Question about Inbreeding

[Chattiestspike2]

Is it true that if the human race theoretically started with two individuals with ideal genes and no detrimental traits, that their offspring and descendants would be perfectly fine even though they are inbreeding? If so, should inbreeding really be considered a problem with Adam and Eve since they theoretically started out with "ideal DNA?"

 

[Unwardil]

Ideal DNA is just as fictitious as Adam and Eve themselves. Quite simply put, that's not how DNA works. It's a means of self replicating memory storage. You might as well say you have the perfect information on your hard drive. It's an equally absurd thing to say.

 

[Aught3]

No problems from inbreeding but they wouldn't evolve.

 

[Chattiestspike2]

Ideal DNA is just as fictitious as Adam and Eve themselves. Quite simply put, that's not how DNA works. It's a means of self replicating memory storage. You might as well say you have the perfect information on your hard drive. It's an equally absurd thing to say.

If you give them the benefit of the doubt on this: Adam and Eve didn't have any detrimental traits. No susceptibility to any sicknesses, diseases, or anything like that. Great immune system that happens to be there even though there isn't anything in existence to be immune to yet. They can sing, both are fertile, perfect vision, perfect hearing, etc. Fine there is no such thing as PERFECT dna but how about just REALLY good traits and nothing detrimental. Would inbreeding still cause some major damage down the line? Or is inbreeding a bad argument against the Adam and Eve myth?

 

[Unwardil]

So what is a 'good' trait?

Name absolutely any possible trait that an organism can posses and I can tell you how, depending on the circumstances it will either be beneficial or detrimental. Genetic traits can only be understood in relationship to the environment in which you find the organism which possess said traits.

Who will win in a fight, a naked human or a naked grizzly bear?

Who will win in a math competition?

Which can better survive the vacuum of space?

Further more, traits which benefit one area will be detrimental to another. So humans have very advanced brains. This means that we spend a very long time developing from infancy to adulthood when we become able to reproduce. Let's say solar activity increases and floods the earth with radiation, decreasing the average life expectancy to around 4 years old. Oh damn, our big brains have killed us off.

That is why your question doesn't make sense.

 

[Aught3]

Okay OP, I'm not sure your clear on why inbreeding depression occurs. Most genes that produce a disease phenotype (e.g. haemophilia, cystic fibrosis, and Tay-Sachs) are recessive which means you need to inherit two copies of the gene to get the disease. If you only have one copy of the gene you are a carrier but the dominant version of the gene can compensate for the deficiency which means your fitness is not effective. On very rare occasions two carriers will meet and give the disease to approximately 25% of their offspring. However, when the individuals are genetically related, there is a much greater chance that they will carry the same recessive genetic mutation and therefore a greater chance that they will produce a disease phenotype in their offspring.

 

[Unwardil]

Not what I'm talking about.

I wasn't even bothering to address inbreeding because the idea of a genetically perfect individual is absurd.

Even if you have two dominant chromosomes, it's still only one of them that activates because, in actuality, every chromosome is just a tiny bit different due to copying errors. Error correction algorithms in DNA smooth this out, but it still remains that even in two nearly identical genes, you've still got a dominant and a recessive among them.

And what about conditions which require a certain combination of dominant and recessive genes, the same way that some electrical circuits actually require inactive pathways. The point is, there is no 'Good' and 'Bad' DNA or genes, so you cannot have a genetically perfect being.

Even if you could, you'd still get mutation during reproduction.

 

[Aught3]

Not what I'm talking about.

Well I was addressing the OP. Sorry, I didn't make that clear.

Even if you have two dominant chromosomes, it's still only one of them that activates because, in actuality, every chromosome is just a tiny bit different due to copying errors. Error correction algorithms in DNA smooth this out, but it still remains that even in two nearly identical genes, you've still got a dominant and a recessive among them.

That's not quite correct. The alleles may be slightly different but both of them will still be expressed. What happens in the case of a recessive gene is that it is expressed but the gene product doesn't work.

 

[Chattiestspike2]

Ok my point was this:

Is inbreeding really that much of a deadly problem with the hypothetical Adam and Eve? When arguing against the Adam and Eve thing, is inbreeding a good argument or not? =P

 

[Aught3]

Ok my point was this:

Is inbreeding really that much of a deadly problem with the hypothetical Adam and Eve? When arguing against the Adam and Eve thing, is inbreeding a good argument or not? =P

If your hypothetical Adam and Eve have no detrimental traits then I would say inbreeding is not a deadly problem. As they start to have offspring there will be errors that creep in and then inbreeding would have a detrimental effect.

As a side-note I thought that most people brought up the inbreeding argument just to gross-out the Christian :lol:

 

[Unwardil]

The main reason that it wouldn't be a problem with the hypothetical Adam and Eve is that those hypothetical people would have been brought fresh into existence, meaning that no natural parasites would have had a chance to evolve along side them. Most viral or bacterial pathogens are highly specialized and are only able to infect certain species. If a completely new species with completely new DNA were to be created tomorrow, it would be immune to pretty much everything.

Inbreeding is generally pretty safe for a single generation between any two people come to that though, it's just you don't want to make a habit of it, but say in a post apocalyptic society, it wouldn't be a bad idea for siblings to breed. It WOULD be a very bad idea for them to breed exclusively. You'd want to be polygamous as possible.

