I know we have done that specific topic here a number of times over the years, and I think as recently as within the last year, but my best search-foo couldn’t find the thread(s).
Maybe someone else can dig the most recent one up?
I’ve never heard that, but Genesis 5:4 explicitly states that Adam had other sons and daughters (presumably with Eve).
There’s also the question of the mysterious Nephilim, the “sons of God” who mated with “daughters of men,” and how they fit into human genealogy.
I went to the Creationist Museum on a road trip, and their answer for the incest thing was that God hadn’t said incest was wrong yet, so it wasn’t wrong at the time.
There is no reason to presuppose that such a pattern would result in a race of genetically identical people. Not without presupposing that Adam and Eve were genetically identical and homozygous for every trait. In a cross of pure bred lines the F[sub]1[/sub] generation may be identical but the F[sub]2[/sub] and subsequent generations show tremendous variety in genotype and phenotype.
Inbreeding promotes homozygosity and reduces heterozygosity. That results in an increase in the expression of deleterious recessive phenotypes. But it also eliminates deleterious alleles which might have been carried by heterozygotes who would have been silent carriers of such a deleterious recessive trait. (And not all recessive traits are deleterious)
The genetics of the immune system and how the body generate antibodies is fascinating… and truly seems to defy some common understanding about genetics. DNA is rearranged in the process of B cell development allowing to the potential production of some 10[sup]12[/sup] possible antibodies from a relative small number of genes. In short, genetically identical people do not generate the same antibodies and do not have, in any meaningful way, the same immune system.
Yes there is, because that’s what extreme population bottlenecks tend to produce. That’s why I brought up cheetahs as an example; they are so genetically and immunologically similar that skin transplants can be performed between random individuals without rejection.
That’s more less what I was told by a very annoyed Sunday school teacher. She also said that all those generations of inbreeding drastically shortened the human lifespan which is why modern people don’t live 900+ yrs like the Biblical Patriarchs.
You are showing a fundamental failure to understand the genetics of antibody production. Did you not read the cite from my prior post?
Your argument would be like expecting all rolls of a two pair of dice to be identical because they came from the same mold. But the results of a series of rolls would not be the same. There is a randomization event.
During the maturation process of a B cell (a cell critical in the immune response) there is a random cleaving and joining of DNA involved in the production of antibodies. Identical twins thus end up with quite different genetic sequences in that part of the genome in their mature B cells.
If we did not have that process then each possible antibody would need to be coded by a separate gene - an unwieldy burden on the genome.
And since genes of the HLA system are some of the fastest evolving genes, after a period of time following any genetic bottleneck there would be increasing diversity of allele variation in those loci as compared to other loci.
Iggy: you aren’t making yourself clear, at least to me. I have heard the same things that Der Trihs is citing. Cheetahs can receive skin transplants from each other without rejection: they resemble one enough genetically to that degree, because they went through a reproductive bottleneck. Scientific American had an article on American corn (maize) pointing out the same thing: those vast Kansas fields have very little genetic diversity, and are thus susceptible to a plague.
If inbreeding and genetic drift and so on are not real, you need to explain your point a bit more clearly.
Is your argument merely with Der Trihs’ use of the phrase “genetically identical?” If so, shrug: it was a loose phrase, not intended (I think) to be taken literally. Of course there would be some variation within this tiny population. Just not much – and probably not enough to allow for species survival.
As for where Cain got his wife, never overlook the compromise theory promoted by Tom Weller in “Science Made Stupid.” Adam and Eve were created, but the tribes from which Cain took his wife evolved. Obviously a theory that should be taught in schools, as it will be perfectly satisfactory to all viewpoints and beliefs!
Maize and wheat are a poor comparisons as plants do not produce antibodies and do not have adaptive immune systems. Humans do. And it makes all the difference.
Genetic dogma long considered that one gene coded ultimately for one protein. Further study and investigation showed this is not entirely the case, particularly in the immune system.
V(D)J recombination is a process that randomizes part of the genetic code involved in antibody production. This process makes permanent changes in the genetic code of a developing B cell. These changes are passed down to daughter cells.
Those B cell which successfully bind to an antigen are chemically stimulated to reproduce. Some of those daughter cells are preserved as memory B cells. That is what allows your immune system to recognize and quickly respond to a second exposure to a particular pathogen.
As a result, there is a sort of evolution and natural selection on a cell-by-cell basis within an individual. Those B cells which are “successful” are stimulated to reproduce and are preserved. This makes for a robust and (from a genetic point of view) efficient production of a wide variety of antibodies from a limited number of genes.
