Hybrids vulnerable to bad genes?

[Spetulhu]

I've run into a strange racial supremacist troll on a local BBS. "I'm not a racist, but other races shouldn't come here" and "I'm no nazi, but racial hygiene is a good thing" seems to be the agenda. She's come up with a new term, "the hybrid effect", and claims this as proof that mixing races is bad. Apparently this effect makes mixed-race offspring more vulnerable to hereditary defects than their pure-blooded cousins as bad genes are more likely to meet!

Does anyone else find this thinking flawed? And where does it come from?

[Lord of the Abyss]

Well, crossbreeding species often creates sterile individuals, like mules. There also be genetic incompatibilities between individuals, like a person with a big jaw and big teeth having kids with someone with a small jaw and small teeth. The result can be someone with big teeth and a small jaw, and nasty dental problems.

Assuming he's not just making it up, that's where he's probably getting the idea.

OTOH, there is "hybrid vigor", where crossbreeds are bigger and stronger than the "pure" strains. Also, there's far less chance of manifesting recessive genes if you outbreed.

Note that none of this has anything to do with "races", which are pretty much imaginary. It may be important with individuals, and is important between species, but not between races.

[Stile]

+http://newsinfo.iu.edu/news/page/normal/1065.html

Cross-species mating may be evolutionarily important and lead to rapid change, say IUB researchers

Like the snap of a clothespin, the sudden mixing of closely related species may occasionally provide the energy to impel rapid evolutionary change, according to a new report by researchers from Indiana University Bloomington and three other institutions. Their paper was made available online by Science magazine's "Science Express" service today (August 7) at 2 p.m. EDT.

A study of sunflower species that began 15 years ago shows that the sudden mixing and matching of different species' genes can create genetic super-combinations that are considerably more advantageous to the survival and reproduction of their owners than the gene combinations their parents possess.

"This is the clearest evidence to date that hybridization can be evolutionarily important," said IUB biologist Loren Rieseberg, who led the research. "What's more, we were able to demonstrate a possible mechanism for rapid evolutionary change by replicating the births of three unusual and ecologically divergent species within an extremely short period of time -- just a few generations."

The finding comes a month after IUB biologist Jeffrey Palmer and colleagues suggested in a letter to Nature that genetic exchange between completely unrelated species has occurred more often than experts previously thought.

There are many modern examples of hybridization in nature, some forced, some natural. Mules are bred by humans from horses and donkeys, are completely sterile, and represent an evolutionary dead-end. But there are other species-crossings that do just fine, such as offspring of the notoriously promiscuous oak tree species, which hybridize so often species-namers commonly joke about not being able to keep up.

Still, cross-species matings usually result in sickness or sterility, if the offspring get that far -- many naturally abort. Hybrid offspring that are fertile but sick or weak will not be able to compete with the purer offspring of either parent in passing on their genes to future generations. As a result, many evolutionary biologists have thought hybridization to be evolutionarily unimportant.

But Rieseberg's new report suggests that even weak, hybrid offspring can acquire new, strong combinations of genes from their parents. As long as those offspring are just virile enough to transmit their useful genes to their own offspring, those genes may fight their way into populations of either or both parent species and become evolutionarily important. Hybridization has been used to great effect in the creation of successful crops and animal breeds, but many evolutionary biologists have resisted accepting hybridization's importance in a world before the appearance of modern humans.

"We're all aware hybridization and intensive cross-breeding has produced better corn and better cows," Rieseberg said. "Yet there's been resistance in the evolutionary biology community to the notion that evolution might sometimes be facilitated by hybridization."

Rieseberg and his team compared the physical, physiological and genetic traits of several sunflower species. Two of the species, Helianthus annuus and H. petiolaris, are considered "parental," or more ancient. Another three species the scientists studied, H. anomalus, H. deserticola and H. paradoxus, are believed to have evolved somewhat recently, as hybrids of the two parental sunflower species, between 60,000 and 200,000 years ago. The three hybrid species are remarkable in being adapted to very extreme habitats: sand dunes, dry desert floor and salt marshes, respectively. The researchers also created their own hybrids of H. annuus and H. petiolaris.

The researchers found that their synthetic hybrids quickly acquired the traits necessary to colonize the extreme habitats of their naturally evolved hybrid counterparts, suggesting that potentially useful traits can be created quickly. Rieseberg and his team also found that the traits were largely the same as those produced by natural selection during the evolution of the natural hybrid species. Through cross-breeding, the researchers were able to simulate the birth of three new species and the large and dramatic evolutionary changes that accompanied their origins.

"It's often very easy to explain small differences we see within a species, but harder to account for larger differences between species that require changes in multiple traits or genes," Rieseberg said. "We have provided an explanation for how some of these more difficult changes might happen. Dramatic evolutionary changes are most likely to occur when parental species are very different from each other, creating a much broader array of gene and trait combinations."

Researchers at La Laboratoire de Biologie Moleculaire et Phytochimie (Villeurbanne, France), the University of Georgia and Kent State University also contributed to the report. It was funded by grants from the National Institutes of Health and the National Science Foundation.

