic tools we can evaluate significant deviations from the assumptions we make of panmictic populations.

 

Ok

 

Humans are not panmicitic at all and cluster genetically according to geographic region http://pritch.bsd.uc...nbergEtAl02.pdf

 

I tried following the link's claim but I could not make much of what it said because it relied on terminology and graphs I have not been taught to understand and interpret... however I saw that most of the claim is based on genetics on samples that could not be large enough to represent what they are meant to represent...

 

And it uses little consideration of anthropology, history, human geography (where behavioral geography is the one that serves the best), travel statistics and studies of migration and interracial or international breeding... I guessed (I admit it is just a hypothesis, but it is based on an educated guess) that humanity had to be the most panmicitic of all species because by distance travelled versus size per individual the human species is the species that travels the highest amount of distance through its lifetime on average (or maybe arthropods brake our record because they need to travel smaller distances to do so, however in that case we would still be the species that covers the greatest spread of coordinates per average individual, this is another hypothesis I admit)... I mean, there are higher chances that a Japanese man marries a Canadian woman that the chances that a polar bear breeds with an Andean bear... Because humans have the ability and the need to travel through the world (it may be an ability proportional to wealth but even the poorest person has some chance of being able to migrate and a motivation to do so)... I bet humanity is the only species where migration is a permanent option for individuals instead of an ocassional event for populations as a whole.

 

Sympatry refers to overlapping geographic distribution. If two populations occur in the same place, they are sympatric. Human populations in Asia are not sympatric with those in Europe. Migration occurs between these populations allowing for gene flow, but this is not the same as sympatry.

 

Asia may not be sympatric with Europe through most of Asia, but then you get Russia, Europe/Asia and Greece, Europe and Turkey, Asia where sympatry occurs between one population and the other...

 

You can consider races and class to be different populations (rarely do people of different races or different social classes mate together, it happens, but it is strange because racism and classism is very strong in the modern world, yet classes and races inhabit the same land; class is a stronger factor for division than race however because classism is stronger than racism and people of the same race but different class have less chances of forming a relationship between each other than people of the same class but different race... Most interclass relationships happen because movement between social class is possible and has always been possible, with different chances of occuring depending on the place and time)...

 

Biology, when applied to humanity, is much more complex than when applied to animals, anthropology is always involved, by necessity... and viceversa.

 

Human populations are not sympatric or panmicitic: http://pritch.bsd.uc...nbergEtAl02.pdf http://www.sciencedi...002929707605746

 

Inhabited land is continous throughout the major continents of America, Eurafrasia, Oceania and Polynesia... The later two has the greatest amount of inhabited territory because Polynesia is a continental archipielago and Oceania is Australia plus a continental archipielago... But within America and Eurafrasia you have a continuum of inhabited land, these means that you may have clear national boundaries but no clear boundaries between one population's geographic region adn the geographic region of the other population... Take Peru for example, the cities closest to Brazil have people that speak both Spanish and Portuguese because they often travel between both countries, likewise Tumbes, in the north, next to Ecuador, has people that cross the frontier to Ecuador very often, would this not mean that the populations are sympatric? I mean, it is not permanent migration, they rarely ever sleep in the foreign area, but they do visit it and interatc with its locals.

 

Glad you're coming around to understanding that hybridization can occur between species. It is an interesting field.

 

I agree it is an interesting field...

 

However when one determines that a word has a meaning and one finds something that seems to comply to that meaning in everything with the exception of one thing, the normal process is either to modify the word's meaning or to deny that the word corresponds to the example... So I say that I could accept interspecies breeding of non-sterile hybrids (as the heliconius is an example of such) or demand that the cases that do not fit this definition be reclassified (thus reclassifying those Heliconius treated as members of different species to one single species with high genetic variation), however the later could make species as meaningless as the concept of race (specially when the concept of horizontal gene transfer and asexual reproduction means that that the species problem is a strong problem in the subject of species delimitation). This means we need a better definition of species, one probably based on genetic make-up (we know for example that chimpanzees share 98% of their genes with humans and we are sure that chimpanzees and humans are not the same species, so we should determine that whatever the percentage of common genes between two individuals is it should be somewhere above 98% for them to be grouped in the same species). By answering the question "what measure is non-human" with genetic studies we can spread the ancient problem of essence (an ontological problem that can now expand to the species problem and become a taxonomic problem) to species (however for ethical purposes such as human rights we must still classify human on a biological and behavioural level; sociopaths, psychopaths, serial killers, rapists, cleptocrats and other biological humans that cannot feel empathy and are thus a threat to the wellfare of humanity must not be protected by human rights if humanity is where we invest our ethical and political interest)

