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Member (Idle past 4727 days) Posts: 283 From: Weed, California, USA Joined: |
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Author | Topic: The Common Ancestor? | |||||||||||||||||||||||||||||||||||||||||||||||
barbara Member (Idle past 4824 days) Posts: 167 Joined: |
If we take the human lineage completely out of the picture, how did the chimp, gorilla and orangutan diverge? Did both diverge from one? These 3 live in specific locations so its hard to grasp that they would have cross paths in history.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
|--------------- orangutans ---| | |----------- gorillas |---| | |--- chimps | |---| |---| |--- bonobos | |------- humans
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Having a specific individual that all our species can count as an ancestor doesn't seem outrageous to me. It seems outrageous to me, and for good reason. Hold your outrage. It would be remarkable if that individual uniquely held that distinction. It is inevitable that at least one individual did. In fact, let me blow your mind a little. There existed a common ancestor of all humans and chimps/bonobos who had two children, one of whom was the common ancestor of all living humans but no chimps/bonobos, and the other of whom was the common ancestor of all living chimps/bonobos but no humans.
Speciation does not show effects in single individuals. Quite so. And the two children I just mentioned might for all I know have been identical twins.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined: |
Common ERV's an excellent way to determine common ancestors ... Common ancestry.
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Strongbow Junior Member (Idle past 4932 days) Posts: 26 Joined: |
quote: Roger that... I misinterpreted your reply and misunderstood your postion. My apologies.
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Strongbow Junior Member (Idle past 4932 days) Posts: 26 Joined: |
quote: OK.... I'm a bit confused.... how do we know that? Why couldn't humans have descended from an individual from one part of the population, and chimps/bonobos descended from an individual in another part of the population?
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.4 |
There existed a common ancestor of all humans and chimps/bonobos who had two children, one of whom was the common ancestor of all living humans but no chimps/bonobos, and the other of whom was the common ancestor of all living chimps/bonobos but no humans. Are you sure about this? Could we see a proof?
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barbara Member (Idle past 4824 days) Posts: 167 Joined: |
Response to diagram on common ancestry. Could you please now add in Australopithecus, Homo habilis, Homo Rudolfensis, Homo Erectus, Homo Ergaster, Homo Heidelbergensis, Homo Neanderthal, Homo Cro-magnom, woodland apes. and then modern humans.
Thanks Woodland apes are australopithecine which may be the same as australopithecus. My error. Edited by barbara, : No reason given. Edited by barbara, : correction
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barbara Member (Idle past 4824 days) Posts: 167 Joined: |
I read that the genetic differences between chimps and bonobos is 3% and bonobos are chimps but are separated by boundaries, their social behavior is the complete opposite in that chimps are very aggressive while the bonobos are peaceful.
Another article said that our lineage split at the same time as the chimps did from a common ancestor. The 4% difference between us and chimps seems to put us farther back then chimps and bonobos.
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nwr Member Posts: 6409 From: Geneva, Illinois Joined: Member Rating: 5.3 |
Dr Jack writes:
While I have not fully thought it through, I'm inclined to think that Dr Adequate is correct. This would likely come from graph theory (part of combinatorics, which is a branch of mathematics). The family tree is a directed acyclic graph. Well, things get murky if eukaryotes arose from a symbiotic union of simpler organisms, but you don't have to take things back that far if your concern is with a common ancestor for humans and chimps.
Are you sure about this? Could we see a proof?
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Blue Jay Member (Idle past 2720 days) Posts: 2843 From: You couldn't pronounce it with your mouthparts Joined: |
Hi, Barbara.
barbara writes: Could you please now add in Australopithecus, Homo habilis, Homo Rudolfensis, Homo Erectus, Homo Ergaster, Homo Heidelbergensis, Homo Neanderthal, Homo Cro-magnom, woodland apes. and then modern humans. All of those are "humans" on Dr Adequate's diagram (except maybe for "woodland apes": I don't know what "woodland apes" are). -Bluejay (a.k.a. Mantis, Thylacosmilus) Darwin loves you.
