Genetic testing...achondroplasia

[Jochi1543]

Someone said it's kind of like being francophone - and they too feel strongly about their culture.

 

I'm sorry, but that's gotta be the dumbest analogy I've ever heard. Being deaf is like being francophone? Francophones can learn to speak English, but deaf people can't learn to hear (or speak, since many also can't speak), and they can't choose when to be deaf and when to hear.

[drcave]

I think for homosexuality to be considered biologically abnormal it would have to be absent from other species and have no selective advantage. Bonobo chimps engage in homosexual acts on a regular basis so there goes the first point. Also, homosexuality confers a selective advantage through kin selection. Imagine caveman Thag and his gay brother Thog. Thog has no kids of his own, but stays with Thag and helps him to bring home more giant sloth meat and raise more cavechildren then Thag could have done on his own. Because they are brothers and share half their DNA, Thog increase the chances of passing on the homosexuality gene. Given the selective advantage through kin selection, I wouldn't be surprised if there were other examples of homosexuality in animals. How many times have you seen two male mallard ducks hanging out together?

[The Law]

I think for homosexuality to be considered biologically abnormal it would have to be absent from other species and have no selective advantage. Bonobo chimps engage in homosexual acts on a regular basis so there goes the first point. Also, homosexuality confers a selective advantage through kin selection. Imagine caveman Thag and his gay brother Thog. Thog has no kids of his own, but stays with Thag and helps him to bring home more giant sloth meat and raise more cavechildren then Thag could have done on his own. Because they are brothers and share half their DNA, Thog increase the chances of passing on the homosexuality gene. Given the selective advantage through kin selection, I wouldn't be surprised if there were other examples of homosexuality in animals. How many times have you seen two male mallard ducks hanging out together?

 

Good point, I never thought of it from that standpoint.

[clkt]

ok, how about this.

If the parents can purposefully select for a disabling trait with the help of the taxpayers' money, should taxpayers pay for their child's treatment as well? Treatment being whatever extra medical attention or physiotherapy that such disabled child requires.

[Devari]

How is it abnormal biologically?

 

Do I really have to explain this? No offense, but if I have to provide an explanation as to why homosexuality is not a normal biological condition I think it may be impossible to have a meaningful discussion with you on this topic.

 

You may think it may be, due to natural selection - however genes associated with homosexuality may perhaps be associated with other genes that cause them to continually be transferred (correlated progression). Additionally, carrying such genes may not automatically result in homosexuality either, so would not reduce a person's "biological fitness" necessarily. I have a feeling this is going to spin off the topic... lol

 

Until scientific studies provide clear evidence as to whether homosexuality is primarily determined by genetics, developmental issues or psychological issues we simply won't know what the underlying causes are. This is why scientific studies are necessary if homosexuality is ever going to be understood from a biological perspective. Unfortunately, I suspect that political considerations will prevent any actual progress in terms of an actual scientific understanding, since there's almost no way to study the issue objectively without offending someone.

 

I think for homosexuality to be considered biologically abnormal it would have to be absent from other species

 

Wrong. Cancer is present in many species but this doesn't make cancer a normal condition in either a biological or medical sense.

 

and have no selective advantage.

 

Since the selective disadvantage of homosexuality is essentially equivalent to being sterile since no offspring are produced and there is no conceivable selective advantage to this behavior there is no conceivable reason homosexuality would be selected for in nature. It can of course exist as an abnormality inherent to a species simply because biological systems are inherently imperfect, but the simple fact that it exists doesn't mean that it necessarily has any "purpose".

 

Bonobo chimps engage in homosexual acts on a regular basis so there goes the first point.

 

See above. Your first point is wrong.

 

Also, homosexuality confers a selective advantage through kin selection.

 

Wrong.

 

Imagine caveman Thag and his gay brother Thog. Thog has no kids of his own, but stays with Thag and helps him to bring home more giant sloth meat and raise more cavechildren then Thag could have done on his own. Because they are brothers and share half their DNA, Thog increase the chances of passing on the homosexuality gene. Given the selective advantage through kin selection, I wouldn't be surprised if there were other examples of homosexuality in animals. How many times have you seen two male mallard ducks hanging out together?