 

[Nautyskin]

So what is a 'good' trait?

Name absolutely any possible trait that an organism can posses and I can tell you how, depending on the circumstances it will either be beneficial or detrimental. Genetic traits can only be understood in relationship to the environment in which you find the organism which possess said traits.

Spot on.

/thread

 

[Anachronous Rex]

If you want to see what a highly inbred species looks like, look to cheetahs:
http://news.worldwild.org/cheetahs-plight/

The lowest number I've seen for modern cheetahs' bottleneck population was 6-10, and this has rendered them exceedingly vulnerable; if it were two... well, I imagine they'd be extinct.

Hell, humans suffer from a low genetic diversity that renders us relatively vulnerable, and estimates for our bottleneck population is speculated to be somewhere in the neighborhood of 7000-10,000.

 

[Skillbus]

The two people would have to not only have good genes which led to their phenotypes, but also good inactive recessive genes. The problem with inbreeding is that it can lead to rare, harmful, recessive genes getting paired with themselves. And yes they would evolve. Their descendants would just have to accumulate a lot of mutations first.

 

[Skillbus]

Ok my point was this:

Is inbreeding really that much of a deadly problem with the hypothetical Adam and Eve? When arguing against the Adam and Eve thing, is inbreeding a good argument or not? =P

If your hypothetical Adam and Eve have no detrimental traits then I would say inbreeding is not a deadly problem. As they start to have offspring there will be errors that creep in and then inbreeding would have a detrimental effect.

As a side-note I thought that most people brought up the inbreeding argument just to gross-out the Christian :lol:

Really, you don't think the fact that they were inbreeding all the time would lead to any possible fresh mutations for harmful recessive genes being paired with themselves and thus selected against, making inbreeding safe?

 

[Aught3]

Really, you don't think the fact that they were inbreeding all the time would lead to any possible fresh mutations for harmful recessive genes being paired with themselves and thus selected against, making inbreeding safe?

Well certainly not safe for the individuals that end up with the deleterious phenotype. Inbreeding depression is not a forgone conclusion but it is a real effect that does happen in isolated human populations. If the inbreeding is severe enough the dominant allele can be lost from the population leaving only individuals displaying the undesirable trait. That would certainly be a realistic possibility of sustained inbreeding.

 

[Giliell]

Really, you don't think the fact that they were inbreeding all the time would lead to any possible fresh mutations for harmful recessive genes being paired with themselves and thus selected against, making inbreeding safe?

Well certainly not safe for the individuals that end up with the deleterious phenotype. Inbreeding depression is not a forgone conclusion but it is a real effect that does happen in isolated human populations. If the inbreeding is severe enough the dominant allele can be lost from the population leaving only individuals displaying the undesirable trait. That would certainly be a realistic possibility of sustained inbreeding.

It also would make that population rather unsuccesfull at reproducing, especially in a species with so few offspring compared to other species.
Even without sever genetic problems, the infant mortility in non-industrialized human societies is pretty high, as well as the mortality of mothers. If now 25-50% of the offspring are doomed due to genetic problems, we might not be able to reproduce enough to keep the population stable. And recessive genes can "sleep" for generations in the maternal line. I know that I have a "bad" X-chromosome for colourblindness from my dad. I don't know whether my daughters still have it. Could appear in generations to come when nobody even remembers the odd ancestor who wasn't allowed to dress all by himself if the occasion was festive. So, with enough "bad chromosomes" around, youwould face the same problem every and every generation.

 

[Ilikemustard]

Most viral or bacterial pathogens are highly specialized and are only able to infect certain species. If a completely new species with completely new DNA were to be created tomorrow, it would be immune to pretty much everything.

Does this mean that the ending in "The War of the Worlds", in which the invading aliens die due to having no immunity to viruses on earth, is incorrect?

The lowest number I've seen for modern cheetahs' bottleneck population was 6-10, and this has rendered them exceedingly vulnerable

That's quite amazing, to think that at one point cheetahs were at the very brink of extinction, but somehow managed to regain numbers.

 

[Anachronous Rex]

Most viral or bacterial pathogens are highly specialized and are only able to infect certain species. If a completely new species with completely new DNA were to be created tomorrow, it would be immune to pretty much everything.

Does this mean that the ending in "The War of the Worlds", in which the invading aliens die due to having no immunity to viruses on earth, is incorrect?

Viruses yes, but sadly not bacteria... which would set upon your virgin immune system like a horde of locusts, and kill you in ways you can't even begin to imagine.

The lowest number I've seen for modern cheetahs' bottleneck population was 6-10, and this has rendered them exceedingly vulnerable

That's quite amazing, to think that at one point cheetahs were at the very brink of extinction, but somehow managed to regain numbers.

It indeed is, and may in fact be the reason they're so specialized (natural selection works better on small populations.) Another cool thing is that there is virtually no tissue rejection from cheetah to cheetah, so they're all perfect donors for each other. That said, a single zoonosis could wipe them out in the wild.

 

[RichardMNixon]

As a side-note I thought that most people brought up the inbreeding argument just to gross-out the Christian :lol:

My thoughts exactly. I'm worried less about genetics and more about Seth doing his mom in the first couple chapters of the book we should use as a moral compass. :?