Any Geneticists out there?

The Open Forum has a thread going about Noah's Ark, and I posed the question  "how is it possible from just 7-8 brothers & their wives,  to evolve the following pure racial groups: Negro, Asian, Indian, Anglo-Saxon & Australian Aboriginal"?

This is the question I am hoping will be answered by someone with a good understanding of human genetics.

By the way, I learned a new word - the 'Mulatto' person, [having mixed ancestry] as a possibility for generating the above racial groups.

This suggestion seems to me a bit similar to turning white light into its component colours, not by filtering through a prism, but by adding another beam of white light!?

You don't need to be a geneticist to understand that the literal interpretation of Noah's  Ark is absurd. Although if you have REAL questions about genetics, I'd be happy to help. I am not a geneticist but I've studied genetics

It's impossible to generate those different races with so few people, and that's a fact.

Any adaptation is possible on a long enough time scale. I wouldn't say it's impossible at all, given that the initial interbreeding didn't weaken any genes neccesary for survival.

The question itself has some problems, aside from the assumption that the story of Noah and the flood was literally accurate.  For one, the question suggests that there are such things as "pure racial groups."  People within a particular racial or ethnic group still exhibit a large degree of genetic heterogeneity.  The extent to which genetic differences exist between different racial groups is still being studied, but it is widely accepted by geneticists that there is no gene or set of genes (or rather, I should say "no allele or set of alleles") that makes a person belong to a particular race.  There are alleles (i.e., variants of particular genes) that are more prevalent in some races than in others.  However, that does not mean that if you possess such an allele, you automatically belong to a particular race (or conversely, that if you lack such an allele, that you do not belong to a particular race).  Also, different racial groups are not analogous to different colors of light, as suggested in the original comment.

However, the question does make some sense (not to belittle the quality of Cret1n's question).  One could ask how a small number of initial humans (or a small founder population after a cataclysmic event) could eventually give rise to large groups of humans with distinct features.  This can happen through the processes of macroevolution.  I'm going to try to be as succinct as I can while still giving you a good idea of the processes involved.  The initial population already possesses some genetic heterogeneity.  Some people have some alleles that are different from those of others in the group.  As the population grows due to mating, mutations can introduce new alleles into the gene pool that were not previously present in the population.  Some alleles will become more frequent or less frequent because they allow the individuals possessing them to be more able or less able, respectively, to survive and reproduce.  This is called natural selection.  Some alleles will also become less frequent or more frequent in the population over time, simply due to random events.  This is called "genetic drift."

Over time, the population could split up into different, geographically isolated groups.  The different groups may, simply due to chance, have different allele frequencies at the time they split up.  On top of that, these groups could also eventually be exposed to different environmental conditions, and so natural selection would favor some alleles in some groups, but different alleles in other groups.  Some alleles may also become more frequent in one group than in another due to genetic drift.  New mutations may introduce different mutations into different groups.  Repeat this process for thousands of generations, and allow the human population to expand across the face of the earth, and viola!  You wind up with many groups of people that possess features that are different from groups in other locations.  On a smaller scale, this is what happened with the finches that Darwin studied in the Galapagos Islands.

I hope that is a satisfactory answer to your question, and I apologize if it was too long.

allopatric speciation.

Thank you all for your input - especially posts 5 & 6. I was under the impression that DNA would reveal something as obvious as racial background...but apparently not. This impression lead me to hypothesize that the gene pool aboard the Ark was just too small to give rise to such deviation in eye shape, skin / eye / hair colour, muscle distribution or skull shape for example.

What I am after is a person qualified in the biological sciences [plz state your qualification] who can point out why it is impossible [or possible!!] for a small gene pool such as that allegedly aboard the Ark to evolve into the racial groups we observe today. Remember the time frame...only 4-5000 years! Also, the distances these brothers & wives had to travel to distribute their genes seems a bit optimistic to me.

Given we start with a bunch of brothers [& their wives] can anyone seriously tell me that if each brother migrated to a particular part of the world [I know it becomes ridiculous but I'm not supposed to state controversial opinions outside the open forum - which is where you guys should belong!] we could end up with the diversity we see today!

P.S  This is not the place to attack any religious text...join the open forum for that!

The time frame is not possible.  All human races did emerge from a small population that emigrated from Africa but that was a very long time ago.  Four to five thousand years is simply recent history. Sorry to say it but some texts are just myths.

I really don't think the bible should ever be taken literally. How would the people know that any flood was global? Picture yourself on a boat in the middle of any decent sized body of water. Lets say you can see 20km before the curvature of the earth means you can't see any further. You are then able to see something like 0.00025% of the earths surface. You would have absolutely no way of knowing what was happening on the rest of the surface.

of course all those races can come from so few people.  How do you think the races evolved wether from the time of Noah's ark or before the races evolved from only a few, so starting from "scratch" really doesn't matter because it happened one time or another in THE SAME WAY.

The problem is timescales. Mapping Mitochondrial DNA from fossils traces humans to Australia and Northern Europe something like 65000 years ago, Asia 40000 years ago and America 10000 years ago. Studies of DNA have also identified Genetic bottlenecks where large portions of the Gene pool died out, for instance around 70000 years ago when the supereruption of Toba occurred but there is no proof of such a global bottleneck 5000 years ago.

Ok. Having checked LucidDreamer's profile I find he is exactly the guy I am looking for. It just shows you LD, how much misunderstanding the general populace must have on your special subject.

Can I ask a similar question! We both agree that Noah's Ark is just myth, but let's assume it happened [just as a thought experiment]

There are no other humans on planet earth except for those 7 pairs of people, all of similar racial stock ["Arabic" I guess - & I take your point about homogeniety. We could try the same experiment with modern day Chinese if you like]

If these pairs have offspring, which in turn breed only with each other from the same "Arabic" or "Chinese" or "whatever" racial group [remembering this is the only set of humans with which to breed] would you say that the offspring would be able to evolve into the various racial groups we see today? How long did such differences take to evolve?

I thought dark hair & dark eyes are examples of "dominant genes" [trying to remember my high school biology] and would never give rise to a mass of blue eyed blond people. Perhaps you can comment on the causality of the different physical appearance of the Scandinavian & say Chinese groups?

Hi Cret1n,

This is an interesting thought experiment, and I will respond to it as soon as I can.  Unfortunately, I am in the midst of preparing for my PhD qualifying exam, so I will not be able to give you a proper response today.  Perhaps tomorrow or the day after.  However, in brief, I would assert that the offspring would be able to evolve into the various racial groups that we see today, but I can't tell how much time would be required for such differences to evolve.  Perhaps if I think about it some more, and perhaps do some reading, I can give you a better response regarding that aspect of your question.  I'll also give you more details as to why it would be possible for such a small group of closely related people to give rise to various racial groups with different traits such as eye color and skin color, and our current knowledge regarding how certain traits popped up in the real human population.  However, it essentially boils down to the processes I mentioned before:  mutation, migration/isolation, natural selection, and genetic drift.  I look forward to talking to you later!

I should also say that even though I can't give you an estimate as to how much time would be necessary (at the moment), I am certain that 6,000 years would be woefully insufficient.  I'm going to try to estimate what the germline (i.e., heritable) mutation rate would need to be in order to produce the amount of genetic variation we see today in that timeframe, and see how that compares with observed germline mutation rates.

Cretin

You have it backwards.  Dominant genes mask recessive ones which can recombine with other recessive genes from a similar mate.  Recessive genes mask nothing and can therefore not give rise to other forms.  That is dominant forms such as dark eyes and dark hair can produce offspring with blond hair and blue eyes.

take this back to the OPEN DISCUSSION group.