 

I would still benefit from knowing which other species exhibit the capacity for hybrid swarms (preferibly if they are not arthropods, preferibly if they are vertebrates; under the hypothesis that there was no single primordial soup but that abiogenesis happened on many different places simultaneously because the conditions permitted so we can guess that without a link between some taxa and other taxas it is possible that they belong to different trees of life; for instance we know for certain that all hominids are related but the relationship between hominids and earthworms/cockroaches/algae/coral/sponges/squid is not supported by the same amount of evidence.). Besides, the argument can benefit from a greater list of examples of such species... But I am not the professional in the field of taxonomy so I cannot deny your arguments out of mere whim, all I can do is ask; how much mainstream is your position? And I have recieved examples of scientists supporting it but I have not seen statistics of how many professionals agree on it... Therefore I still do not know how mainstream it is (In science, unlike literature, being mainstream is the goal, in literature it means that you have no talent and need to do what everyone else often does).

 

One does not need to work on the level of meta-populations to conduct an evolutionary study. If the processes you are interested in happen at the population level that is the scale you work at. See population genetics, http://en.wikipedia....lation_genetics, phylogeography http://en.wikipedia..../Phylogeography landscape genetics http://webpages.icav...9/Papers/21.pdf etc.

 

This only makes me wonder some questions

 

1.How can you determine that the changes happen only on the population level before you have started your study?

 

2.How can you determine it only happens on the population level when you have not yet studied other populations?

 

3.How could it be pertinent to ethology or to branching ethology with anthropology if it only happens on the population level? I have not yet started to study anthropology or ethology on a university but as a person intersted on the fields I have done my best to learn everything I can about them and thus I can provide this question about their relationship which should involve evolution because if studying animals is pertinent to understanding humans it is because we understand that these animals are evolutionarily related to humans and the behavioral composition is similiar or indentical in many ways, this demands evolution to be something you can study on taxa above species, not only on the population level... but I guess other fields, such as ecology, may need similar studies on the metapopulation level.

 

Generational overlap has already been discussed in this thread at length. in post #25, I tried to explain at length the separation of populations on the temporal scale.

 

Ok, since at that point I had not yet agreed on the population/species divide and its necessity for the discussion of the subject of evolution I need to answer your claims from that post from where I am standing now, that is a different position that the one I held at the time... so I will quote you again, in order;

 

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.

 

I have accepted A for these reasons 1.I'm not the professional and 2.you have shown that those that propose speciation is a species process and thus define species based on interbeeding capability have failed to limit the term "species" to creatures that can breed with others in their own species but not with others in close species, therefore proving that the definition of species is not as strong as it should be to be of much value although you recongize that smaller taxa, like "evolutionarily significant unit" and "population" have no scientific consensus so thus they are still problematic...

 

As for B... I accept that under some definitions of arbitrary the categorization of species is effectively arbitrary, however I believe that professionals could (and should) build a better definition using the knowledge provided by genetic studies now that genomas are being cracked and we can determine, for example, that chimpanzees and humans share 98% of their genes. We could thus build two ways to classify animals; one based on morphology alone and one based on genetics/phylogeny alone...

 

The former would be useful for ecological and anthropological studies (the niche of an animal and thus the value of an animal to ecology is based on its morphology, their ecological value is also the value they have to humans and it is reflected in mythology so if we could classify animals on a morphological basis we would have an easier time understanding the relationship between humans and animals, which is often expressed in their mythology and in the mythic animals human societies have believed in, and even monsters of urban legend comply to this) while the later is pertinent to studies involving evolution (even if evolution takes place on a population level). Both taxonomies should have their own taxa (morphological taxa could for example have the category "draconic" which could be further divided into "serpentine", "chiroserpentine" and "non-serpentine").

