The Gaming Den

This could probably be a PM but I guess someone other than Frank might be able to answer this question.

I remember reading in a topic about racism that cats had more genetic diversity between members of the same litter than two random human beings. My search-fu is weak and I can't seem to find that damned quote.

I'm fighting racists on another board and I'm trying to illustrate very simply (they are not very intelligent) that human genetic diversity is very limited, and a source for this exact information would really be handy at the moment.

Anyone got anything for me there ? This is for the greater good after all.

That's a pretty cool article, but I really want the cat proof. That's the kind of simple example that ought to shut them up

Dunno about cats - though I think I saw that cheetahs have ridiculously low genetic diversity in SciAm once - but it's easy enough to find articles about chimps genetic diversity online, and they are much more diverse than humans. Just google chimpanzee genetic diversity.

Were you thinking about this line of Frank's?

I leave you with the following sobering concept: go find a squirrel nest and grab two of the baby squirrels. Holding two sister squirrels in your hand, you have more genetic variation than between you and a random person of the opposite sex in Ghana.

This is the closest more official thing I can find with a quick Googling.

there is substantially more genetic difference among individuals within chimpanzee troops in West Africa than among all living humans on earth.

What genetic diversity is, is the amount of DNA different between one member of the species and another. So the genetic diversity between twins is always effectively zero. Actually, it's the base mutation rate for he species, bt that's effectively zero. Indeed, for the purpose of this discussion we can virtually ignore the single-generation mutation rate, because it cancels out in most mammals anyway.

House cats born in the same litter are not clones in the way that twins are. They get a separate egg from the mother and sperm from the father. Each of hose gametes is loaded with a random assortment of half the genetic code of the parent. The genetic code is pretty big, so it's generally large enough that you can predict it to split fairly evenly. Thus, two siblings share half of their genetics over and above the genetic diversity of their species. That is to say, on average they will have gotten half of the mother's contribution and half of the father's genetic contribution the same. So their total genetics are 1/4 identical maternal DNA, 1/4 identical paternal DNA, 1/4 other maternal DNA, and 1/4 other paternal DNA.

Parts of the half of the DNA that was the "other" is still going to end up the same, or at least very similar in a lot of cases. Because there is a lot of homozygosity in the world - DNA that is the same in both copies so it doesn't matter which copy you get. But basically what you are looking at with litter mates is a total genetic diversity between them that is half the genetic diversity between two random individuals in the general population.

Humans have a very low genetic diversity. Not as bad as the "every family except one died 10,000 years ago" Cheetahs, but pretty damn bad. We have a long generation time, and a bottleneck something like 150,000 years ago. As it happens, we bred the domestic house cat around 100,000 years ago, but they have a generation time is an order of magnitude faster - so they have accumulated a lot more diversity since then than we have. More than twice as much.

So if you take the genetic diversity in just the half of the DNA that is not the same in litter mates of domestic cats, you still get more genetic diversity for the whole organisms than you get from grabbing two random people from Africa and Europe.

As for racism against "Black" people specifically, it makes even less sense. There is more genetic diversity in Africa than there is in the rest of the world. That is to say that if you were going to divide up humans genetically, you'd have more groups of Black people than all others combined. As in seriously, fourteen African ancestral populations and like one for Asians, Europeans, and Native Americans. I think the Aboriginals of Australia and Oceania might get one too.

-Username17

It's not just black people.

There's a guy around college who swears Arabic people are subhuman, don't deserve to rule anything, are inherently violent, etc. The term 'raghead' comes up often when he gets going.

I know skin tone is based on melanin production which is influenced by vitamin D and some other factors...

Just wish someone could make him understand that science behind 'race'.

you know... I know better, but I almost (almost) agreed with him... but with me it's because of culture, not race. I mean, hell, I'm tempted to think similar things about christians...

Prak_Anima wrote:you know... I know better, but I almost (almost) agreed with him... but with me it's because of culture, not race. I mean, hell, I'm tempted to think similar things about christians...

I'm down with saying there's a cultural aspect there. But it's basically nationalism and distrust of the West (can't say I blame them. European/Western culture has an extremely shitty past when it came to people who happen to be anything other than really white.)

But he says it's because they're 'ragheads'.

When I pointed out the long and convoluted history of ethnic strife in the Balkans, he said, "yes, but I assume these people are white."

He really does think there's inherent worthiness attached to skin color which determines...something or other.

People tend to get him to shut up before he gets much further than that.