 

This simply doesn't make any sense. Why does Thog need to be homosexual to work with Thag? If Thog was heterosexual he could not only work together with Thag, he could also raise his own family and pass on his own genetic material. There's simply nothing that Thog gains by being homosexual, but he loses the chance to have offspring of his own. You're trying to ascribe a completely separate and unrelated social behavior (social cooperation) with a biological abnormality (homosexuality). There is simply no logical reason to link these two behaviors. One has absolutely nothing to do with the other.

 

I realize that I'm being very blunt in my responses but I tend to get really annoyed when people refuse to look at things logically. When I make a simple factual statement that "from a biological perspective homosexuality is clearly abnormal" and people try to argue with this I get the sense that the discussion is rapidly going downhill. I've intentionally stayed away from the religious or social issues with homosexuality because those are extremely difficult to discuss objectively, but everyone should be able to understand that homosexuality is not normal behavior in a biological context. This doesn't require any formal training in biology or involve any difficult concepts, it's just common sense.

[The Law]

Do I really have to explain this? No offense, but if I have to provide an explanation as to why homosexuality is not a normal biological condition I think it may be impossible to have a meaningful discussion with you on this topic.

 

Despite the fact that it is seen across many species of animals?

 

Until scientific studies provide clear evidence as to whether homosexuality is primarily determined by genetics, developmental issues or psychological issues we simply won't know what the underlying causes are.

 

Exactly, which is why you can't claim it is irrelevant biologically. If it has any genetic basis it is relevant biologically, and the fact that it is seen in different animals may indicate that fact.

 

You seem to have a really arrogant attitude, simply because people don't agree with you on what may appear "logic" to you, does not give you the right to speak to us in your self-righteous tone. Also, you said that it may be a "flaw" in the biology... great scientific reasoning. You can't just dismiss an argument, just because it doesn't fit your opinion. Open-mindedness is one of the cornerstone's in science.

 

Since the selective disadvantage of homosexuality is essentially equivalent to being sterile since no offspring are produced and there is no conceivable selective advantage to this behavior there is no conceivable reason homosexuality would be selected for in nature.

 

This doesn't take into account the possibility of correlated progression, combined with the fact that it may not be completely biological (and thus allowing the genes to continually pass down if they are being transferred with highly adaptive traits).

[Madz25]

I realize that I'm being very blunt in my responses but I tend to get really annoyed when people refuse to look at things logically. When I make a simple factual statement that "from a biological perspective homosexuality is clearly abnormal" and people try to argue with this I get the sense that the discussion is rapidly going downhill. I've intentionally stayed away from the religious or social issues with homosexuality because those are extremely difficult to discuss objectively, but everyone should be able to understand that homosexuality is not normal behavior in a biological context. This doesn't require any formal training in biology or involve any difficult concepts, it's just common sense.

 

LOL. Maybe your discussions go down hill because they aren't discussions at all. It just seems like you are unable to open your mind to other opinions yet want other people to accept your opinions as being true. Just because YOU think that your statements are logical, doesn't make them right. If you know anything about science, often something that seems logical isn't always the case. Maybe you should try to be more open-minded and your discussions may actually end up BEING discussions.

[Devari]

Despite the fact that it is seen across many species of animals?

 

How is that relevant? Cancer is seen in many animals but that doesn't make cancer a biologically normal condition.

 

Exactly, which is why you can't claim it is irrelevant biologically. If it has any genetic basis it is relevant biologically, and the fact that it is seen in different animals may indicate that fact.

 

You seem to have a really arrogant attitude, simply because people don't agree with you on what may appear "logic" to you, does not give you the right to speak to us in your self-righteous tone. Also, you said that it may be a "flaw" in the biology... great scientific reasoning. You can't just dismiss an argument, just because it doesn't fit your opinion. Open-mindedness is one of the cornerstone's in science.

