Question about evolution, genetic bottlenecks, and inbreeding

HiI am a evolution enthusiast but I am struggling with one of the concepts.When a species is isolated, goes through a bottle neck, or a small amount of one species is divided from the rest and branches into a new species, what prevents inbreeding having to much of a negative impact to the species survival?Surely the time it takes variety in the smaller gene pool takes longer than it would for inbreeding to have an effect.Educated researched answers please! No nonsense about this is a disproof of evolution, or half baked answers please!!Edited by Adminnemooseus, : Added the ", genetic bottlenecks, " to topic title

Ok, so I kinda knew that.So, I am struggling to wrap my head fully around common ancestor and how that ties in with inbreeding.So one little monkey, has fun time with another monkey, and they have 2 baby monkies, monkey one goes on to become humans, the other goes onto become chimpanzees.So monkey 1 is our concestor with chimps. however, even if monkey 1, were to mate with 5 females, the grandchildren would all be very inbred.Can somebody draw me a tree of how 1 ancestor gets enough genetic material to mix it up? Because surely it can't get that many from the species it split with, or it would not be the common ancestor, and the whole process would start again.Thanks for the welcome!

I got the impression from the text books that a common ancestor was an individual.

I see, I have been getting common ancestor confused with Most recent common ancestor.Thanks for the help guys!

quote:

---

That's a mistaken impression. As I said, evolution happens over populations, not individuals. It's an incredibly slow process that happens by increments of mutations - Species X does not give birth to Species Y. Species Y is a descendant of Species X only after many generations of mutations sufficient to disallow interbreeding between the two.

---

Yeah I am way beyond that levelSo there is a difference between most recent common ancestor, which is an individual, and a common ancestor?

No that is wrong, the MRCA is not a species, I know that for sure.Unless there is any confusion.All humans have a MRCA, we all related through one individual.So therefore there must be an individual from which all humans and chimpanzees are descended, regardless of whether that individual bred with with how ever many other monkeys.Edited by harry, : No reason given.

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.

quote:

---

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?

---

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.

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

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.

quote:

---

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

---

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.

quote:

---

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.

---

Agreed

quote:

---

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

---

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.

quote:

---

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

---

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

So why is H eve and not F? She also seems to be related to everyone.Edited by harry, : No reason given.

Ok I go, that, but then in there is a Y - adam, person A.He is the MRCA.So therefore, A is the male MRCA, H is the female.All the others are common ancestors but not most recent. To the whole population.A pretty rubbishy source but a quick google search reveals
Page not found - Tripatlas'Y-chromosomal Adam' ('Y-mrca')Wikipedia:most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descendedThe two evolution books I have on the topic also refer to the MRCA as one distinct individual.We are beyond my question now. I understand fully how one MRCA can exist without the problem of inbreeding, as the mitrochondiral eve graph represents. However, it is innapropiate to use the same graph to say 'they are all the MOST recent common ancestor. All, common, sure, not most recent.Can anyone quote a peer reviewed source to tell me this is wrong? It is the only conclusion I can seem to get, and staga seemed to agree.Edited by harry, : No reason given.

Yes I do agree, but if one is the Y-adam it elevates him to the position of MRCA.Like I said, you can say that, but I am talking about a definition, an important one. It isn't semantics, because these defintions can not be confused, and I am still confused.I am asserting that Y-adam is the MRCA because that is what I have seen so far. You have all talked the talk, but you are not saying, look at this, according to this defintion, All of these people are MRCA, you have just pointed to a graaph, with an explanation of a relevant, but different topic on mitrochondrial eve.You have basically posted a graph and said 'by my definition all these people are the MRCA.'by my defintion it is Y-adam.Who is right? IF you can show me I am wrong with a good reference, I will believe you.

quote:

---

Each of the ancestors A-H are equally far from the offspring at the end, therefor they're equally recent.

---

You need to back it up with a reasonEdited by harry, : No reason given.Edited by harry, : No reason given.