Thread: Unexplainable human genetic specialisation

Easy.
Genetic mutation.

In the same way that some people are born with an extra toe through a mutation in their genes, some people are born without an appendix. Seeing as the appendix is not needed, these people survive to pass on the genetic train in their progeny.
Now if there was no cure for a burst apendix, this genetic trait would be passed on much quicker and be more useful because those with no appendix would eventually have an advantage given time.

I'm assuming that there has been a few reported cases of it, and these cases are all linked genetically - not something that is occuring en masse. It can also happen even if the person's parents do not have any history of being born minus appendix. The thing about mutations is that they are random, and without them we wouldn't evolve at all. When evolution stops or slows down dramatically, it doesn't mean that mutations stop at all.

Really there's nothing different, and yes it can be explained by science.

I considered mutation, but discounted it as I was under the impression that it wasn't just one or two families with this condition.
That may have been a horrible assumption. I'll try find out

Keep in mind that mutation is a much slower mechanism, compared to selection

[EDIT]
Alright, after doing a bit more scratching, it seems that the missing appendix is a condition that is very few and far between. That does support that it might be a mutation. Thanks for the reply

However my other concern I raised - for our genetic well - being still applies here: there seems to be no difference in the mortality rate or sexual preference of appendix-endowed people compared to appendix-'challenged' people.
If someone's appendix becomes inflamed, we fix it. If someone gets ill from a condition that an appendix would have avoided, we fix that too.
As such, natural selection will not veer away from such problems.

We 'nerf' the species' natural genetic avoidance systems
At the end of the day ... aren't we damaging our own species' development?

BTW, I found this on the appendix:

...it is clear that these tissues are involved in the body's ability to recognize foreign antigens (molecules to which the immune system can respond) in ingested material[/b]

Well think about this for a second. You only have to live long enough to have a child to pass on you genes. So people who get heart diseases or cancer or anything else that effects you when you are older, wont affect us as a speices.

As for the appendix, if it neither helps nor hurts you then it doesn't matter if theres or not. As long as you dont die without it, there will always be some people without it, because it doesn't hurt them. I am sure people are born without lungs and stuff either, of course they die right away.

This topic is closely skirting the contoversial topic of eugenics. Here's the connection: As we evolve as a species, we depend more and more on the support of a benevolent society. This benevolence, in turn, leads to compassion for those not able to hold their own. Mental Retardation, Muscular Dystrophy, Anemia, Diabetes, Developmental Disabilities -- these are some examples of traits that we are encouraging to participate in out genetic orgy. As such, in order to continue to survive as a species, we must learn how to defeat such fallacies of compassion. We research the human genome and develop genetic treatments. Next, we start tweaking the genetic makeup of our young in vitro. Have you ever seen Atticka? Now we have a separation of classes: Those who were priveliged enough to be awarded superior genes, and those who were born naturaly. Now we get stuck with a superior / inferiror human complex. It is the logical outcome of benevolent social evolution, and it is abominable. So, yes, natural selection is being usurped by mankind. The question is, how do we deal with the inevitable moral dillema to come?

As for the appendix, look at it this way.

1) It takes energy to grow and maintain an appendix.
2) The appendix no longer serves any purpose.
3) Therefore, the energy can be better spent elsewhere in the body rather than producing useless organs.

P.S. It's "Gattaca", not "Atticka".

Originally posted by Placebo

Keep in mind that mutation is a much slower mechanism, compared to selection

Mutation is actually much faster than selection, in fact mutation is the prerequisite for selection.

But yeah, I'd say that we're slowing down our evolution in some of the most obvious survival aspects, but there may be other areas we are still evoloving with, brain capacity maybe. Keep in mind that human civilisation has only really overcome the constraints of evolution in the last.. 60 or so years, as you can see if you look at a graph of world population (the sudden spike where population grows exponentially.)

Gene therapy would overcome this problem - the ability to alter the genes of a living person to cure them. Also, bear in mind that genetic screening is also becoming more common. Now that couples are given the knowledge of whether their unborn child may have a disease, it gives a lot more power to them. As controversial as it may be, maybe there's a point to it. While we might be lessening the impact of natural selection, we are also obtaining more and more power over our own species.

Thanks for the replies guys.

Originally posted by Oneironaut+--><div class='quotetop'>QUOTE(Oneironaut)</div>

This topic is closely skirting the contoversial topic of eugenics [...][/b]

I really appreciate your reply, because that isn't just skirting the issue, it hits the nail on the head of what bothers me. I'll look into eugenics

Originally posted by bradybaker+--><div class='quotetop'>QUOTE(bradybaker)</div>

As for the appendix, look at it this way.

