Talk:Heterosis

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String theory[edit]

For the person who wanted to delete the heterotic string: I am sorry, but if you look at the history of this page, you will see that this page was established because of string theory - and it is genetic which is secondary. The picture of the dog is nice, but eliminating references to string theory is vandalism because the heterotic string is quite certainly more important than some dogs of an uncertain pedigree. --Lumidek 16:38, 28 Sep 2004 (UTC)

I didn't "vandalize" the page by commenting out the reference to string theory. I came to a page that had a bizarre, unmotivated reference to string theory; not knowing the details of string theory, I represent a typical, lay Wikipedia user. Rather than removing the link entirely, I commented out the link and requested justification to a reference to string theory. You have provided that justification. If I had never commented out the link, you wouldn't have explained why string theory should be referenced and we'd be left with a shoddy, bizarre connection between genetics and string theory. Together, we have have improved Wikipedia. --WpZurp 22:27, 28 Sep 2004 (UTC)

Reverse hybrid vigor[edit]

Can someone cite sources for the section on "reverse hybrid vigor"? The only Google results I find for this term are for Wikipedia and its mirrors. Aero34 05:04, 3 Jan 2005 (UTC)

Regarding the addition of 'some stinky dogs'[edit]

I don't know how many of the uninitiated would understand the reference to heterotic string; I'm guessing it wouldn't be many. However, the words "hybrid vigour" incite passionate debate in the various animal fancy groups. "Heterosis" just happens to be the proper term for this phenomenon. I'm sure no disrespect was meant to string theory, but believe me it's more than just a question of a few stinking dogs, or cats, or horses, or cows, or....Thanks for the chuckle! Quill 04:30, 3 Apr 2005 (UTC)

Importance/expansion[edit]

Personally I think the concept of heterosis is extremely important from a biological and evolutionary point of view- I'd love to see someone expand this with some hard science, casting a bigger net than is cast now. Kharhaz

Racist?[edit]

This article is kind of racist, and is based on vauge and arbitrary definitions of "better" that have been tied to evolution through lay-person gossip for years. I have a mind to take out everything that I can't find a credible source for.

Hey, thanks for your improvements to the article. If your comment is referring to the heterosis studies in humans, the science and its presentation here are limited to dealing with higher and lower scores for said measurement. The section's references appear to be in order. I have though, added a note to "see race and intelligence" for appropriate caveats.--Nectar T 23:19, 10 November 2005 (UTC)
By definition, race mixing is good.... --108.173.175.220 (talk) 07:40, 4 July 2012 (UTC)

Spock[edit]

I am taking out the spock bit and I do not believe it to be vandalism to do so. I know I'm going to be the biggest trekkie for knowing this, but the character doesn't see himself as a superior hybrid, nor does the show see it that way- he's superior in many ways to humans because he was raised among the technologically advanced and all over controlled Vulcans. But I'm not the crazy trekkie in this situation, I'm making the deduction anyone would make, the off, overthought and under represented in the show opinion is that spock is supposed to be better from being not-inbred. It's about an interracial family, a man constantly proving himself to be logical despite his humanity- it's not a story about evolution in a truly scientific sense.

Also, I think it's worth mentioning and scientific to say that for heterosis in humans, humans don't have a diverse enough genepool for hybrid vigor to matter. This explanation could help people understand the concept of heterosis in general. 66.41.66.213 15:08, 11 November 2005 (UTC)lotusduck

I reinserted fictional Mr Spock because regardless of how the character sees himself, he does inherit Vulcan mental powers from his father that have frequently saved the starship and its otherwise human crew. IMO there is no good reason to comment on possible speculative interpretations of Spock in terms of human races or evolution.Cuddlyable3 14:55, 10 September 2007 (UTC)
To claim that "humans don't have a diverse enough genepool for hybrid vigor to matter" would need sources for verification that I don't think can be found, plus a clarification of what "matters".Cuddlyable3 14:55, 10 September 2007 (UTC)

Removed Spock reference. It's just silly and the ST canon does not support this statement.