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Dr Adequate Member (Idle past 306 days) Posts: 16113 Joined:
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Are you sure about this? Could we see a proof? Hmmph. Actually, I'm having trouble making the last part of the argument truly rigorous. For now, let's go for a weaker proposition: there was at least one individual having two children one of whom was ancestral to some or all living humans but no chimps/bonobos, and the other of whom was the ancestor of some or all living bonobos/chimps but no humans. --- Consider humans, chimps, bonobos, the common ancestral species and all the intermediate species. Call this set Z. We can divide set Z into four mutually exclusive sets: Set O: those with 0 living descendants. Set H: those with only Human living descendants. Set C: those with only Chimp/bonobo living descendants. Set B: those with Both human and chimp/bonobo living descendants. Set B is non-empty. For suppose otherwise. Then we would have no genetic connection between sets H and C except possibly crosses between them that fell into set O, and so were biological dead-ends. Sets H and C would then be in effect two separate clades running in parallel. But by definition Z contains the common ancestral group of H and C, so this is not possible. So B has some members. Not every member of set B can have descendants in B, because there is no-one alive today who is a member of set B. So there must be at least one member of B none of whose descendants are in B. Pick any such member of B and call this member B*. But there are only two ways to be in set B. One is to have a descendant in set B --- which B* does not do by definition --- and the other is for B* to have at least one child in H and one in C. This completes the proof. --- Note that there is no proof or claim of uniqueness of B* and no biological grounds on which we should expect it. But there must be at least one. --- I thought I had a rigorous proof of my original claim, but it keeps slipping through my fingers at present. In order to get at it this way I should have to show that the children of B* (call them H* and C*) were common ancestors of all living humans and of all living chimps/bonobos respectively, and although this seems very likely, I don't know any more that it can be proved certain even given additional biological considerations such as Dollo's law. I shall have to think about this. Edited by Dr Adequate, : No reason given.
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Dr Jack Member Posts: 3514 From: Immigrant in the land of Deutsch Joined: Member Rating: 8.4 |
Cool, thanks.
Doesn't your stronger claim simply follow from the length of time? I mean the MRCA of humans lived ~3500 years ago - presumably the MRCA for chimps follows a similar time scale.
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Jon Inactive Member |
Response to diagram on common ancestry. Could you please now add in Australopithecus, Homo habilis, Homo Rudolfensis, Homo Erectus, Homo Ergaster, Homo Heidelbergensis, Homo Neanderthal, Homo Cro-magnom, woodland apes. and then modern humans. I don't think that'd be necessary for this discussion. It's well established that the critters you listed did not appear until long after the speciation events. (BTW: I'm also stumped on the woodland apes reference. I googled them, but the closest thing I could find to a mention was listed as being in a book about human violence.) Jon "Can we say the chair on the cat, for example? Or the basket in the person? No, we can't..." - Harriet J. Ottenheimer "Dim bulbs save on energy..." - jar
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Taq Member Posts: 10045 Joined: Member Rating: 5.3 |
Indeed, and it is the time aspect that confuses me. How far back do we go to look for a common ancestor? What is recent? Conceptually, we are looking for the most recent ancestor. In the case of humans and chimps, we are looking for the most recent interbreeding population that contained all of the ancestors of both living humans and living chimps. This is not to be confused with common ancestry of a single gene. I think this is where the confusion is occuring. It is very probable that the common ancestor of a shared chimp/human gene is much older than the members of the most recent common ancestral population.
What is the agreed-upon most recent common ancestor - using the term cautiously - for humans and chimpanzees? Without DNA from 5-7 million year old hominid fossils it is impossible to determine.
I've seen some names thrown around here, but maybe we can look at the features and characteristics of these ancestors and compare them to present humans and chimps and ancestral humans and chimps to see how the common ancestor relates to both modern populations and to the populations of its daughter species "shortly after the lineages diverged" (to use phrasing by PaulK). Then we are only looking at the species that contains the most synapomorphies which still does not guarantee direct ancestry to any living organism, human or chimp. DNA is the only way to establish direct ancestry.
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