So tall we will fall/

[Dean Mullen]

Some studies & common sense can tell that every generation is getting slightly taller due to improving lifestyles over time. But what worries me about this quick almost man-made evolution is that if we get really tall really quick could there be consequences? based on the science that as you increase a volume, its weight increases more than its strength, what if humans increase volume over time so quickly that our weight is too much for our strength to overcome and people essentially become weaker and weaker? the science of increasing volume states that humans are getting weaker every generation.

 

Although no significant evidence suggests this, I theorize its happening so slowly that we don't notice it. But since the rate of our civilizations advancement in technology hence lifestyle is increasing its rate of increasing lifestyle itself does this suggest that humans will become very weak and when born perhaps collapse under their own weight within a few hundred years?

[SMF]

I don't recall any science that says that every generation is getting taller. In fact, what I remember is that height has only increased as nutrition improved late in the 1800s and stopped increasing in the US, for example, after WWII. Weight is increasing as the result of changes in diet and exercise habits and this is already causing many problems with hip and knee joints and also the increase in type 2 diabetes. Although you didn't specify what you mean by "man-made evolution" it is clear that these changes can not be explained by evolutionary theory. For this latter point see this short Scientific American piece- http://www.scientificamerican.com/article.cfm?id=why-are-we-getting-taller SM

[PhDwannabe]

Although no significant evidence suggests this, I theorize its happening so slowly that we don't notice it.

Dean, I commend your intellectual curiosity. But for crap's sakes, take a deep breath before you type something like this. A person may as well say, "there's no evidence for unicorns in the room, but I theorize that they're simply standing very, very still."

 

based on the science that as you increase a volume, its weight increases more than its strength

What on earth does this mean? Suppose I have a sphere of radius 3 units, which makes its volume ~113 units³. And then I increase that radius to 4, making its volume ~268. Fascinating. What, exactly, is the "weight" of this sphere? What exactly is its "strength?"

 

Some studies & common sense can tell that every generation is getting slightly taller due to improving lifestyles over time

What studies? Point them out. And why on earth would common sense tell us this? This is precisely the sort of thing common sense wouldn't tell a person, for exactly the same reasons you yourself point out: it's happening so slowly. It isn't any more apparent to "common sense" than climate change or continental drift. If you'd bothered to actually read about it for ten minutes, you'd quickly find out a couple of general things. Namely:

 

There is a persistent, near-mythical belief in the steady increase in height throughout history which is not supported by evidence. Ancient and pre-modern people were taller than we often tend to estimate. Yes, there have been significant jumps since the dawn of industrialized food production and public hygiene. But there have also been ups and downs as economies (and hence, diets and behavior) changed. For instance, average height in Europe fell a bit as the Roman Empire declined, as the economy simplified, peoples' diets became less varied, and basic public health facilities (think aqueducts and toilets) decayed. You raise kids 1) on diets of largely one or two staple carbohydrates, 2) under conditions where they have to spend a lot of energy working, and 3) with a load of pathogens and parasites that they have to essentially "donate" a lot of their calories to, they grow shorter. Change those things in the other direction, they get taller, and puberty hits earlier. It's not that complicated. You really don't even need evolution to explain most of it. I swear, look around for ten minutes, and you can find all of this.

 

Or, go find the data that support the idea that we're evolving towards some point where we'll all fall over, and present them.

[Cap'n Refsmmat]

What on earth does this mean? Suppose I have a sphere of radius 3 units, which makes its volume ~113 units³. And then I increase that radius to 4, making its volume ~268. Fascinating. What, exactly, is the "weight" of this sphere? What exactly is its "strength?"

If I were to simply take a human and make him proportionally ten times taller and wider and so on, his weight would go up as the cube of its size but his bone strength as its square, meaning the bones would be proportionally weaker and he'd be more vulnerable to fractures.

 

Something like that. I might've gotten the powers wrong.

[John Cuthber]

All that shows is that mice will not be constructed in the same way as elephants.

So what?

 

Evolution isn't stupid.

If there's some reason why tall people have more children then the race will, on average, become taller. However if these tall people can't do a lot because their backs are not strong enough then they won't have so may kids and the average height will fall. Actually it will just never get to the point where being tall is a significant problem.

 

So the answer to te question "does this suggest that humans will become very weak and when born perhaps collapse under their own weight within a few hundred years? " is no.

[Marat]

Evolutionary processes interacted with changing weapons technology initially to make people taller, since ergonomically you can fight more effectively with your bare hands if you are shorter and more stable on the ground, while you can fight more effectively with swords, shields, and spears if you are taller. Progress in height after that occurred mainly through improved nutrition, hygiene, reduction of devastating childhood diseases, and overcoming of rickets in children of the early industrial age who lived in city shadows so much they were deprived of sunlight.

 

However, studies among Harvard University undergraduates, who had already experienced most of the benefits of improved nutrition, hygiene, and reduced childhood diseases by the 1920s, showed that their average height peaked some time ago. There evidently is a maximum, optimal height above which improved conditions will not induce humans to grow.