Suppose there was not such a system of randomization. A genetically similar population would be highly susceptible to attack by the same pathogen. If an individual did not happen to have the version of a gene that coded for a particular antibody that was capable of successfully binding to an antigen on the pathogen then the individual would be out of luck.
But the reality is there is a highly variable and efficient adaptive immune response that allows for production of millions of different possible antibodies within an individual. This means that individuals who are substantially genetically similar (e.g. identical twins) are capable of producing very diverse and different immune responses to a new pathogen. This diversity of possible immune responses helps protect a genetically bottle-necked population from being completely wiped out by a new pathogen.
Okay, good… And some of that matches stuff I’ve heard elsewhere, so we don’t have to get bogged down in citing and refutation of sources.
So, let’s say that Der Trihs and I were wrong in considering weakness of the immune system to be a drawback of a very small population base.
We still have the genetic drift problem, concentration of recessives, and other messy problems. A population of humans, beginning with only two, could not last very long.
Long ago I attended a church that believed (though did not teach dogmatically) that Adam wasn’t the first human being, but was a specially-created human being intended to be somehow better than all the already-existing humans. I forget what they based this on, but somewhere in the creation account IIRC there’s a spot where you might naturally think two events happened one right after the other but this church thought it possible to read it as instead involving a time gap of many millenia.
So Cain’s wife was one of those other humans, not a descendant of Adam.
Oh yes, I remember now–it was between verses 1 and 2 of chapter one of Genesis. In the beginning, God created the heavens and the earth. (And then a bunch of stuff happened and eventually the earth had some real bad stuff happen to it) and the earth was without form and void. (Then God started fixing it all up and made a new kind of human being.)
Genetic drift is a problem. Humans just are not capable of producing enough offspring to get around that problem.
Concentration of recessives may actually not be such a problem. Set aside the ‘ick factor’ about inbreeding for a moment.
Inbreeding increases the chance of getting two copies of the same form of a gene (being homozygous for a trait) and decreases the chance of having different copies (being heterozygous).
If there is no particular survival advantage of one version over the other then it does not matter so much.
If there is a selective advantage of one version of the gene over the other then inbreeding will produce an excess of individuals exhibiting the deleterious trait. Natural selection acts against those individuals. And IF (<– note big IF) there are enough individuals in the population to survive the loss of a few, then the recessive trait is pushed to elimination faster in an inbreeding population than in a randomly breeding population.
If the deleterious trait is recessive then the push to purge that allele from the gene pool can be quite slow, but is still faster in an inbreeding population. If the deleterious trait is dominant then the push to purge that trait can be quite strong and rapid regardless of whether the population is randomly breeding or inbreeding.
Now… to put that line of reasoning in modern terms. In many societies there is a taboo against inbreeding. And so populations are not randomly breeding - they are outbreeding (disproportionately favoring unrelated partners). Such a pattern of breeding results in a rise in heterozygotes and a reduction in homozygotes. This allows for deleterious recessive alleles to increase in frequency and ultimately results in a higher prevalence of recessive genetic diseases.
Well… it depends on what animals you’re talking about. There are several bird species that have been down to insanely low numbers- the Chatham Island Robin got down to 5 individuals, including only one fertile female, and it’s thought that all 250 existing robins are decended from just one pair, and the 800 or so Mauritius Kestrels are all decended from just two pairs.
Interestingly, neither species is showing any signs of inbreeding problems.
ignore this post–misread a previous post.
Eeeww!
The nuns in my Catholic grade school taught us that Adam and Eve weren’t just two people, but a whole “group of people.” They said it must have been a group so that Cain & Abel could find wives who weren’t their immediate relatives.
I can report this is what was taught to me during my Southern Baptist by the grace of og upbringing. No rule against incest until Leviticus, so whatcha gonna do when god tells you to be fruitful and multiply? Your sister, that’s what you’re gonna do.
Bible ‘scholars’ estimate 28 boys and 23 girls for Adam and Eve, IIRC. No cite, but I think Answers in Genesis will back me with similar numbers.
I knew someone would get nitpicky on that. I used “blood related” to distinguish between Noah and his sons, which are directly related, and Noah and his sons wives who only have some common ancestors.
The point was that the concerns with Adam and Eve are not the same as with Noah. Noah is not dealing with any immediate incest. So it doesn’t matter that his genes aren’t perfect. They aren’t the only ones being used.
I think the poster I was responding to forgot that the wives came from before the flood.
That’s similar but not quite the same as a theory I’ve heard. Adam and Eve were still two individuals, but they just weren’t the only humans created by God. They just are the only ones the Bible follows.
Yeah, either of the two scenarios is way better than attributing incest to the mandate of Jehovah. Again—eeewww. How could anyone be so blockheadedly literalist as to come up with that?