Which statement do you claim is unsupported? Please sign your posts.Cuddlyable3 15:52, 13 September 2007 (UTC)

You are trying to take a scientific page and make it a joke by entering spock comments... use facts not fictional characters.... — Preceding unsigned comment added by 149.164.242.129 (talk) 15:22, 25 October 2011 (UTC)

Heterosis in humans[edit]

removed:

  • Heterosis in humans must be interpreted differently than heterosis in other organisms, because the entire human population already has a very limited gene pool. Heterosis functions as the opposite of inbreeding, and in this way we know limited heterosis in humans to exist; humans who have offspring with close relatives have unfit offspring, so the children of unrelated pairs by comparison are an example of hybrid vigor. However, because of the limited gene pool in humans, the mating of one human from one race and another human of a historically isolated race is analagous to one chimpanzee mating with a cousin.

These statements would need citation.--Nectar T 01:38, 14 November 2005 (UTC)

has only intelligence ever been tested wrt heterosis in humans? That would seem rather stupid, seeing the fabulous obstacles connected with any measurement of intelligence. Has nobody measured much more straightforward traits, such as physical strength, immune reaction, reflexes, etc. ? Also, just studies on plants... and humans? Nothing on animals? 83.76.222.64 14:14, 22 July 2006 (UTC)

Do we really need half this article to be about skin whiteners? 68.189.104.46 01:57, 28 June 2007 (UTC)

Genetic basis of heterosis[edit]

I think it is important to mention the genetic basis of heterosis. It is what is at the base of this phenomenom. I tried to explain it at best I could and provide a figure (which I admit, could be of better quality. Suggestions?). Any comments, remarks about it? It will also need references. Seb951 16:18, 24 February 2006 (UTC)seb951

Better![edit]

I'd like to issue a public thank you to the Wikipedia community for their attention to this area. This article has defiantly shown an improvement and is closer to scientifically accurate after my posts. It is a big responsibility that Wikipedia has, and that responsibility should be free of cultural bias, even if it may seem to go against what we have been led to believe by American media and culture.

When I first started looking into this topic, the articles I found were woefully inaccurate and defiantly biased. I still feel that objectively, the definition should clearly state that most cross-breeds lead to a reduction in fitness. Heterosis can be induced through breeding stragity such as line-breeding but it is a wasteful effort. Random mixing of genes is similar to random mutation, most of which is deadly and not beneficial to the gene pool. 99% of mutations are deleterious.

Respect of natural selection should be the default position. There are quantifiable difference between the races which were developed over hundreds of generations and whatever diversity we have managed to achieve should be cherished, what makes us different is what makes us special. By mixing the races, in one or two generations we can undo the work of hundreds or thousands of years of evolution.

only deviant humans race mix anyway so dont worry i tink. most people stick whit thier own kind.

What the hell is this ridiculous garbage?204.97.106.20 21:37, 25 June 2007 (UTC)
Heterosis is not the same as random mutation. Random mutation is referred to as genetic drift and it is not as harmful as you claim. Humans mating out of their race will not eliminate much. Blonde hair for example, would not disappear.YVNP (talk) 08:41, 11 April 2008 (UTC)

Fiction = trivia?[edit]

The "heterosis in fiction" section reads a lot like a trivia section to me. Although I personally found it interesting, I question whether it is encyclopedic.204.97.106.20 21:38, 25 June 2007 (UTC)

Agreed. This section should be removed or moved to its own page in the Literature section. —Preceding unsigned comment added by 64.5.236.254 (talk) 12:29, 13 September 2007 (UTC)

No transcluding[edit]

Please note you should not transclude other articles into here. See Talk:Eurasian hybrid vigor#Removing my OR Nil Einne 08:51, 4 July 2007 (UTC)

Conflicting subordinate clauses[edit]

The clauses in this sentence cannot each be subordinate to the other:

"Although it is believed that heterosis is the action of many genes of small effect, whereas inbreeding depression is the action of a few genes of large effect."