 

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.

 

True, however, to some extent, my population and my parents' population is the same; I cannot breed with women of the generation of my mother because they have gone through menopause already, some years ago I could however, about a decade ago or so... On the other hand, women of my generation, including my sisters, can breed with men of my parent's generation because andropause is so different to menopause that not all men lose fertility with age.... Now I accept that humans can be different but I also accept that any studies human conduct are interested so much in benefitting humanity that there is a degree of importance to each subject regarding how useful the particular subject is to humanity... I cannot think of any evolutionary study more important to humans that the ones involving humanity itself so, under this principle, the effect of population differentiation on generational scales is an important subject... However we can still consider different generations to be different populations and sympatric populations at that, because interbreeding between them is unusual (women may be interested in older men more often than men in older men but even that has a limit which may vary between individuals but is such that it is unusual for women and men of different generations to breed together, men interested in older women are rarely interested on post-menopausic women and if they were no intergenerational breeding would happen, the greatest number of successful breeding for different generations took place at different moments in time)

 

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.

 

But this only works because you are taking it so many steps backwards it works... The problem still happens that parents and their children are of different generations and different populations but some interbreeding can take place. Migration is also more common to happen differently for members of different generations; My paternal grandfather and his parents-inlaw, or their parents, came from Italy to Peru, I wish I could eventually travel to study in the UK and even travel through many countries through the world and as a sexually active individual I will try seducing women wherever I go and chances exist that condoms fail and reproduction takes place, or I get a disease, I'm realistic but I hope the later does not happens and I hope I can afford the former if I get to travel... This may seem an anecdotical argument but I know for certain that this is not statistically unusual; humans do tourism through out the world or migrate every day, that is why the bussiness of airports, ports, airplanes, ships and such is a thriving bussiness. I can expect the same to be true about most people, even people with religious mores against sex tend to be sexually active (they are hypocrite about it, but they are sexually active). Humanity is too complex and advanced to be broken in terms applied to animals... Don't you think?

 

That was not the question in the OP. The question was "Is there any examples where the common ancestor of two or more derived species is still extant?" [paraphrased]. As was explained at length, the ancestral population of two derived species cannot co-exist with it descendants. Hence the wolves/dog ancestor being ancient wolves and not contemporary wolves.

 

I should quote the original poster without paraphrasing him;

 

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?

 

Ok, the problem is that the OP made two/four questions and then he or she made a conclusion from it, conclusion which he/she phrased as his/her third and fourth questions... I based my answer on the conclusion and on the second question he/she made, you based it on his/her first question... I think he/she implies that the theory of evolution is not really proven but that it is just a hypothesis we have accepted with insufficient evidence... Therefore I consider valuable to contend that we know that ancient wolves are the ancestors of modern wolves and dogs, therefore proving evolution for at least one circumstance.

 

Similarly to any other group of interest - examine genetic loci under natural selection for deviations from the assumptions of panmixia.

 

Can panmixia be studided through genetic analysis alone? Can't ecological and ethological studies on the behaviour and travel patterns of species/populations/esus and its individuals provide no complementary data? Maybe data on a higher scale since genetic studies are hard to conduct on the large scales which ecological and ethological studies can be handled?

 

This is not true either. The "environment" in terms of natural selection, is any external factor which interacts with your genotype to influence your ability to pass genes on to the next generation. E.g. A child's genotype confers it a severe allergy to penicillin. It is prescribed penicillin, suffers a anaphylaxic reaction and dies. The deleterious components of its genotype were selected against by the environment. The ability to adapt the environment to better suit you does not eliminate selection by it - it simply changes the selection pressures.

 

I agree that the "environment" in terms of natural selection, is any external factor which interacts with your genotype to influence your ability to pass genes on to the next generation...

 

My argument and my point and what I am proposing is that for humankind these external factors are more often than not sociological, anthropological and artificial rather than otherwise...

