Question about evolution, genetic bottlenecks, and inbreeding

Thankyou Stagemancer, your the first person to get meMy whole problem is I can not reconcile in my head the idea of one creature we are descended from, and at the same time is not responsible for the whole human race.Because if we are descended from one creature, then there is inbreeding involved.
I understand there are genes contributed from other individuals to the common ancestor lineage, I just need someone to draw a tree for me.It is a logical fallacy to say there is not one creature we are descended from, because if we go far back enough, it is one cell.. and if you go back 30 years it your grandad, only the numbers in the population that have the common ancestor change depending on how far back you go.So how is it, that every single chimp and human is descended from a single being, without the problem of inbreeding. All I need is a tree drawn to sort this out, its just wherever I look, I just get a clear cut split from chimps and humans, the trees are not detailed enough.Guys no offence, but I asked for people to answer who know what they are talking about. We are just authoring confusion now.Edited by harry, : No reason given.Edited by harry, : No reason given.Edited by harry, : Typos

It's not that there's a single individual that we are descended from. Harry, let's use you and I as an example. At some level, we are related. We may be 3rd, 12th, or even 50th cousins, but we are related to some degree. So, if we go back far enough, we can find at least one person who is in both of our family trees. However, this does not mean they were the only person to contribute to our individual gene pools. What it means it that we have 1 person who has contributed some DNA to both of us. So, if you do that for the whole human species, you can find 1 person who has contributed DNA to everyone alive. BUT, there is not necessarily an inbreeding problem, because billions of other people have contributed to the worldwide gene pool as well. Does that help?

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"There are three kinds of lies: lies, damned lies, and statistics."

It's not that there's a single individual that we are descended from.

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Harry, let's use you and I as an example. At some level, we are related. We may be 3rd, 12th, or even 50th cousins, but we are related to some degree. So, if we go back far enough, we can find at least one person who is in both of our family trees. However, this does not mean they were the only person to contribute to our individual gene pools. What it means it that we have 1 person who has contributed some DNA to both of us. So, if you do that for the whole human species, you can find 1 person who has contributed DNA to everyone alive. BUT, there is not necessarily an inbreeding problem, because billions of other people have contributed to the worldwide gene pool as well. Does that help?

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Ok, so say we go back 50 generationsSay this person related to both of us is our great*49 grandad.He is our most recent common ancestor because that is the first person WE BOTH come across when tracing our ancestory backwards.so that is MRCA and that is pretty clear in my mind.So he our common ancestor, so how come,lol...I just got it, this second. wonderful.Thankyou very muchP.S. Sorry I may have come across as being a bit blunt guys. I have been spending extended periods in christian forums of late. I set up a thread and just let them ask me what they dont understand about evolution. Quite a success actually considering what you would expect.Its just ofcourse you get the YEC come in and say things that just are not true. So I really did want to come here just for a respite from that and fill in some gaps in my own understanding.Edited by harry, : No reason given.

Cool, ain't it?

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Genesis 2
17 But of the ponderosa pine, thou shalt not eat of it; for in the day that thou shinniest thereof thou shalt sorely learn of thy nakedness.
18 And we all live happily ever after.

a couple people still thought a common ancestor reffered to a whole species. Edited by harry, : No reason given.

Yes, well, the term "common ancestor" is mostly used to talk about a species, the term "most recent common ancestor" often refers to a person. Is this confusing? Yes, but what can ya do. I should, however, also point out, that with each new generation, the fraction of the genome inherited by each person from the MRCA approaches zero. So, if you go back far enough, you actually WON'T be able to find an individual MRCA. Now, I don't know how many generations have occurred since the split between humans and chimpanzees, but I'd be willing to guess it's enough that we wouldn't find an individual MRCA. Therefore, it is probably more accurate to talk about the MRCA of chimps and humans as being at least a population. As for humans and great white sharks, for example, there's just no way that there is an individual who is the MRCA, so in that case you WOULD have to use a whole species as the MRCA.

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"There are three kinds of lies: lies, damned lies, and statistics."

This is basically genetic.A person will contribute 50% genes to their children, 25% to their grandchildren and so forth.However, say we both carry a gene for brown eyes. We can go back far enough and find a genetic common ancestor who has contributed brown eyes to both of us. So in the same way we can follow family lineage, we can follow genes. So if we can't find our one common ancestor in a species we can trace our genes back instead. So say, our brown eyes came from this population, our blonde hair came from this one etc.