To speak with Rieseberg or to receive high resolution photos related to the research, contact David Bricker at 812-856-9035 or brickerd@indiana.edu.

As the study stated, usually hybrids are sterile or not as robust as their forebearers and that may be why racists have that opinion.

Also, the problem with this attitude is that hybridization is crossbreeding between species and not races.

I would postulate that inter-racial marriage causes genetic diversity and decreases hereditary defects because of less likelyhood of a recessive gene for something like cyctic fibrosis.

Besides, some races aren't easily defined in some areas. Take a look at Brazil for example.

[dworkin]

It's the complete opposite of your troll's assertion. Breeding outside your deme (local population group) is a good thing. It breaks up lethal allele combinations resulting in healthier, longer lived people. They tend to look better too.

The human raceial differences are based on skewed allele ratios in each particular deme. As an example, northern Europeans have a disproportionate proportion of alleles for blonde hair. But lethal genes come in clumps in each deme as well, the most well documented being sickle-cell aneamia. While breeding outside your deme means your children might well pick up some new lethals the fact that most lethals are recessive means that they won't be phenotypically expressed (they won't cause the disease). Such a child will only have half the lethals from each parent. Successive generations are also unlikely to result in lethal homozygosity.

The troll's ideas are directly based of eugenics, the science of breeding a better human in the same way people bred better roses and poodles. It was seen as a marvelous new way to improve humanity. It was very popular in Europe and the U.S. However the labeling of racial groups as possessing 'undesirable traits' meant the 'science' was pretty much doomed to unworkability. Eugenics ended up being the newest justification for racial and class segregation. Most racist pseudoscientific rationales for their idiocy date from the eugenics programs of the early 20th century as does I.Q. testing.

Of course the revelation of what the Nazis had done with their eugenics programs pretty much damned the idea in perpetuality.

[Nephtys]

Em. There's a good deal of difference between human 'races' and 'species'. Races are more or less a social construction rather than strict biology, and are genetically just variations of the same set of combinations. Species meanwhile, have actual differences that prevent reproduction and the like.

The black guy down the street has the same DNA as the white guy next door, and the asian across the way, just with different expression, and traits given by their parents. A diverse gene pool offered by many human 'races' is a good thing, because it provides Diversity, which is what keeps our species alive.

Meanwhile, inbreeding within populations tends to cause more common occurences of the same traits. Symmetry tends to lead to bad things.

[wolveraptor]

It's almost comical that the reality of the situation is the exact opposite of what the troll declaims. As many of the above posters have said, more you stay with in a confined population, the more likely you'll meet a carrier of the same recessive genetic defect as you. The probability of you having a child with said faulty gene from both parents is greatly increased.

[Admiral Valdemar]

Point out that races don't exist. If she attacks that point, ask her to give evidence of the major differences between a Caucasian and an African.

After she's put her foot in her mouth again, start asking what colour hair she has. Then start discriminating against it. We can't have gingers, for instance, breeding with pure blondes. That'll destroy the species.

[wolveraptor]

...ask her to give evidence of the major differences between a Caucasian and an African.

She'll say skin color, obviously. She can also point out that there are certain genetic defects found only in Africans, and that such clumping of specific diseases shouldn't occur if there is no race.

[Admiral Valdemar]

There are just as many defects in Caucasians, and given high melanin concentration in the skin wards off cancer and sunstroke in tropical climates, that's an advantage.

[Surlethe]

...ask her to give evidence of the major differences between a Caucasian and an African.

She'll say skin color, obviously. She can also point out that there are certain genetic defects found only in Africans, and that such clumping of specific diseases shouldn't occur if there is no race.

Just how major are those differences?

[Nephtys]

...ask her to give evidence of the major differences between a Caucasian and an African.

She'll say skin color, obviously. She can also point out that there are certain genetic defects found only in Africans, and that such clumping of specific diseases shouldn't occur if there is no race.

Just how major are those differences?

Those 'african defects' are most notably sickle-cell anemia, a condition which is just from a trait in higher concentration in Africans, because it's a beneficial one due to malaria being commonplace.

Skin color is not an issue. It's about gene expression, and pigment is created. Nothing like the structural differences between us and chimps, or various other things.

Try proposing this then. If your mom is redheaded, and your dad black haired, and you are born with a different color hair due to recessive traits or partial expression... are you a different 'race' than them? Hell no.

[wolveraptor]

There are just as many defects in Caucasians, and given high melanin concentration in the skin wards off cancer and sunstroke in tropical climates, that's an advantage.

Irrelevant. I wasn't making any point about which race is genetically superior in terms of disease frequency. I was just saying that such constancy of sickle-cell anemia in one particular skin-color might point to some sort of real, scientific grouping.

[Nephtys]

There are just as many defects in Caucasians, and given high melanin concentration in the skin wards off cancer and sunstroke in tropical climates, that's an advantage.

Irrelevant. I wasn't making any point about which race is genetically superior in terms of disease frequency. I was just saying that such constancy of sickle-cell anemia in one particular skin-color might point to some sort of real, scientific grouping.