1) It takes energy to grow and maintain an appendix.
2) The appendix no longer serves any purpose.
3) Therefore, the energy can be better spent elsewhere in the body rather than producing useless organs. [/b]

Sure, it makes sense in the traditional genetic selection/specialisation model.
However we aren't part of such an ideal model anymore, as many of the mechanisms of such a model have been compromised, as explained in Oneironaut's post on eugenics.
At the end of the day, I see no reason why genetic specialisation would lean towards not having an appendix - we don't die from it, and we don't seem to benefit a whole lot from it, and it definitely doesn't seem to affect our chance of reproducing our genes.

At this stage, I think mutation might explain it well enough. If we end up having huge groups of people with no appendix, I'll reconsider.

Originally posted by Roller
Mutation is actually much faster than selection, in fact mutation is the prerequisite for selection

Only once the bulk of the genetic 'pool' of options has been fully explored.
Let me explain this way: If you write a genetic algorithm on a computer, you create a population of solutions that are all random. The size of this random population has quite an impact on the speed of development, as there is more variety for the genetic algorithm to choose from. If you had to start with the same size population, but of all the same genes, it would (in my opinion) develop painfully slow.

So unless natural genetic processes have a vastly different mutation rate to a genetic algorithm on a PC... I'd have to believe that selection on an existing variety of options (selection) is a whole lot faster than mutation, followed by selection on that mutation.

With our species, I think we still have quite a bit of variety to play with. Especially now that we are beginning to mix so easily on a global scale.

<!--QuoteBegin-Roller@
But yeah, I'd say that we're slowing down our evolution in some of the most obvious survival aspects, but there may be other areas we are still evoloving with, brain capacity maybe.

Agreed. Brain capacity would make sense to still be able to evolve, however.
Most people want a partner with a level of intelligence greater or at least equal to their own
(With the exception of men who just want a good blond bimbo )

<!--QuoteBegin-Roller
Gene therapy would overcome this problem - the ability to alter the genes of a living person to cure them.While we might be lessening the impact of natural selection, we are also obtaining more and more power over our own species.

This option bothers me, because we still don't know enough about ourselves to start taking our genetics into our own hands, IMO.
I feel we're going to be causing more problems than we fix, when doing this.

The question is whether we are sufficiently capable of directing our own species at this point in time.

Sure, it makes sense in the traditional genetic selection/specialisation model.
However we aren't part of such an ideal model anymore, as many of the mechanisms of such a model have been compromised, as explained in Oneironaut's post on eugenics.[/b]

Although our own cultural evolution happens at a significantly (read as, incredibly) faster pace, this does not mean that we are free of natural selection and other evolutionary processes.

The appendix, like several other vestigial structures in humans, is a waste of energy. Such wastes of energy are slowly de-emphasized and eventually completely 'disregarded' in our genetic make-up.

Also, keep in mind the periods of time that we are talking about with evolution. If 1 out of every 50 people today are born without an appendix, it could be thousands or even millions of years before 45 out of every 50 people are born without one.

So unless natural genetic processes have a vastly different mutation rate to a genetic algorithm on a PC... I'd have to believe that selection on an existing variety of options (selection) is a whole lot faster than mutation, followed by selection on that mutation.[/b]

Surprisingly, scientists studying evolution from a genetic point of view have found that the process of mutation in organisms takes place in a very distinct way. Basically there are long periods of time where not much happen, then all of a sudden there is a significantly large mutation, followed by a brief period of rapid change. (Of course the term \"rapid\" is a bit misleading, we're talking about hundreds, if not thousands of generations).

I refer you back to an article I once posted here, and would be very interested to hear your thoughts on it (or if your thoughts have changed since initially reading it).

http://www.dreamviews.com/forum/viewtopic....=testing+darwin

Most people want a partner with a level of intelligence greater or at least equal to their own[/b]

Actually, research shows that while women look for a more intelligent male partner, males tend to look for a female partner who is less intelligent than themselves. Though obviously this isn't true in all cases. Only the general (fairly significant) trend.

Originally posted by Placebo

So unless natural genetic processes have a vastly different mutation rate to a genetic algorithm on a PC... I'd have to believe that selection on an existing variety of options (selection) is a whole lot faster than mutation, followed by selection on that mutation.

With our species, I think we still have quite a bit of variety to play with. Especially now that we are beginning to mix so easily on a global scale.

Without mutation there would be no variety of options, so in essence they are the same thing; the progress a species makes through mutation is at the same speed as the progress it makes through breeding and variation.

The wonderful thing about DNA is the millions of possibilities there are when passing on genes from one human to the next (or any other eukaryotic organism). The process of sperm and egg production means that there are millions of different possibilities for your genes to be passed on, because of things like independent assortment and crossing over of the chromosones while your sex-cells are being made. When you pair that with the chances of fertilization - of a certain sperm reaching the egg etc - then there are mind-blowing possibilities for variation in the offspring. This basically means that a decent-sized population wil never run out of variation, no matter how much inter-breeding takes place.