I don't think that the degree of difference matters to racists. The power is in the idea that differences exist, and that they're important. Racism thrives on the combination of cosmetic categorization and the confirmation bias, couched in an unshakable basis of logical contradiction.

There's a guy around college who swears Arabic people are subhuman, don't deserve to rule anything, are inherently violent, etc. The term 'raghead' comes up often when he gets going.

Arabs? Arabs are white people. Seriously, you know who is an Arab? Shakira. She's a Lebanese Columbian. That's what Arabs look like.

You know how some people have blue eyes? That's from Syria. And fairly recently at that. If you or anyone you know has blue eyes, it's because their family members fucked an Arab. Twice.

Because blue eyes is recessive.

-Username17

FrankTrollman wrote:
Arabs? Arabs are white people. Seriously, you know who is an Arab? Shakira. She's a Lebanese Columbian. That's what Arabs look like.

You know how some people have blue eyes? That's from Syria. And fairly recently at that. If you or anyone you know has blue eyes, it's because their family members fucked an Arab. Twice.

Because blue eyes is recessive.

-Username17

Frank, you just made my day. He has blue eyes.

FrankTrollman wrote:She's a Lebanese Columbian.

So why does she sound like Celine Dion?

Orca wrote:Dunno about cats - though I think I saw that cheetahs have ridiculously low genetic diversity in SciAm once - but it's easy enough to find articles about chimps genetic diversity online, and they are much more diverse than humans. Just google chimpanzee genetic diversity.

I remember Frank saying something about that once; that it would take very little to wipe them off the face of the earth because of it.

FrankTrollman wrote:Humans have a very low genetic diversity. Not as bad as the "every family except one died 10,000 years ago" Cheetahs, but pretty damn bad. We have a long generation time, and a bottleneck something like 150,000 years ago. As it happens, we bred the domestic house cat around 100,000 years ago, but they have a generation time is an order of magnitude faster - so they have accumulated a lot more diversity since then than we have. More than twice as much.

What do you mean by a "bottle neck"? You mean something that limited the gene pool (i.e. killed off all the "different" humans)?

What do you mean by a "bottle neck"? You mean something that limited the gene pool (i.e. killed off all the "different" humans)?

A bottleneck is a point where the genetic variation got limited. Traditionally yes, by the systematic killing of every single example with different genes from the population. In fact, that's pretty much always how it works (barring some fairly unlikely genetic drift events).

But it doesn't have to happen all at once or anything. Genetically speaking, anything that ever gets wiped out may as well have terminated at the point it diverged from the remaining population. Imagine for example, a population dividing: all the gingers go live on one island and everyone else goes to live on the other - then a thousand, or a million years later the island with all the gingers on it sinks into the sea. The remaining population would have lost all its gingers years ago, which is where the last bottleneck would be counted from.

So humanity as we know it today came from a very small gene pool quite some time back. All humans on Earth have the same mother if you go back 200,000 years or so, and all living men can trace their heritage to a single man some 80,000 years back. But there were still totally other groups of essentially humans for tens of thousands of years after that. Neanderthals (orcs) lived until like 30,000 years ago, and Florensis (Halflings) were around until like 13,000 years ago. But none of them are alive today, so our relative bottleneck s counted from when all of that genetic variation in hominids went off and did their own thing.

-Username17

as it is gingers are "dying out" (really more of breeding out, from what I understand), and within a generation or two there really won't be any more pale skinned red headed kids wandering around.

Is that recessive, or something?

Prak_Anima wrote:as it is gingers are "dying out" (really more of breeding out, from what I understand), and within a generation or two there really won't be any more pale skinned red headed kids wandering around.

Red hair is a dominant trait, so some day we'll be overrun with them.

K wrote:

Prak_Anima wrote:as it is gingers are "dying out" (really more of breeding out, from what I understand), and within a generation or two there really won't be any more pale skinned red headed kids wandering around.

Red hair is a dominant trait, so some day we'll be overrun with them.

That's not what wikipedia says.

Biochemistry and genetics

The pigment pheomelanin gives red hair its distinctive colour. Red hair has far more pheomelanin than other hair colours, but far less of the dark pigment eumelanin.

The genetics of red hair, discovered in 1997, appears to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16. Red hair is associated with fair skin colour due to low concentrations of eumelanin. This lower melanin-concentration has the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions. However, when the UV-radiation is strong (like in the regions close to the equator) the lower concentration of melanin leads to several medical disadvantages; one of them is the higher rate of skin cancer.

