Rational BAC

I still think that "life will out". Even though the survival rate at first might be pitiful.

And remember that we have modern medicine and modern ideas of morality (all life is sacred, protect the weak among us etc.) to keep the inbred 'defectives' alive. -------all of which would not be true in a primitive society. No modern medicine, no ideas of morality except for the survival of the 'tribe'=====the recessive genes would die out--only the strong would survive.

I still think the analogy with the overuse of antibiotics creating "super germs" is not a perfect analogy but is still a valid one..

The idea being --------try to kill off everything. Kill them all--you got it made. Let one out of 100 or one out of 1000 survive, and you have left a tough little bastard life form to reproduce itself.

I think that is just as true for humans as it is for microbes. (Except, of course, for the fact that you are dealing with much larger numbers with microbes. )

Any dispute on this?

Rational BAC

Let's take a hypothetical----

An evolutionary Adam and Eve.

Eve was the mother of all mothers. Popped out babies like they were going out of style (which they were I guess--all we got left genetically is the "Eve" from Africa). Started at 13, ended at menopause at 55-------had 40 plus kids.

Now assume Adam and Eve were isolated for some reason. The brothers and sisters did what comes naturally. The mom and dad, being the primitives they were, also did what came naturally.

And in the next generation, due to all that inbreeding, all hell broke loose. Lost maybe 90%. But 10% did survive. And they interbred. And many of the females had that baby producing thing Mom had------(babies every year with no birth complications causing death) Maybe 20% survived. And on and on. --------to the 4? 6? billion people we have on Earth today.----------and damn it all we still have those recessive killer genes that still pop up from time to time.

Doubting Didymus

Well, when Thomas Austin in 1859 introduced rabbits to Australia, their number was a mere 24. It's true that there were already some rabbits present in the country, but Austins bunnes are almost certainly responsible for the subsequent population explosion. I think that if we managed to curb the current plague back down to 24 we'd be just as screwed again in 10 years time.

Rational BAC

Another puzzle----

As far as I understand it, all humanity came from the "Eve" from Africa (whether Eve was one woman or 250 is irrelevent for this part).

Why?

What happened to all the other "Eves"? The world is an awful big place.

(And not to confuse things too much, but supposedly our genetic "Adam" happened 70,000 years after our genetic "Eve".)

Too much for this poor brain. Somebody explain this part.

Skydancer

The quick and dirty version is : Males inherit y-chromosome material only from their fathers, and everyone inherits their mitochondria only from their mothers. If you trace back your mother to her mother to her mother, etc, it turns out that all the female lines converge on one individual at some point in time. If you trace a male's inherited y-chromosomes to his father, to his father, etc, you hit an ultimate shared male ancestor at some point as well.

The two convergence points are independent, because during the life-time of Eve or Adam, there are plenty of other humans alive - but all the other women alive during Eve's lifetime had only male descendants living at some point, and all the other men alive during Adam's lifetime had only female descendants alive at some point.

Rational BAC

I think I understood the first part fairly well. But don't you think the last part is --at best-- a little far fetched?

For what possible reason would there at one time be only male descendents and at another time only female descendents? Odds against this birth-wise are absurd.

You are talking about some kind of very odd social phenomenon causing this very strange occurance?

Doubting Didymus

Its not so much that there are miraculously only females born to eves contemporaries, but that all direct female lineages other than eves eventually ended. They could have continued for any length of time after eves existance.

Peez

It wouldn't. Inbreeding can be a problem, but certainly does not guarantee the extinction of a species.Excellent logic. In fact inbreeding has the effect of getting a lot of recessive genes expressed, and therefore exposes them to natural selection (for good or ill). There are populations of organisms that are routinely inbred, but because of this they tend to have very few dangerous recessive genes. Thus for them inbreeding is not generally a problem. It is generally a problem for outbred populations that are suddenly faced with inbreeding, as they have accumulated plenty of nasty recessive genes.Perhaps the term "speculate" would be better than "theorize" in this context.It doesn't generally, but it can certainly make a population more prone to extinction.[quote]I suspect, all theories aside, that "life will out" (or maybe it was "life will find a way"---from that dinosaur movie) no matter if that life started with brother/sister incest. And therefore Genesis is technically possible and an actual evolutionary "Adam and Eve" is even more possible.[/blockquote]Inbreeding could still have been a problem with the Adam and Eve story, but it does not disprove it. The fact that is inconsistent with that story is the great variance in genes that are found today. A few thousand years are not sufficient to generate that much genetic variation from two individuals (even if they had as many different genes as possible).I am not familiar with that claim.I have tried to clarify, let me know if it is still unclear.

Peez

Peez

Excellent question! The answer is that yes, it would, but it would tend to make no difference. For example, if gene A on one chromosome is passed to its homologous chromosome, and in return gene A is passed back, nothing has changed. That being said, crossing over can sometimes result in changes to genes (this would qualify as a kind of mutation).That is essentially correct, but the linkage is not absolute.
Closely-linked genes would tend to be inherited together, but eventually we would expect them to be separated by crossing over. Certainly the rate at which new genetic variation would have to be generated to get the variance we see today from one small family alive about 4,000 years ago is much higher than seems possible. Note that it is really Noah's family that is the issue here.

Peez

Wounded King

There was a recent paper in 'Evolution' about recovery from a large deleterious mutation burden in C. elegans. It isn't quite what you were asking about BAC as the recovery was measured in an effectively outbreeding population of previously inbred organisms.