Either the "although" or the "whereas" has to go. D021317c 09:49, 5 October 2007 (UTC)

Superior, better, fit[edit]

I have no objection to incorporating information about heterosis in humans, but whenever superiority or fitness are mentioned, whether in connection with humans or other organisms, it should be perfectly clear how an organism is "superior" or what it is more "fit" to achieve. There should never be a suggestion that one individual or lineage is categorically "better" than another, only that it may be better in a certain way, that is, at doing a certain thing. Otherwise, controversial value judgments (of Mr Spock, for example) may seem to be implied. D021317c 10:17, 5 October 2007 (UTC)

When Mr Spock (your example D0231317c) saves the starship and its crew from that TV episode's perilous situation by exercising his unique Vulcan mind merge ability it is "perfectly clear" to every trekie that he is the individual who is best at doing that thing. This is an example of fiction and is not a "controversial value judgement" that needs a finger-wagging warning to keep us politically correct. BTW whether you permit such a suggestion or not, evolution seems to have left a fossil trail of organisms (including some proto-humans) who were found "categorically" unfit to perpetuate their species. Cuddlyable3 20:15, 5 October 2007 (UTC)

Outbreeding depression[edit]

"It may also happen that a hybrid inherits such different traits from their parents that make them unfit for survival. This is known as outbreeding depression, typical examples of which are crosses between wild and hatchery fish that have incompatible adaptations."

It should be clarified that:

a) Outbreeding depression only occurs between populations that have diverged significantly i.e. Different species.

b) There are two kinds of outbreeding depression. One, because the hybrid isn't equally adapted to the parental environment. The other because of the breaking down of co-adapted gene complexes, especially in F2, F3 generations (e.g Bos Taurus x Bos Indicus).

Needs reconsideration[edit]

I removed this text:

Heterosis can be classified into mid-parent heterosis, in which the hybrid shows increased strength which is greater than the average of both parents, and best-parent heterosis, in which the hybrid's increased strength is greater than that of the strongest parent. Mid-parent heterosis is more common in nature, and it is easier to explain (by mechanism of gene dominance; see below).

The main objection is to the formulation the average of both parents. If that has any precise meaning(?) then by natural variation every offspring is very likely to have a strength that is above or below it. An anecdote that comes to mind is that President Eisenhower allegedly expressed outrage on hearing that 50% of american children have below-average IQ.Cuddlyable3 (talk) 17:50, 5 March 2008 (UTC)

I agree with your modification, actually have never heard of mid-parent heterosis or best-parent heterosis. The description of the concepts reminds me of the simpler concepts of dominance and over-dominance. --Crusio (talk) 18:19, 5 March 2008 (UTC)

Hybrid Corn section is misleading[edit]

The section title Hybrid Corn states that hybrid corn "was invented by Dr. William James Beal of Michigan State University based on work begun in 1879". This is misleading in the sense that all Maize ("Corn" in US usage) is a domesticate. The archaeological evidence indicates that the domestication took place in Mesoamerica at least 7500 years ago. There is a section in wikipedia detailing the origin of Maize that is (although not perfect) a good reference.

I think that this material could perhaps be either made more precise or removed? Does anyone have any thoughts on this? Guy.hunt (talk) 21:09, 19 March 2009 (UTC)

While I think it is probably a little ignorant to claim invention of a plant that owes the vast bulk of its evolutionary history to native peoples, I think the bigger omission in this article is its failure to mention the uselessness of the hybrid corns F-2 generation seeds. With farmers unable to reclaim their own seed, despite higher yields, hybrid corn effectively corporatized corn farming. This is a big part of agri-business today and it is foolhardy to gloss over it. 173.30.9.91 (talk) 06:52, 6 December 2010 (UTC)

Diversity per se?[edit]

I would like to edit the passage:

"The dominance hypothesis attributes the superiority of hybrids to the suppression of undesirable (deleterious) recessive alleles from one parent by dominant alleles from the other. It attributes the poor performance of inbred strains to the loss of genetic diversity, with the strains becoming purely homozygous deleterious alleles at many loci."