 

I mean, more often than not when a creature is analised its enviroment is qualified as the biome it inhabits and biomes vary based on geography, however I contend that humans have created their own biomeless-enviroment, one that trascends geography, not the city (the city is a biome for wild animals, even for cats that are somewhere between wild and domesticated but closer to the wild side than to the domesticated side) but the society;

 

the chances for a person to survive, even when the person does not lives in the city, are more related to his or her relation to the society to which he or she has higher amounts of links (whether he/she is a farmer living far from the outskirts of a city to which he/she sends what he/she produces or an investigator watching the behaviour of orangutans in the deepest jungles of Borneo or an investigator doing whatever research might bring him or her to an outpost in the antarctic or the arctic)... Rather than hunting like a wild animal through the city he or she inhabits a human's ability to survive is related to his or her ability on a field which may not even be related directly to production of wealth and food such as artists, showmen, bullfighters, politicians, philosophers, criminals (in the wild stealing food from another species is possible or from another member in one's population but this alone cannot be the method by which a creature can survive, among humans being "a career criminal" so to say is possible and criminals are a greater threat than wild lifeforms), theoretical physicist, pure mathematician, professional athletes (like Pele, Maradona, Tyson, Beckham, Michael Jordan, etc.) which means that humans can survive exclusively on their abilities to fit and exploit the human factor alone (even stupid people like Paris Hilton and Roland Emmerich can succeed on this skill alone so the skill does not demand intelligence or knowledge either; and endurance, manual manipulation and intelligence are often considered the source of humanity's success as a species yet we can see how, as individuals, success is limited to exploiting the power of popularity... Paris Hilton was not a nice person on her show and her show was very stupid, it promoted shallow and selfish behaviour and bullying those that have less money than oneself by pranking them behind their backs, but since people existed that looked up to that bitchyness she managed to earn enough money that when her grandfather left her without his economic support she no longer needed it to continue living among the wealthy; that a human like Paris Hilton, with no true talent, can, by making a show of how much she lacks talent, get as far as she has in our society is but evidence that humanity trascends biomes and it is an enviroment in itself, I know this is my hypothesis but what I have mentioned are evidences we both know to be fact... Likewise we can argue that people with a varying of conditions that would die without human support manage to breed thanks to the help they get from their jobs or relatives... Stephen Hawking is capable of reproducing dispite his crippling situation because he is not sterile as far as I understand and if someone is willing to help him ejaculate a sample of his semen can be used to impregnate a woman, nonetheless he is severely crippled, and just like Marilyn Monroe proposing Albert Eistein to have a child with her many women would want to have descendants with him, indeed he has been married twice and has three children. Jane Wilde and Elaine Mason, his former wives, were probably attracted in great deal mostly due to his skills than to any other factors, skills which made him well suited for the human factor but not for survival in the biomes that correspond to the geographic regions he has inhabited... I am taking this from wikipedia; "diagnosis of motor neurone disease came when Hawking was 21, shortly before his first marriage, and doctors said he would not survive more than two or three years". He is currently 70 years old so he has survived the condition for almost 5 decades and the same article says that it is unusual that he has survived for 5 rather than 1 decade. So we can know how strong is the human factor on survival, for example your claim about a severe allergy to penicillin could be countered by testing for allergies before applying the penicillin on the kid and trying an alternate cure on the child. By the time he was 32 years old, more or less, according to wikipedia, he was totally paralysed and yet it was about this time that he started his rise to celebrity status, he may be too old to be fertile now, I do not really know, but there has been a time when he was both fertile and admired by so many women that he had great chances of passing on his genes to more than three children despite no longer being adapted to a wild version of the enviroments he inhabited).

 

In other words I do not deny that enviroment, in the way you have defined it, has banished, under your definition there is always an enviroment, I only say that nowadays for most humans the enviroment is more artificial and human than it is natural. The selection pressures are now a subject that the human sciences, rather than than the natural sciences, would study, whether it be sociology, anthropology or psychology... I also wanted to add to the discussion an interesting subject on subdivisions to the species divide that do not seem to be populations nor do they seem to be subspecies... but I will add that at a later time. Anyway, do you agree with what I have claimed?

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