Are human beings diverging in size?
 

I was thinking about this the other day. I think I've mentioned it before, but I'm alone and bored.

We have a social construct where women don't typically date guys who are shorter than them, and men don't typically date women who are taller than them. While a tall man may date women of any size, he's more likely to end up with taller women because there's less competition. A short man is typically going to be fishing almost exclusively off the petite end of the spectrum.

I'm not saying that it'll happen overnight, and there are a lot of confounding factors, but in the ultra-long term, you have a disproportionate number of pairings of tall genes and a disproportionate number of pairings of short genes. So that would logically mean that we're going to flatten the bell curve of heights over time with more tall people and more short people than we would get with random pairings. Right?

Then I wonder about maximum and minimum heights. Do humans have natural limits? With this socially selective breeding, can we keep hitting new maximum and minimum heights? In the dog world, mastiffs and Newfoundlands are probably six times bigger than generic domesticated dogs, and chihuahuas are 20 percent of the size of generic domesticated dogs. Can humans push the same limits and hit mature weights of 40 to 900 pounds? Can we go further? In a thousand millennia, if you're 14 inches tall, you're probably still looking for that 12 or 13 inch wife. And the process would accelerate because she's unlikely to date and marry the 9-foot, 900 pound subspecies of human. What's the upper and lower limit over the course of 100,000 years?

And did cro-magnons and ancient Egyptians have the same social preference? How much of a head start do we have? I'm thinking it's a new phenomenon because a lot of marriages in past times were arranged.

Interesting...

Go to sleep.

Yes.

This has all sorts of implications.

Human height has been given as an example of bimodality for a while, using the average of males for 1 curve and females for another. They used it in my intro to stats course. More recent actual research has been done to prove otherwise. If separating between sexes is not enough to give bimodality then I doubt that natural selection would be enough to create bimodality in the individual sex.

The issue is that breeding tends to average the heights of parents rather than produce extremes, and far more people exist to start with in the average range. Somehow the average height people would need to stop reproducing for this to happen.

As for extremes in height, why would the average offspring be shorter or taller on average than the parents? This occurred through forced selection in dogs.

One thing is evident, Being tall (6'4+) and getting old sucks!

People seem to think that being tall is all fun and games, when in reality it's a pain in the ass. It's hard to find clothes that fit right, and you bump your head into more things than short people do. Plus short people are always asking you to get to stuff that they can't reach. Go find a step stool for crissakes.

I wonder about this a lot.

In modern times the wealthy aren't just intelligent white Europeans - you have the highly educated that come from old money and athletes/actors/musicians.

No one will argue that $$$ = opportunity.

So athletes and actors (considered physically superior or more attractive) now have the earning ability of old money.

I wonder more if Intelligent+Athletec/Attractive become the morlocks and the less advantaged/attractive/athletic become the eloi.

Kind of a reverse of Wells original concept...

I chose the "I think social bias influences pairings, but there are too many confounding factors to make a difference in the long term" option.

Part of me does believe that divergence is inevitable, considering mate selection seems to indicate that humans naturally do gravitate in the manner in which you described. However, everything in our society is so freaking "trend-happy" to the point where I believe there could potentially be some confounding factors that would sabotage the divergence.

That's actually a helluva' good point.

The first thing to do is to not compare us to dogs. Humans have been selectively breeding dogs for 10,000 years, and they can litters of puppies after only about 2. They're waaaaaay farther down the evolutionary divergence path than we probably ever will be.

As for us, I don't think height preference in mate selection will be nearly as much of a determinant as increased mixing of ethnicities, and especially increased health care. If you're like me, all of your friends' kids are considerably taller than you and your friends were at that age.

Nutrition.

This is less true now than a generation ago and continually less true with each future generation.

Modern human evolution more and more favors mental over physical traits (intelligence over physicality) which means all things related to masculinity (muscularity, aggressiveness, etc.) will (and already are) decreasing in the population over time. You already see this in play today. young women today favor skinny girly looking men moreso now than they did a generation or 2 ago and the average male has a ~30% lower testosterone level than a generation ago.

Eventually you can expect a scrawnier and smaller general population, as there will be no need for muscle & masculinity in modern society. Traits related to maleness really do nothing but cause problems and eventually those problems will be weeded out thru science (gene therapy) and natural selection.

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