 

See my posts above. I've specifcally addressed problems with some of the comments that were posted. If you want to call that arrogance, go ahead. All I'm doing is addressing this topic in an objective manner and pointing out logical flaws in certain ideas that have been presented. If you can't handle an objective discussion without getting offended, that's not my problem.

 

This doesn't take into account the possibility of correlated progression, combined with the fact that it may not be completely biological (and thus allowing the genes to continually pass down if they are being transferred with highly adaptive traits).

 

You need some basis for this type of argument. Saying "maybe homosexuality is being propagated for a reason" needs to have something to back it up. You seem to have made an arbitrary assumption that there needs to be some "reason" for homosexuality to exist. This isn't necessarily the case at all. Homosexuality could simply be an abnormality that arises due to the fact that biological development is never 100% perfect and abnormalities will arise spontaneously due to the complexity of the biological systems in question.

 

LOL. Maybe your discussions go down hill because they aren't discussions at all. It just seems like you are unable to open your mind to other opinions yet want other people to accept your opinions as being true. Just because YOU think that your statements are logical, doesn't make them right. If you know anything about science, often something that seems logical isn't always the case. Maybe you should try to be more open-minded and your discussions may actually end up BEING discussions.

 

If you knew anything about science you'd understand that even though a biological system may not operate in a logical manner the study of science itself must be based on logic. If somone makes a flawed or incomplete argument in a scientific discussion they can't complain when their idea is subject to criticism. I'm not going to tell someone that their idea is wonderful if it has flaws. I'm going to point out those flaws in a concise and direct manner. As a scientist I do this every day and my own ideas are in turn subject to the same type of critical review. I couldn't care less if someone can't handle this type of discussion and gets offended. If certain people can't handle a rational discussion that's their problem, not mine.

[Artemis]

I'm sorry, but that's gotta be the dumbest analogy I've ever heard. Being deaf is like being francophone? Francophones can learn to speak English, but deaf people can't learn to hear (or speak, since many also can't speak), and they can't choose when to be deaf and when to hear.

 

Well actually, it was a deaf person who told me that analogy. Sorry, I will run and tell them they are wrong.

[Artemis]

I think for homosexuality to be considered biologically abnormal it would have to be absent from other species and have no selective advantage. Bonobo chimps engage in homosexual acts on a regular basis so there goes the first point. Also, homosexuality confers a selective advantage through kin selection. Imagine caveman Thag and his gay brother Thog. Thog has no kids of his own, but stays with Thag and helps him to bring home more giant sloth meat and raise more cavechildren then Thag could have done on his own. Because they are brothers and share half their DNA, Thog increase the chances of passing on the homosexuality gene. Given the selective advantage through kin selection, I wouldn't be surprised if there were other examples of homosexuality in animals. How many times have you seen two male mallard ducks hanging out together?

 

There have definitely been some interesting points brought up here. With this particular idea, there is one big problem I cannot get past. Even if kin selection or correlated progresion were factors, it still rests that a homosexual organism will not have offspring. In order for a gene to be passed down, reproduction is necessary. Really, the gene in question would have the same effect on reproductive fitness as that of a lethal gene. In the case of lethal genes, they still persist in the population primarily because of heterozygous advantage, however it is extremely rare that they present themselves in the homozygous state. This however is not seen with homosexuality, as it is nowhere near as rare in nature, as has already been discussed.

[Jochi1543]

Well actually, it was a deaf person who told me that analogy. Sorry, I will run and tell them they are wrong.

 

Just because 1 deaf person thinks that way doesn't mean it applies to every single deaf person out there.

[Madz25]

If you knew anything about science you'd understand that even though a biological system may not operate in a logical manner the study of science itself must be based on logic. If somone makes a flawed or incomplete argument in a scientific discussion they can't complain when their idea is subject to criticism. I'm not going to tell someone that their idea is wonderful if it has flaws. I'm going to point out those flaws in a concise and direct manner. As a scientist I do this every day and my own ideas are in turn subject to the same type of critical review. I couldn't care less if someone can't handle this type of discussion and gets offended. If certain people can't handle a rational discussion that's their problem, not mine.