To instead read:

"The dominance hypothesis attributes the observed superiority of most hybrid offspring relative to their inbred parent strains to the suppression of undesirable (deleterious) recessive alleles. The hypothesis recognizes that the act of inbreeding causes genes to become "fixed" for a specific allele (they become homozygous across their various gene-loci). Further, it recognizes that individual inbred lines will differ in which specific alleles are fixed at any given locus. That is, where one inbred strain may be fixed for a "damaged" allele at a given locus, an independently inbred strain may have a healthy allele at that same locus. If the healthy allele is dominant relative to the "damaged" allele, offspring will have an advantage. Extend this concept across several genetic loci and it becomes clear that the hybrid might be superior to both of its inbred parents."

The important differences I have tried to convey are: 1.) Observed "vigor" of a hybrid is relative to its inbred parents; 2.) To be consistent with the dominance hypothesis, poor performance of inbred lines should not be attributed to a "loss of genetic diversity" but to the effects of deleterious recessive alleles fixed in the strain. An analogy of the dominance hypothesis is that the two inbred strains are like two junk cars and that it is possibel to build one good one from the parts of each. Who would argue that, for the sake of diversity, it would help to have one good starter and one bad?

Diversity is covered in the overdominance hypothesis.

So, I thought I would leave my suggestion here for now and see if anyone has any comments before I make the edit for real. Johnfravolda (talk) 22:35, 22 August 2010 (UTC)

Hi, this is certainly a deficient part of the page. Are you familiar with the "diversity per se" hypothesis which is really a third one? I've heard Jim Birchler speak about it, and it is difficult to lay out in a brief summary, too difficult for me to achieve, I think. The data to support it are convincing, but very subtle, and include experiments with specially constructed polyploids that are inbred or not.
I find what you've written quite a bit more complex than the original, and would argue that perhaps we do want simplicity in this article because our audience is likely to be mostly students working on assignments for high-school or early university. Unfortunately, without the third hypothesis, I don't see how to simplify this section. Nadiatalent (talk) 11:41, 23 August 2010 (UTC)
Yes, you are right about my version being too complex. Plus, it would be nice to cite someone as the originators of the ideas. I'll have to dig into my books a bit, and I will see what I can read from Birchler. Regarding the edit I had proposed, perhaps instead I can just change to "The dominance hypothesis attributes the superiority of hybrids (relative to their inbred parent strains) to the suppression of undesirable (deleterious) recessive alleles from one parent by dominant alleles from the other. It attributes the poor performance of inbred strains to the exposure of deliterious recessive alleles through the inbreeding process whereby most genetic loci become fixed in the homozygous state." —Preceding unsigned comment added by Johnfravolda (talkcontribs) 14:37, 23 August 2010 (UTC)

References vs Further reading[edit]

I moved several "references" to the Further reading section, because they are practically worthless as references without wp:in-line citations to you can trace them to corresponding claims in the article. If you can match any of them to its claim, please link it with wp:in-line citation format as done with current references. Mikael Häggström (talk) 17:51, 30 September 2011 (UTC)

Merges to Heterosis[edit]

From Heterotic group[edit]

Seems to more appropriately constitute a "In plant breeding"-section in the Heterosis article. Mikael Häggström (talk) 06:04, 2 October 2011 (UTC)

It's merged now. Mikael Häggström (talk) 09:36, 4 October 2011 (UTC)

From Dominance versus overdominance[edit]

Seems to completely describe Heterosis#Genetic basis of heterosis, and neither article is long enough to motivate forking this topic away from the Heterosis article, and neither does the number of what-links-here for Dominance versus overdominance. Mikael Häggström (talk) 06:04, 2 October 2011 (UTC)

Mules[edit]

A clearly ambiguous counter-example to any value judgement on hybrids and hybrid vigor is the mule. While mules are almost always infertile, they are valued for a combination of hardiness and temperament that is different from either of their horse or donkey parents. While these qualities may make them "superior" for particular uses by humans, the infertility issue implies that these animals would most likely become extinct without the intervention of humans through animal husbandry, making them "inferior" in terms of natural selection.

