The spread of recessive biological traits via sexual selection.

[Dinner]

I'm interested in what people think of this theory I've been reading. It is designed to explain the spread of recessive genetic traits (examples: blue & green eyes or blond & red hair) which would normally be drowned out by dominate genetic traits (brown eyes or darker hair) in a population which was free to interbreed. The basic theory goes that areas which have few resources, like ancient northern Europe, but are still sufficiently technologically advanced (agriculture, etc) to allow social stratification then an elite will end up dominating society and have greater chances to reproduce.

For instance rich people, nobles, could afford to marry young and to attract the most attractive/youngest mates while the poor would have to wait until they are older before they could afford to marry. This would naturally result in the rich having more children because they have more years available to reproduce. So if the most successful members of society were preferentially selecting traits they find sexually attractive then those traits would quickly spread even if they were recessive instead of dominate traits.

The question is does this theory hold up to critical examination or is it bollucks?

[LordShiva]

All else being equal, a male with teh recessive trait might prefer a female with teh recessive trait so that he could know for sure that he isn't teh dad if teh kid ends up having teh dominant trait.

[Dinner]

Hadn't thought of that.

[Elok]

I thought it was just that novelty is sexually attractive. If you stand out from the crowd in a way that isn't completely hideous, you're likely to attract more attention than the people who look exactly the same as each other. That puts the gene in the population, and when two people with the recessives have kids, bingo! That person in turn is more attractive, and the gene spreads still further. The recessive nature of the gene keeps it a minority and thus still attractive. Something like that.

Oh, and even today the poor outbreed the rich. Today it's the result of many factors (including ignorance/dislike of birth control), but in premodern times it was a far more marked distinction. Farmers can always use kids to help them tend the crops, and before modern child-labor laws they could be sent off to the mills for extra income. Whereas rich kids just spend their parents' money on education, clothes, food and baubles. They can be married off to create alliances with other families but otherwise they're not much practical use.

[lord of the mark]

is blonde hair recessive? I thought hair color was determined by multiple genes?

Why would a recessive gene thats not evolutionarily disadvantageous be "drowned out"? Clearly the phenotype would show up less frequently then the gene, but sheer chance would mean that the phenotype would be expressed, depending on the frequency of the gene.

And I thought it was widely believed that lighter coloration, less melatonin, to which blue eyes and blond hair are physically linked, is advantgeous in cold climates (vitamin D and all that)

Whats much more interesting is how clearly disadvantgeous recessive genes, ones that cause fatal diseases, survive. The candidates, IIUC, are genetic drift (sheer chance from a small founder population) versus heterozygote advantage (its good to be a carrier - the classic example is Sickle Cell Anemia and its relation to malaria - a more controversial theory (not widely accepted) is Cochrans views on Tay Sachs and other lipid/neurological conditions and Ashkenazi intelligence)

[Dinner]

I think today, or even in the middle ages, society is rich enough were just about everyone can afford to marry young if they so choose. I'm thinking about the period between 20k BC and to around 0 AD. During those times there wasn't much of an agricultural surplus so the advantages of being a wealthy land owner or lord were so pronounced that they might mean the difference between eating or not eating. Thus the pull of wealth was far more pronounced.

[Japher]

For instance rich people, nobles, could afford to marry young and to attract the most attractive/youngest mates while the poor would have to wait until they are older before they could afford to marry. This would naturally result in the rich having more children because they have more years available to reproduce. So if the most successful members of society were preferentially selecting traits they find sexually attractive then those traits would quickly spread even if they were recessive instead of dominate traits.

Didn't the exact opposite generally incur? Poor people had more kids to work the land/earn the bread to help with the family? Doesn't it still happen today? Poor people have more kids to get bigger welfare checks?

I think the theory is backwards. Rich people will have less kids because of inbreeding and greed.

[lord of the mark]

Originally posted by Elok
I thought it was just that novelty is sexually attractive. If you stand out from the crowd in a way that isn't completely hideous, you're likely to attract more attention than the people who look exactly the same as each other. That puts the gene in the population, and when two people with the recessives have kids, bingo! That person in turn is more attractive, and the gene spreads still further. The recessive nature of the gene keeps it a minority and thus still attractive. Something like that.

Oh, and even today the poor outbreed the rich. Today it's the result of many factors (including ignorance/dislike of birth control), but in premodern times it was a far more marked distinction. Farmers can always use kids to help them tend the crops, and before modern child-labor laws they could be sent off to the mills for extra income. Whereas rich kids just spend their parents' money on education, clothes, food and baubles. They can be married off to create alliances with other families but otherwise they're not much practical use.

In pre-industrial society starvation, disease, etc meant most children of poor folks didnt survive. General population growth was slow. Its possible the richest peasants/yeoman farmers outbred the aristos(though Im not sure of that), but I very much doubt the poor peasants/landless laborers came close to keeping up with the better off farmers.

[Spec]

Originally posted by Japher
I think the theory is backwards. Rich people will have less kids because of inbreeding and greed.

You read my mind.

Rich people can afford electricity, hence, they have other things to do at night.

Spec.

[lord of the mark]

Originally posted by Spec


You read my mind.

Rich people can afford electricity, hence, they have other things to do at night.

Spec.

gads, people are misreading Oerdin. hes not talking about the last 200 years folks.

During most of human history, for most people, there was certainly a postive correlation between wealth and number of children who survive long enough to breed.

[Dinner]

LotM, yes the phenotype would still exist but would rarely be manifested. The question is how do we explain locations were the recessive trait is the dominate trait? Is it just founder effect? If so then how did the initial mutation spread? Assuming the blue or green eye mutation started with just one person.

[lord of the mark]

Originally posted by Oerdin
I think today, or even in the middle ages, society is rich enough were just about everyone can afford to marry young if they so choose. I'm thinking about the period between 20k BC and to around 0 AD. During those times there wasn't much of an agricultural surplus so the advantages of being a wealthy land owner or lord were so pronounced that they might mean the difference between eating or not eating. Thus the pull of wealth was far more pronounced.

Oerdin during most that time agriculture isnt a factor. Agriculture doesnt really spread out from the Mideast into north central europe till what, after 4000 BCE or so, IIUC. And to scandinavia, not till later.

[lord of the mark]

Originally posted by Oerdin
LotM, yes the phenotype would still exist but would rarely be manifested. The question is how do we explain locations were the recessive trait is the dominate trait? Is it just founder effect? If so then how did the initial mutation spread? Assuming the blue or green eye mutation started with just one person.

how rarely its manifested is going to depend on its frequency. Recessive doesnt mean rare, at least not by definition (O type blood, for example, is recessive, but is the most common type).

So if you have a populatio where "blue genes" are 80% of the genes, it wouldnt be odd to find 50% or so of the population having the phenotype.

You seem to be assuming that all those dark eyed Irish have two dark eye genes, and somehow the blue genes got artificially concentrated, rather than that the dark eyed Irish are all "blue gene" carriers.

As for why blue genes would be that widespread in some localities, yes, it would be either something random, or some evolutionary advantage.

Also, Im not sure if there would be only one mutation. Im not a geneticist, but from what I understand many common traits can in fact result from different mutations - of course then if SEVERAL of the mutations are concentrated in a population, one might suggest evolutionary advantage rather than drift - depending on how many mutations for the trait occured though. From what I understand this stuff gets very mathematical, and technical in other ways.

[lord of the mark]

(This post had poor genes, and failed to survive)

[LordShiva]

I saw lotm's Belgian flag and avatar and for a moment though Colon was back.

Colon