It's not a genetic difference due to race. It's something that's more common due to the environmental conditions. Following this example, in Europe, Malaria is uncommon, so anemia is a detriment. Thus, people with it tend to die and the gene is not spread as frequently. It's still around. Meanwhile in africa, it's the lesser of two evils. It's better to have sickle-cell anemia than to get malaria and die. So it's thus more common.

Absolutely nothing to do with racial genetics being inherently different.

[wolveraptor]

You don't think that the two populations existing independently might diverge somewhat to create the characteristics you're talking about? I'm making the point that environmental conditions can cause the furcation of human demographics into distinct groupings: races.

[Nephtys]

You don't think that the two populations existing independently might diverge somewhat to create the characteristics you're talking about? I'm making the point that environmental conditions can cause the furcation of human demographics into distinct groupings: races.

Over the timespan they've been isolated? Nope. The term 'race' biologically doesn't mean a thing. It's social. Species is the basic foundation of differentiating kinds of organisms, and we're certainly different species.

The characteristics were always with us, as a part of the possibilities that can be expressed as Homo Sapiens. It's just in higher concentration in areas where such would be most beneficial.

[wolveraptor]

So you admit that the liklihood of sickle-cell anemia is higher among those of African descent, but you don't this creates any sort of grouping? Mind you, I'm not talking about speciation at all, just loose convocation.

[Nephtys]

So you admit that the liklihood of sickle-cell anemia is higher among those of African descent, but you don't this creates any sort of grouping? Mind you, I'm not talking about speciation at all, just loose convocation.

Why should it create grouping? Of course some groups exist. We call them 'races', for those people who express similar traits due to being traditionally from a certain region. What are you getting at?

[Adrian Laguna]

Over the timespan they've been isolated? Nope. The term 'race' biologically doesn't mean a thing. It's social. Species is the basic foundation of differentiating kinds of organisms, and we're certainly different species.

Actually, the term "race" or "breed" does have meaning in biology. It just doesn't apply to humans. The most known examples of species that have recognized races are Equus caballus (horses) and Cannis lupus (wolves and dogs).

[Adrian Laguna]

Ghetto Edit - Come to think of it, I might have some things messed-up. I might have been thinking of the term subspecies. In which case horses don't apply. The dogs/wolves example does hold-up. As wolves are C. lupus, while dogs are C. l. familiaris.

[Spetulhu]

After she's put her foot in her mouth again, start asking what colour hair she has. Then start discriminating against it. We can't have gingers, for instance, breeding with pure blondes. That'll destroy the species.

Funny enough, it's this "destroying the species" she's going for. You see, it'll upset the natural order if you mix races. She started the whole debacle by complaining about how our Western governments force people to mix since discrimination based on race is a social taboo. Soon there will be no more distinct groups! We are meddling with nature by allowing this!

Heh. I thought it was natural to breed?

[wolveraptor]

What are you getting at?

This:

Of course some groups exist. We call them 'races', for those people who express similar traits due to being traditionally from a certain region.

That's the only point I was trying to make. It was in response to the following:

...ask her to give evidence of the major differences between a Caucasian and an African.

Obviously, there are some recognizeable differences between Caucasians and Africans. If these are not considered a "major" differences, then I withdraw any objection to the preceding statement.

[Nephtys]

What are you getting at?

This:

Of course some groups exist. We call them 'races', for those people who express similar traits due to being traditionally from a certain region.

That's the only point I was trying to make. It was in response to the following:

...ask her to give evidence of the major differences between a Caucasian and an African.

Obviously, there are some recognizeable differences between Caucasians and Africans. If these are not considered a "major" differences, then I withdraw any objection to the preceding statement.

They're certainly not major differences, as these traits are found in all populations. There's just more common occurences of the same minor differences. So alright.

[wolveraptor]

Thanks to whoever fixed my quotes.

[RedImperator]

You don't think that the two populations existing independently might diverge somewhat to create the characteristics you're talking about? I'm making the point that environmental conditions can cause the furcation of human demographics into distinct groupings: races.

It's theoretically possible, but it hasn't actually happened in H. sapiens. People get tripped up on skin color because it's visually very obvious, but it's actually a fairly minor trait. Besides that, skin color varies widely within the "races"; most South Asians I've met have skin as dark or darker than many Africans, but in the racial classification system, South Asians are considered "white".

The concept of race among humans was basically invented by Europeans in the 16th and 17th centuries to explain how they conquered the world and to justify their own barbaric behavior. They looked at the rest of the world, and concluded that since they'd kicked the asses of everyone who lived there, Europeans must be a superior type of human. Skin color was siezed upon as an obvious outward marker of racial type, but if every human on Earth shared the same skin tone, they would have found something else.

[wolveraptor]

Who the hell considers South Asians white? Also, as I pointed out earlier, the fact that the frequencies of certain alleles are much higher in certain demographics than others, we might yet find that there is some loose scientific backing to the idea that populations in certain areas have slightly diverged to form the misnomer that is a race.