 

WOW. Why are you so quick to attack? I actually agree with some of your points but the way you present them and the way you respond to others is ....well simply awful. I hope you're not like this in your med interviews...

 

 

Maybe the mods can lock this thread? It's clearly going no where and is going to end badly...if it already hasnt reached that point. Thanks.

[The Law]

If you knew anything about science you'd understand that even though a biological system may not operate in a logical manner the study of science itself must be based on logic. If somone makes a flawed or incomplete argument in a scientific discussion they can't complain when their idea is subject to criticism. I'm not going to tell someone that their idea is wonderful if it has flaws. I'm going to point out those flaws in a concise and direct manner. As a scientist I do this every day and my own ideas are in turn subject to the same type of critical review. I couldn't care less if someone can't handle this type of discussion and gets offended. If certain people can't handle a rational discussion that's their problem, not mine.

 

Well thank you for enlightening me Mr Nobel.

 

[JewelLeigh]

Well thank you for enlightening me Mr Nobel.

 

 

LOL! I love it.

[The Law]

LOL! I love it.

 

LOL, someone had to say it. hahaaha

[drcave]

 

Since the selective disadvantage of homosexuality is essentially equivalent to being sterile since no offspring are produced and there is no conceivable selective advantage to this behavior there is no conceivable reason homosexuality would be selected for in nature. It can of course exist as an abnormality inherent to a species simply because biological systems are inherently imperfect, but the simple fact that it exists doesn't mean that it necessarily has any "purpose".

 

 

This simply doesn't make any sense. Why does Thog need to be homosexual to work with Thag? If Thog was heterosexual he could not only work together with Thag, he could also raise his own family and pass on his own genetic material. There's simply nothing that Thog gains by being homosexual, but he loses the chance to have offspring of his own. You're trying to ascribe a completely separate and unrelated social behavior (social cooperation) with a biological abnormality (homosexuality). There is simply no logical reason to link these two behaviors. One has absolutely nothing to do with the other.

 

 

You don't seem to understand kin selection. Because gay Thog won't have children, his energy can be spent helping to raise his brothers children which will have many of his genes including any genes that predispose or predetermine homosexuality. Why would he help his brother? Because of the tight family bond and his own selfish genes. From the viewpoint of his genes by raising nieces and nephews Thog is a reproductive success.

 

From wikipedia:

 

In evolutionary biology, kin selection refers to changes in gene frequency across generations that are driven at least in part by interactions between related individuals, and this forms much of the conceptual basis of the theory of social evolution. Indeed some cases of evolution by natural selection can only be understood by considering how biological relatives influence the fitness of each other. Under natural selection, a gene encoding a trait that enhances the fitness of each individual carrying it should increase in frequency within the population; and conversely, a gene that lowers the individual fitness of its carriers should be eliminated. However, a gene that prompts behaviour which enhances the fitness of relatives but lowers that of the individual displaying the behavior (i.e. kin selection), may nonetheless increase in frequency, because relatives often carry the same genes. The enhanced fitness of relatives can at times more than compensate for the fitness loss incurred by the individuals displaying the behaviour.

Contents

Hamilton's rule

 

Formally, such genes should increase in frequency when

 

rB − C > 0

 

where

 

r = the genetical relatedness of the recipient to the actor, usually defined as the probability that a gene picked randomly from each at the same locus is identical by descent.

B = the additional reproductive benefit gained by the recipient of the altruistic act,

C = the reproductive cost to the individual of performing the act.

 

This inequality is known as Hamilton's rule after W. D. Hamilton who published, in 1964, the first formal quantitative treatment of kin selection to deal with the evolution of apparently altruistic acts. The phrase Kin selection, however, was coined by John Maynard Smith.

 

Technically, the correct definition for relatedness ® in Hamilton's rule describes it as a regression measure. Regressions, unlike probabilities, can be negative, and so it is possible for individuals to be negatively related, which simply means that two individuals can be less genetically alike than two random ones on average. This has been invoked to explain the evolution of spiteful behaviours.