Originally posted by Roller+--><div class='quotetop'>QUOTE(Roller)</div>

Without mutation there would be no variety of options, so in essence they are the same thing; the progress a species makes through mutation is at the same speed as the progress it makes through breeding and variation.[/b]

Fair enough. I tend to think in terms of genetic algorithms on a computer, where in that situation you start with a population of random chromosomes. Essentially seeding the variety from the start.
In nature, it may be a bit different. As brady touched on, mutation doesn't stay at the same rate, as it does in a genetic algorithm.

<!--QuoteBegin-brady
Although our own cultural evolution happens at a significantly (read as, incredibly) faster pace, this does not mean that we are free of natural selection and other evolutionary processes.

Not entirely, but it seems to me that we've broken it in particular areas. Thus some parts of our genetics are at a virtual standstill (aside from our fiddling with it), while others will still conform to evolutionary processes.
I feel that the appendix was a section where natural selection had been made moot, as appendixes are not a factor in the choice of a partner, or reproduction.
Mutation, of course, still plays a small role here though

I refer you back to an article I once posted here, and would be very interested to hear your thoughts on it (or if your thoughts have changed since initially reading it).

http://www.dreamviews.com/forum/viewtopic....=testing+darwin[/b]

Thanks, I'll have a look when I get a chance again (probably tomorrow)
The time I have for such things has dropped quite badly, for a variety of reasons including my ADSL provider disconnecting me erroneously.

Originally posted by Placebo
Not entirely, but it seems to me that we've broken it in particular areas. Thus some parts of our genetics are at a virtual standstill (aside from our fiddling with it), while others will still conform to evolutionary processes.
I feel that the appendix was a section where natural selection had been made moot, as appendixes are not a factor in the choice of a partner, or reproduction.
Mutation, of course, still plays a small role here though

You have to consider the dynamics of large populations when thinking about our evolution as a species.

Sure, to you or me, whether or not some girl has an appendix isn't going to determine whether we're attracted to her. But on massive scales (6 billion people) an appendix or lack thereof becomes significant.

If the energy that it takes to produce an appendix can be better used to increase brain capacity or physical stamina or whatever else, this will lead to a miniscule advantage for the non-appendix people in the real world.

This minscule advantage inflates into a full-fledged trend when applied to all of humanity. It still takes millions of years to see results, but the process is there and working as well as ever.

eh I'd written a nice long reply.... and then my computer shut down grr. I wish i'd kept my biology books from school instead of selling them, this is all off the to of my head... it's good fun remembering it all though.

Sigh. Ok let's start that again.

Basically what I was saying is that the processes of independent assortment, crossing over and even fertilization all have an effect on variation, and maybe that's something these algorithm programs dont' properly take into account... I don't know because I don't have much knowledge of the programs, but there definatley is a lot more contributing to variation than simply random initial population or mutation.

I'll explain Meiosis, and how crossing over etc increase variation. If you already are familiar with it all then bare with me... I'm doing this off the top of my head from what I learnt in school last year. Eh on second thoughts i'm goig to type this in word so i can save it in case my comp fucks again.

Ok… Meiosis is the process of producing gametes (sex cells ie, eggs, sperm) from normal cells. A normal human cell contains 46 chromosomes, 23 maternal (passed on from your mother) and 23 paternal (passed on from your father). Right, when a cell is about to undergo Meiosis 1 stage of Meiosis the maternal and paternal chromosomes all pair up in homogulous pairs. This means that say… chromosome 10 from the paternal side pairs up with the corresponding chromosome 10 from the maternal line.

When they are in their homogulous pairs, they do what is called ‘crossing over’ (no, they don’t talk to dead people). In crossing over, a random piece from the paternal chromosome is snipped off and exchanged with the corresponding piece from the maternal chromosome. Despite both of the pieces being corresponding, they contain different genetic information, thus ensuring that each chromosome is mixed around. This exchange of information happens at random, and to each of the 23 homogulous pairs. As you can probably see from this, already the chances of any two offspring being genetically the same has been reduced enormously, thus creating more variation.

After crossing over, the homogulous pairs line up along the middle of the cell, creating two lines of 23 chromosomes, side by side. Now as they line up along side each other they go through another process called ‘independent assortment’. Basically this means that as the chromosomes form the two lines, they do so independent of each other, meaning that all the 23 paternal chromosomes will not try and form in the same line. The result is that both lines contain a mix of both maternal and paternal chromosomes so that when the cell splits in two both of the new cells will have a further mix of genetic material.