The MC1R recessive variant gene, which gives people red hair and fair skin, is also associated with freckles, though it is not uncommon to see a redhead without freckles. Eighty percent of redheads have an MC1R gene variant,[4] and the prevalence of these alleles is highest in Scotland and Ireland. The alleles that code for red hair occur close to the alleles that affect skin colour, so it seems that the phenotypic expression for lighter skin and red hair are interrelated.

Red hair can originate from several different changes on the MC1R-gene. If one of these changes is present on both chromosomes then the respective individual is likely to have red hair. This type of inheritance is described as an autosomal recessive mode of inheritance. Even if both parents do not have red hair themselves, both can be carriers for the gene and have a redheaded child. (red hair genetics).

Recessive traits don't die out though, they just don't get expressed unless you have two copies of them. So if you have two people with one copy of it, you can still get someone with two copies if they have kids.

A classic example is the gene that causes sickle cell anemia. With two copies, you get sickle cell anemia. With one copy, you get malaria resistance. It only kills you off if you get both copies (or not even that since we can treat it somewhat), so it's never going away-the people with just one copy have a greater chance of surviving and spreading the recessive gene, and bad stuff only happens when children are borne with both copies. But since having both copies makes living very difficult, you'll never see everyone in the world running around with two copies, and so even if everyone in the world had one, only one in four (roughly, may vary depending on if it's 2x2 or 4x4 or whatever) kids end up with sickle cell anemia.

Of course, a better way to go about giving the people of the third world malaria resistance is just to give them mosquito nets, which is really cheap to do.

FrankTrollman wrote:

There's a guy around college who swears Arabic people are subhuman, don't deserve to rule anything, are inherently violent, etc. The term 'raghead' comes up often when he gets going.

Arabs? Arabs are white people. Seriously, you know who is an Arab? Shakira. She's a Lebanese Columbian. That's what Arabs look like.

You know how some people have blue eyes? That's from Syria. And fairly recently at that. If you or anyone you know has blue eyes, it's because their family members fucked an Arab. Twice.

Because blue eyes is recessive.

That was awesome.

Sir Neil wrote:So why does she sound like Celine Dion?

You have no ears.

RobbyPants wrote:

K wrote:

Prak_Anima wrote:as it is gingers are "dying out" (really more of breeding out, from what I understand), and within a generation or two there really won't be any more pale skinned red headed kids wandering around.

Red hair is a dominant trait, so some day we'll be overrun with them.

That's not what wikipedia says.

Not to be one to argue with Wikipedia, here is a more complete section explaining the issue. Sections bolded by me.

In general, hair color is determined by multiple genes and the inheritance of hair color is complex and not yet completely understood. However, red hair is known to be associated with specific variations in the MC1R gene.

Several MC1R variants have been shown to have strong associations with red hair (and pale skin). Most people with red hair have two copies of the same "red hair variant" or two copies of different "red hair variants." People with one copy of a "red hair variant" and one copy of a "non-red hair variant" are called carriers and typically do not have red hair. As such, red hair is often said to have autosomal recessive inheritance.

Other genetic variations also likely play a role in determining red hair color.

This means that there are people with one copy of the variant gene who are expressing red hair, thus meeting the criteria of "dominant." That this is uncommon, and that several other variants produce red hair only with two copies means that overall, the classification is kinda meaningless.

The truth is that Mendelian genetics doesn't have a term for "in the current population this trait is sometimes dominant with one copy, most of the time recessive with one copy, and if the population changed it might be reversed as different sets of genes that can express this trait become more common."

Whether they will become the way of the future is debatable. Red heads were killed at birth in the UK for centuries and the various gene variants survived, so my guess is that there is some systematic reason they survive and flourish despite negative selection.

The take-away lesson is that the language of Mendelian genetics doesn't work that well when applied to modern understandings of complex organism genetics and not pea plants.

Ah ha. Thanks for the clarification.

One reason is that red hair at birth isn't completely co-related with red hair at adulthood, and other peasants didn't practice this, despite being under English rule.

Mendelian genetics only work for basic understanding. Then we realize that there are sometimes yet more 'dormant' genes interact in huge matrixes, rather than simple pairs.

-Crissa

Gene interactions can be pretty complex. e.g. we can be fairly sure that Mendel faked at least some of his data, because even the simple genes he was tracking when he was breeding peas don't split quite as evenly as his data showed.