I'm not sure why we have a "clearly ambiguous" example here which obviously describes something that would never happen in nature (i.e., cross-species breeding). I'm going to axe this, unless someone has a compelling reason it should stay. Graft | talk 21:36, 13 June 2013 (UTC)

I think it is useful to leave that discussion on the page because it relates to a point on which there is much confusion. Sminthopsis84 (talk) 23:31, 13 June 2013 (UTC)
How is it useful? It just adds to the confusion. There is already a mention of outbreeding depression, which is the relevant point. A completely human-created hybrid is hardly relevant to discussions of hybrids and fitness. Graft | talk 15:15, 14 June 2013 (UTC)
Mules are a point of accessibility for the article. Lots of people know of them. Many people wonder why they are created and whether they are unfortunate accidents that result from humans keeping horses and donkeys together. Whether hybrids are inferior or superior is a question that potentially makes people read the heterosis article, and being referred to mules as relevant is appropriate. Sminthopsis84 (talk) 15:39, 14 June 2013 (UTC)
However, heterosis is about heterogeneity within a breeding population, which does not describe mules. I think introducing the notion of a mule as a "hybrid" will confuse people further. The "hybrid" in "hybrid vigor" does not describe the mule, it describes the highly-heterozygous individual who carries most of the common variants of the breeding population. A cross-species "hybrid" is not a good example to introduce here. Graft | talk 16:22, 14 June 2013 (UTC)
No, heterosis is not about heterogeneity within a breeding population, it can be a significant factor within a single individual. See for example [1]. A cross-species hybrid is an excellent example of heterosis. Sminthopsis84 (talk) 17:25, 14 June 2013 (UTC)
Heterosis is a property of individuals, but the vigor it produces is a result of the expression of common variation in a breeding population. Since improved yield is one of the hallmarks of heterosis in plant species, I think it is an error to discuss mules, which literally have zero fitness, in this context. At the very least, can we reform the paragraph to use them as an example of outbreeding depression? That makes much more sense to me. Graft | talk 23:08, 15 June 2013 (UTC)
There's a page on Outbreeding depression, would that really belong here as well? I disagree that "the vigor it produces is a result of the expression of common variation in a breeding population", or rather that it is only that. Heterosis can occur in a single offspring of an inter-species cross, or even from genetic engineering in one individual. Sminthopsis84 (talk) 20:21, 16 June 2013 (UTC)

Anthropology, Human Biology, and Race Citations Bibliography for Use in Updating Articles[edit]

You may find it helpful while reading or editing articles to look at a bibliography of Anthropology and Human Biology Citations, posted for the use of all Wikipedians who have occasion to edit articles on human genetics and related issues. I happen to have circulating access to a huge academic research library system at a university with an active research program in these issues (and to other academic libraries in the same large metropolitan area) and have been researching these issues sporadically since 1989. You are welcome to use these citations for your own research. You can help other Wikipedians by suggesting new sources through comments on that page. It will be extremely helpful for articles on human genetics to edit them according to the Wikipedia standards for reliable sources for medicine-related articles, as it is important to get these issues as well verified as possible. -- WeijiBaikeBianji (talk, how I edit) 17:09, 19 July 2013 (UTC)

Cannabis[edit]

Given all hybrid cannabis is for use as a drug and the reasoning behind it is to increase the potency of cannabis as a drug (ie its not used in hemp) it makes sense to link to the drug article as well as the plant article, and I have now done so. By all means re-word what I say but please dont remove the link to the drug article. ♫ SqueakBox talk contribs 15:20, 12 January 2014 (UTC)