 

Generally, people overestimate the extent to which human height has increased over historical time, in part because doorways in earlier centuries used to be constructed as narrow passageways through which people were expected to go in a stooping posture, so that people visiting old castles assume that those who first occupied them were actually as short as the doorways were. Also, historical uniforms in museums shrink, again making it seem as though people used to be much shorter and smaller than they are today.

 

An interesting correction to this impression is offered by the data collected by the Union Army on recruits in the American Civil War, when the average man in service was found to be 5'8" tall. Today the average male height in North America is 5'10" tall, which is not all that different. Historical suits of armor which of course do not shrink in size also demonstrate that normal height, at least among the upper classes able to afford suits of armor, in medieval times was not as short as people expect.

[Cap'n Refsmmat]

Evolution isn't stupid.

If there's some reason why tall people have more children then the race will, on average, become taller. However if these tall people can't do a lot because their backs are not strong enough then they won't have so may kids and the average height will fall. Actually it will just never get to the point where being tall is a significant problem.

Unless, for some strange reason, women find men in back braces to be incredibly sexy.

[PhDwannabe]

Evolutionary processes interacted with changing weapons technology initially to make people taller, since ergonomically you can fight more effectively with your bare hands if you are shorter and more stable on the ground, while you can fight more effectively with swords, shields, and spears if you are taller.

 

Sounds like quite the just-so story to me. Aware of any evidence for it?

[John Cuthber]

Interestingly, this

"Evolutionary processes interacted with changing weapons technology initially to make people taller, since ergonomically you can fight more effectively with your bare hands if you are shorter and more stable on the ground" is reasonably testable.

Are Sumo wrestlers generally taller or shorter than the population from which they are chosen?

 

My hunch, based entirely on prejudice, is that the wrestlers are tall and so the idea is false.

[Marat]

Since Sumo wrestlers perform in a type of highly ritualized combat with its own peculiar rules, I don't think any generalizations about the anthropological significance of the ergonomics of combat can be drawn from their example.

[John Cuthber]

Since Sumo wrestlers perform in a type of highly ritualized combat with its own peculiar rules, I don't think any generalizations about the anthropological significance of the ergonomics of combat can be drawn from their example.

I do.

However, perhaps you would like to come up with a better test.

Alternatively you might want to accept that your assertion, being untestable, is probably unscientific and shouldn't be here.

[SMF]

Perhaps male stature has more to do with the tall guys, who don't go to war, but stay home and are selected by the ladies.

 

http://www.antropo.uni.wroc.pl/wp-content/uploads/2009/05/PAWLOWSKI_ET_AL_NATURE_2000-1.pdf

http://rspb.royalsocietypublishing.org/content/270/1516/709.full.pdf

http://dfred.bol.ucla.edu/SalskaFrederickEtAl-2008-PAID-ConditionalMatePreferencesHeight.pdf

 

SM

[Marat]

Read any anthropology textbook from an Anthropology 101 course. The theory of the relationship between weapon development and human stature is standard knowledge in the field, not some private theory of mine.

[PhDwannabe]

Read any anthropology textbook from an Anthropology 101 course. The theory of the relationship between weapon development and human stature is standard knowledge in the field, not some private theory of mine.

I took a couple of anthro courses in undergrad not too long ago, of course including intro. I just also asked two friends--an anthro major and anthro minor. None of the three of us has ever heard of such a thing. I'm not outright rejecting what you're positing here, Marat, but you may have to do a little better than that.

[SMF]

Marat, I don't necessarily disbelieve your assertion, you just haven't provided any evidence. I posted what I could find quickly that was not behind a paywall. I am skeptical of the weapons/stature idea (lacking any scientific evidence) because, although violent confrontations provide fairly strong selection pressure for the combatants it is diluted by other factors, not the least being promotion of survival of those who cooperate with their fellows best in a desperate situation. Also, very many more men die from other causes between short periods of conflict and there is a disproportionately large number of men who don't die in battle because they avoided the conflict. SM

[Phi for All]

Read any anthropology textbook from an Anthropology 101 course. The theory of the relationship between weapon development and human stature is standard knowledge in the field, not some private theory of mine.

The only abstract I could find quickly seemed to run counter to your claim.

 

Trends for reduced (emphasis added) limb size and stature seem to be correlated with improvements in the types of weapons utilized and a shift from aggressive to more docile game.

 

An interesting correction to this impression is offered by the data collected by the Union Army on recruits in the American Civil War, when the average man in service was found to be 5'8" tall. Today the average male height in North America is 5'10" tall, which is not all that different.

While the sample is skewed because one is for military men and the other seems to be for men in general, I wouldn't say that an increase of 2" in 150 years is "not all that different", not in terms of evolutionary scale.

 

Imo, there is too much ad hoc justification in this thread for it to be in Medical Science. Can we thicken the ice upon which we tread with a bit more rigor?