 

In the 1930s J.B.S. Haldane had full grasp of the basic quantities and considerations that play a role in kin selection. He famously said that, "I'd lay down my life for two brothers or eight cousins".[1] Kin altruism is the term for altruistic behaviour whose evolution is supposed to have been driven by kin selection.

 

Haldane's remark alluded to the fact that if an individual loses its life to save two siblings, four nephews, or eight cousins, it is a "fair deal" in evolutionary terms, as siblings are on average 50% identical by descent, nephews 25%, and cousins 12.5% (in a diploid population that is randomly mating and previously outbred). But Haldane also joked that he would truly die only to save more than one identical set of twins or more than two full siblings.

 

[edit] Mechanisms

 

Hamilton (1964) outlined two ways in which kin selected altruism could be favoured.

 

Firstly, if individuals have the capacity to recognise kin (kin recognition) and to adjust their behaviour on the basis of kinship (kin discrimination), then the average relatedness of the recipients of altruism could be high enough for this to be favoured. Because of the facultative nature of this mechanism, it is generally regarded that kin recognition and discrimination are unimportant except among 'higher' forms of life (although there is some evidence for this mechanism among protozoa). A special case of the kin recognition/discrimination mechanism is the hypothetical 'green beard', where a gene for social behaviour also causes a distinctive phenotype that can be recognised by other carriers of the gene. Hamilton's discussion of greenbeard altruism serves as an illustration that relatedness is a matter of genetical similarity and that this similarity is not necessarily caused by genealogical closeness (kinship).

 

Secondly, even indiscriminite altruism may be favoured in so-called viscous populations, i.e. those characterised by low rates or short ranges of dispersal. Here, social partners are typically genealogically-close kin, and so altruism may be able to flourish even in the absence of kin recognition and kin discrimination faculties. This suggests a rather general explanation for altruism.

 

Social insects are an excellent example of organisms that display kin selected traits. The workers of some species are sterile, a trait that would not occur if individual selection was the only process at work. The relatedness coefficent r is very high between the worker hymenoptera due to haplodiploidy, and Hamilton's rule is satisfied because the benefits in fitness for the queen are reflected in indirect fitness for the individual workers, and the increased efficiency provided by group living means that the costs are far outweighed by the benefits.

[Smurfette]

Thanks drcave. I only have a few things to add to your nice little explanation of evolutionary biology.

 

From an evolutionary biology point of view, it is not individuals that matter but genes. Hence, individuals may be self-sacrificing, may be altruistic, etc. but genes are not. It makes sense to protect your own genes - many of which you might share with your siblings. Homosexuality in animal groups mostly exist in social groups, where social interactions are important. As drcave pointed out this includes the well-known examples of social insects, but it also includes mammals that form small social groups such as lions. It has been shown that men with more older brothers are more likely to be homosexual. This seems to make a lot of sense evolutionarily because the more males there are, the less likely they are to find a mate and so it makes more sense to increase the reproductive fitness of their brothers' children whose genes they share. It may work in a similar fashion in females, as female concubines in ancient China (literally hundreds of females for a few males) also displayed homosexual activity. Why homosexuality in order to produce this effect? In the first example, they could simply help out their older brothers with their kids and still be heterosexual. This is true, but my guess (not backed up with any reading or scientific research) is that a male would feel the competition with a heterosexual male hanging around my family (my kids and my wife). Homosexuality may in fact be a social signal that they are not competing sexually with the first male.

 

Homosexuality was considered to be abnormal in Western culture approximately 50 years ago. That view is slowly starting to change. It is not considered to be abnormal in some other cultures. In some ancient Aboriginal cultures, homosexuals were integral parts of the social stucture and were celebrated and desired as people who would help take care of children.

 

I am not saying that I necessarily think that homosexuality can be very simply explained by evolutionary biology. While evolution is an interesting paradigm to use to view the world, it is simply a paradigm or a model of the world - as are most things in science. However, I do think that it is a misuse of the principles of evolution, to assume that particular behaviours are abnormally, especially when these behaviours are actually quite prevalant in society (estimated 10-40% of people have engaged in homosexual acts and 5% of people are exclusively homosexual).