So there are two cells, both haploid (23 chromosomes). They contain a mix of genetic material, and when they undergo Meiosis 2 stage - which is a further splitting of the cells – they will each have vastly different genetic makeups. Now every chromosome in a normal cell is made up of two ‘Sister Chromatids’ connected at the middle (the Centromere), thus forming the distinctive X shape. Normally, as their name suggests, Sister Chromatids are simply two copies of the same genetic information. In Meiosis and the formation of sex cells they are changed due to the process of crossing over, so that one of the Chromatids will contain different information to the other. When the cells undergo the splitting of Meiosis 2, the result is four gametes, each with significantly different genetic information.

We now have four gametes with randomly selected genetic information from the maternal and paternal chromosomes, with the information of one cell divided and mixed into four. The chances of any two offspring ever being identical are now even lower. Keep in mind that during this whole process, mutation could have formed very easily, thus contributing entirely new information.

We now come to the final and certainly the most pleasurable stage of sexual reproduction – fertilization. Now we have a huge number of factors coming into play; not only do we have the complete randomisation of the sperm cells, but the whole process of Meiosis has also happened to produce the eggs of the female. If we took just one egg and one sperm to form a zygote (fertilized cell) then the chances of being able to produce another genetically identical zygote are mind-blowing. Then you consider that simply the time of fertilization plays a part, determining whether one egg is fertilized one month or a different egg another month. On top of this we have the millions of sperm, and the chances of one sperm fertilizing the egg over another.

So… take a step back and a deep breath. What are the chances of a man and a woman producing two genetically identical offspring from separate fertilizations? Well I’d go so far as to say it is impossible. A woman produces something like 56 eggs from puberty to menopause, and not ever single one of these is able to be fertilized… a man will produce millions of sperm in his lifetime, yet only a small fraction will ever do what it was intended for.

From this we see that even between two people the amount of genetic variation possible is enormous, mind-blowingly enormous, as genetic information is randomised, mixed and matched. Also, I think each person should feel very lucky to be alive haha.

Well that’s my very long-winded explanation… sorry if it’s hard reading it all, but the whole process of Meiosis is so complicated that it takes a lot to bend your mind around it (zygote, haploid, diploid, meiosis 1, meiosis 2, independent assortment, crossing over, chromatids… ehh it’s a wonder I ever memorized it all for my exams.) I love biology for the reasons that everything that looks simple is actually so damn complex, and whey you understand the complexity it gives you a completely different look on life.

But yeah… there definitely is a lot more to variation than population and mutation . This isn’t even talking about the fact that in the offspring some of the genes will be dominant or recessive, ending up with a entirely different individual than the genes might suggest.

That’s all for now lol.

Thanks for the info, I did know the biology (I've researched it quite a lot in wikipedia ), but it was probably informative for a lot of people on this forum, so thanks

About the source of variation:

You ask what the chances are of having the same child twice. Sure, that's virtually impossible. But let me ask this: What are the chances of the two children having the same colour eyes? Generally about 1 in 4 at worst.
I think you slightly misunderstand what I mean about the source of variation... I'll try to explain.

Look at it like the lottery. The chances of getting the same lottery number twice are basically impossible. But the chances of getting a particular number in both draws isn't too bad.

Crossing over of the genes results in a wide variety of different aspects of a human being, that together make a unique individual, as you point out.
However each one of those genes only has about 4 possibilities at most - because of the diploid nature of our cells, we hold 2 genes for each possible trait, and because of dominance (ie whichever gene is more efficient tends to 'win') only one gets used (usually, sometimes they both get used) But when we reproduce, either of those two genes can be passed on. Not both.
That means there is genetic material in your great grandparents that no longer exists in the gene pool at all - simply because they could only pass on one gene for each trait, not two.

Thus the natural selection and crossing over of genes results in a MIX of gene traits (alleles), but not completely new ones. Only mutation, or introduction of new genetic material, can do that - which is what I mean about the source of variation being only mutation and initial population (or new population introduced?)

Another way of explaining : The only way the possible lottery balls in a draw can change is by adding new balls, or changing existing ones. Not by mixing them around before a draw

ie. Natural selection allows the variation to be mixed together, but does not allow for new variation in each gene trait.

I dunno if I'm explaining that well enough

Ahh I'm with you now... Hmm perhaps we should go and have sex with as many different women as possible... all in the name of 'furthering the gene pool'.

Originally posted by Roller
Ahh I'm with *you now... Hmm perhaps we should go and have sex with as many different women as possible... all in the name of 'furthering the gene pool'. *

Yep, hows next weekend? We can meet up at a local bar
It does bring a new perspective to why biblical characters had so many kids and concubines, and put so much emphasis on genealogy.