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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Small in size and tall in stature.

Their offspring may break the space time continuum

http://i.dailymail.co.uk/i/pix/2012/...13_468x762.jpg

This would not affect gene or allele frequencies. So I don't think there would be any noticeable differences short or long term.

Got a link for this, playa?

the main point I got from the post is that you are bored and you took the time to share that with us:D

I can't find the specific one I read a while back, but here are some similar findings:

http://heartiste.wordpress.com/2013/...terone-levels/

http://www.ncbi.nlm.nih.gov/pubmed/17062768

My Wife is tall. She's constantly bitching about wanting to be short.

tldr

I am sure there is a study linking height over time.

Lincoln, in his time was a giant at 6'4". Then he added to it with the Stove Pipe hat. I believe Washington was 6'1". The median was ~5'4"?

I toured castles in Europe and many door/archways were much shorter then you find today. I saw a suit of armor that "Sir Whatchamucallit the Giant" wore and it was for a 6'1" person. What was crazy thou was the size of the swords they wielded. Two handed swords were 6' long. How the heck did these munchkins swing those all day? They must have forearms like Popeye!

My dad's parents were both under 5'7. My dad is 6'4. I am 5'9. My brother is 6'1.

I think it's all about genetics...basically a crapshoot. Every tall family has a short relative, every short family has a tall relative.

My Dad was 5'7 and Mom was 5'3. I'm 6'5 and all my Brothers are over 6'1. It's weird.

There's no correlation. My parents were average height and I'm 6'4". My five siblings are of average height. My HS BB teammates in the front court were taller than me. Their parents were of average height sans one mom. It's hit and miss and not something to lose sleep over.

There's always going to be exceptions. I'm talking about the bigger pattern underneath. I'm no Gregor Mendel, but it seems to me like if tall people continue to marry tall people over the course of a thousand years, their kids are on average going to be tall. And the opposite is true with short people. They're going to pull the distribution out on average.

The height of each sex within a breeding population will always follow a normal distribution. The stronger the height correlation among mating pairs, the more the distribution will broaden. The more people interbreed with people of various heights, the narrower the distribution will become.

Factors that will contribute to maintaining a normal (bell shaped distribution):

When people mate, the mean height of their offspring will be an average of the height characteristics of the two parents. An extremely tall parent will most often be mixing genes with a shorter parent (even if they are taller than average), thus pulling the tall parent toward the middle. For example a parent in the one percentile mixing with someone from the five percentile gives an offspring at the three percentile, on average.

Correlation of height characteristics between mating pairs is <1.

The height of the offspring will be a mixture of the height of the two parents, plus random variation. The random variation tends to smear the effects derived from correlation of mating pairs.

The middle is populated from both sides: offspring from tall people and short people will tend toward the mean, both due to breeding with people closer to the mean and random variation. Extremes can only be populated from one direction. In the above example of a three percentile offspring on average the random variation could propel them to a 0.5%, i.e. taller than either parent.

The breeding population is always greater in the middle than it is at the extremes.

All of the above assumes that the specific genes that contribute to the height characteristics of one parent are the same genes that contribute to the height of the other parent. If different genes are contributing to the height characteristics of the two parents, the offspring could experience synergism where the mean offspring is taller than either of the parents.

Your stating this with the supposition that all shorts breed with shorts. I don't think that's true, similar to how inter-racial marriage exists, so does inter....height marriage? You get the point. Plus there are also so many other biological factors that go into this as well.

this is interesting. there are no "bigguns" in either of my parents families. my dad is 5'9 my mom a little shorter. I am 6' and was the athlete, my brother is 6'2 and could give a crap about sports. pissed me off man! two more inches and I coulda been a contender! ROFL
our height is.....weird.

my kids.......my wife has freaks of nature in her family. she is 6', her dad was 6'4, her two brothers are 6'2. she has uncles and cousins even taller. so I had some "high hopes" (pun intended) for my kids. worked out OK for my daughter. she is 6' and HATES it, yet she was quite the volleyball player. my son is pushing 6'2, not the 6'5 monster I'd hoped for....but he'll do! so my kids are the offspring of two 6 footers and on my wifes side there was hope of super tallness....didn't really happen.

in the end....looking at family history....not a lot of it makes sense in my group.

There is something that I haven't seen mentioned. The amount of hormones we ingest and the affects that has had on our bodies. Not to mention all of the steroid based medicines that are handed out like candy to children.
To me those two things play a pretty large role in the changes we see as well.
You all remember what girls looked like when you were in school. I guarantee you it is not how they look today.

amen to that brutha!
I'd go to my daughters high school volleyball games and you just cannot tell what it is you are looking at.
is that a woman or a student?
is that a coach or a player?