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for example, there's just no way that there is an individual who is the MRC

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Ofcourse there is, it is just impossible to know what specific creature it is. It is simply the creature we meet first going backwards that is related to both sharks and humans.

Yes, you can find an individual MRCA for specific genes, this is true. What I meant was that there's probably no single MRCA that has contributed DNA to every living human and great white shark as there IS probably a single human who has contributed DNA to every living person.

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"There are three kinds of lies: lies, damned lies, and statistics."

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there's probably no single MRCA that has contributed DNA to every living human and great white shark as there IS probably a single human who has contributed DNA to every living person.

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Agreed

Let's take this the simple way.Common ancestor refers to a whole species or at least a population.Most recent common ancestor refers to a whole species, population, or individual.Don't get caught up with the idea that a whole species is derived from one single individual! While an individual may be responsible for a specific genetic trait for the entire human race, there were billions of others who contributed parts and pieces of other genetic traits.Here is a simple analogy (don't get caught up too much in the analogy!). My great great grandfather gave my great grandfather some genes. The number of genes that my great great grandfather contributed to my great father was smaller. The number of genes my father inherited from my great great grandfather was even smaller. I got from my great great grandfather an even smaller number of genes.My great great grandfather also had a daughter, Catherine. Catherine's daughter Julie inherited some genes from my great great grandfather. Julie's daughter Anne inherited an even less number of genes from my great great grandfather. Anne gave birth to June.Is it inbreeding if June and I got married and have kids? Did we both get all our genes from our great great grandfather? Answer that question and I think you should have a good understanding of what's going on here.

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Most recent common ancestor refers to a whole species, population, or individual.

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NO, it can only refer to ONE INDIVIDUAL or one paring of individuals if you are looking for both male and female.Look at it this way (say we are looking for male). If I ask you to tell me your most recent common ancestor with your brother/sister, there is no way that is going to be a group, it is your father, end of story.Your FIRST (HENCE MOST RECENT) common ancestor with your cousin, is your grandfather (or would it be your uncle? as staga pointed out its relation not descendancy, either way it does not matter), because he is related to both you and your cousin with genes.You may very will have more than one common ancestor with your cousin, but you only have ONE most recent.

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Common ancestor refers to a whole species or at least a population.

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CorrectEdited by harry, : No reason given.Edited by harry, : No reason given.

When I promoted this topic, my vision was that it was intended to discuss the "what ifs" of a very small species population. This could possibly but not necessarily be as small as only one male and one female. This could be from either the physical isolation of a small group away from the rest of the species, or the literal only the two of the species left on Earth.The Biblical parallel would be the "what if" the human species would have been just Adam and Eve. What would be the genetic chain of events of the ancestors of Adam and Eve be like?Or something like that.Adminnemooseus

I knew this was going to happen. I knew you'd take the analogy too seriously and treat it like the real thing. *sigh*Let me start this again. The most recent common ancestor can refer to either a population or individual, depending on what we are talking about. If we're talking about two distinct species, say chimp and human, the most recent common ancestor couldn't have possibly be one single individual. This is a ridiculous statement to make. Why? (1) individuals can't evolve. The smallest unit that can evolve is a population. (2) The combination of traits from many individuals contributed to the emergence of both species.On the other hand, it is also an obviously true statement that at some point in the past there was an individual that had at least 1 genetic trait that now exists in both species.One could even argue that this is all semantics. I know I am correct. I think I'll play dumb for a little bit. First, you disagreed with me. Then you said I was correct. I think you have an integrity issue here. I think you are caught in a web of lies that you've resorted to contradicting yourself. Do you lie often?

Think of a speciation event. A subpopulation is separated from the main population so that there is no gene flow. This daughter population carries a subset of the larger populations gene pool, will have unique mutations occuring within its population, and may experience different environmental pressures. Over many generations this daughter population becomes sufficiently different from the parent population that interbreeding cannot occur and they are regarded as a new species.
Now in this scenario, you will note it is the population that has become the new species over time, you can't point to an individual that is the new species. So how would you point to an individual that is the common ancestor? All the breeding individuals in the daughter population have contributed to this speciation event.

Not at all. Consider the following picture ... I'm not sure for what technical reasons it comes out looking so odd, I think it presupposes a white background. Individuals A - H all have the status of MRCA of the group consisting of the group consisting of S, T, U, V, W, X, Y and Z.H is Mitochondrial Eve.The image is taken from the SkepticWiki article on Mitochondrial Eve, which you might want to read.