 

This is an entirely different issue, but I believe that the problem with evolutionary biology and sociobiology, historically and probably in today's society as well, is that many people tend to use these ideas in order to support their political beliefs. Unfortunately, it has been incorrectly used to rationalize selfishness, to label various groups "abnormal" or "wrong", and to call various races "inferior".

 

P.S. If you're wondering, I am a heterosexual female.

[drcave]

 

P.S. If you're wondering, I am a heterosexual female.

 

No doubt! A little blue heterosexual female, in fact the only little blue heterosexual female in a village full of hundreds of little blue men (who probably don't need little blue pills, except maybe Papa Smurf but he's old). Hmmmm. Your idea of Utopia?

[AMmd]

man, biology is not all about genetics... you also have to take into consideration environmental factors...

the reason why (biological) children of homosexuals are not gay is probably due to the fact that homosexuality is not caused by a single "gay" gene... it is very multifaceted, and you cannot simply say what doesnt fit this mold is absorlutly wrong.

Man devari, you need to chill dude... if you like logic so much maybe you should go into math or physics...

[The Law]

No doubt! A little blue heterosexual female, in fact the only little blue heterosexual female in a village full of hundreds of little blue men (who probably don't need little blue pills, except maybe Papa Smurf but he's old). Hmmmm. Your idea of Utopia?

 

LOL!! drcave you're too funny.

[Devari]

You don't seem to understand kin selection. Because gay Thog won't have children, his energy can be spent helping to raise his brothers children which will have many of his genes including any genes that predispose or predetermine homosexuality. Why would he help his brother? Because of the tight family bond and his own selfish genes. From the viewpoint of his genes by raising nieces and nephews Thog is a reproductive success.

 

The problem with this entire idea is that you assume that Thog has some implicit understanding or motivation that is based on this concept and will act accordingly. This doesn't have any rational basis because Thog doesn't understand molecular genetics and has neither a conscious nor an instinctive understanding of this idea. The only behavior you can logically ascribe to Thog is that he will likely spend his time and resources trying to have sexual relations with other cavemen. That's what Thog's homosexual sex drive will be telling him to do. Why would Thog waste time helping Thag raise his children when he could be chasing after other cavemen instead? The fact that Thag happens to share some of Thog's genes is completely irrelveant. Being homosexual has absolutely nothing to do with increased social cooperation with siblings, it has to do with a person's sex drive.

 

See what I'm getting at here? You can't just arbitrarily link homosexuality to a completely unrelated behavior. Assuming that Thog is going to be more likely to devote his energy and resources to helping Thag simply doesn't make any sense here. You're trying to suggest that Thog is going to ignore his homosexual sex drive and channel his resources into helping a sibling instead. Sorry, but that's just not a rational idea.

[The Law]

I think it's time to agree to disagree.

[vogue]

See what I'm getting at here? You can't just arbitrarily link homosexuality to a completely unrelated behavior. Assuming that Thog is going to be more likely to devote his energy and resources to helping Thag simply doesn't make any sense here. You're trying to suggest that Thog is going to ignore his homosexual sex drive and channel his resources into helping a sibling instead. Sorry, but that's just not a rational idea.

 

Devari, you are right on the money:)

[The Law]

Alright, discussion of this topic is now ending.

This debate is highly polarized and will just lead to problems... a mod needs to lock this thread.

[drcave]

I haven't noticed any problems. It's not getting nasty, nobody is calling anybody names.

 

Whats the best place to chase cavemen - why out on an all-male hunting party of course.

 

I suppose Devari would argue that altruistic prairie dogs that stand and chirp to warn their kin about predators, risking their own survival, only do so because they understand the concept of kin selection.

 

 

Another theory of about why male homosexuality is heritable is that it is a multi gene trait with a number of genes that each result in more feminine traits such as senitivity, compassion etc., traits that have selective advantages for the individual. But if too many of these traits appear in one inidvidual the result is a tendancy towards homosexuality.

 

An accumulation of evidence points to homosexuality being heritable (not to say that nurture has no effect). The question is why?