Everytime I visit an American historic site like Monticello or Independence Hall, I notice that the doorframes are significantly shorter than they are today. Although I don’t have the figures it seems that, on average, humans have become taller over time – at least a few inches on average over the past couple of centuries.
If we extrapolated height over time, I guess it would follow that humans will continually become taller and evolve in other ways, but I don’t understand WHY this would happen. It’s not like our environment necessitates our bodies adapt in search of food or safety – which is, in essence, why animals evolve anyway. What are the physical limitations of our own evolution? If, over the past thousands of years, we have become taller/lankier and even less hairy, what will the human race look like in the year 2200? 2500?
People are getting taller mainly as a result of better nutrition, healthy living conditions, and better pre-natal health care. Take a look at Japan after WW II, and how the average height has increased with a better food supply.
There’s no reason to believe that this will continue at this pace. We may have reached our height limitations already, based on environmental factors.
While I can’t cite a source, I seem to recall some news story pointing out that the extremely tall die younger. This isn’t just from accidents in a world built for smaller people, though the taller you are the more it hurts to fall (witness babies)
The human heart also isn’t good at pumping blood around a 7-foot body. Witness Wilt Chamberlain’s early death if you’re looking for an anecdote.
Point: there’s no reason to assume that evolution would select from a height much greater than contemporary human standard.
I can’t help thinking, though, that through his 20,000 sexual encounters, Wilt may have turned out to be QUITE fit from the evolutionary standpoint, at least in terms of passing on his genes.
I’m not sure I totally agree with you, Telemark. I think there isn’t any reason to believe we WON’T continue to increase in height. Yes, our nutrition, pre-natal care, etc. are all better than they have been in the past – but isn’t it fair to assume that those factors, including living conditions, will be better in the future than they are now?
As Telemark said, one of the big reasons humans, on the whole, are taller now is due to nutrition.
A few anthropologists (Morris, Diamond, et. al) have proposed that there MAY be a cultural evolutionary process in play. That is, (they posit) that since tallness is seen as related to health, humans may have an instinct (or have developed an instinct) to prefer mating with taller folk, thus culturally evolving taller offspring. Not that humans can’t and don’t override lots of mildly hardwired instincts, but over time this may make a difference.
Another thing that may be throwing you off is the height of our forebears. They were shorter, to be sure, but not much shorter. There is a tendency to fall for the optical illusion created by doorway heights and room sizes. In general, the comparatively voluminous room sizes we’re used to today are made possible by efficient building materials and techniques and particularly by efficiency of heating. In the not so distant past, rooms were kept small, doorways short, and hallways narrow for ease of heating by fireplace alone. The exceptions were the grand dwellings of the wealthy, who could presumably just toss money onto the fire to keep the palace warm. Of course, even a castle, with a huge Great Hall had teeny little bedrooms because of the heating thing.
Even after things like rooms, beds, doorways, chairs, etc. could be made larger and still be efficient (by the introduction of new technologies in heating for example), traditions kept rapid change from sweeping away the old-style little-bitty things.
You mention Monticello…IIRC, Thomas Jefferson was 6’4”. Did you see the little bed he slept in?
Evolution is not a predictor of increases in height. People might well evolve to a smaller size, if there were a benefit.
What is known from the historical record is that height has varied through time. Robert Lacey and Danny Danziger wrote a book called “The Year 1000 – What Life Was Like at the Turn of the First Millenium” and in it they say:
“If you were to meet an Englishman in the year 1000, the first thing that would strike you would be how tall he was–very much the size of anyone alive today.” The Anglo-Saxons were not only tall, but also generally well fed and healthy, more so than many Britons only a few generations ago.
The authors attribute the healthier diet to more fruits and vegetables; low-fat meats (all animals were free-range animals and not penned); and the absence of sugar in the diet.
We’ll look, excepting cosmetic changes and presuming we don’t do ourselves in pretty much the same. Several hundred years is much, much too short a time for evolution all things being equal. Now, in 22200 we might see something interesting (although that’s still quite a short time period) but will we last another ten thousand years let alone twenty?
What Collounsbury said. You mentioned Monticello, etc, from just a few hundred years ago. That is nowhere near enough time for evolution to have a noticeable effect. Any changes are due to cultural changes, like nutrition, as has been mentioned.
I think I unintentionally limited the scope of my question. I understand the reasons why we HAVE gotten taller, at least slightly, but I don’t see any reason to believe humans could look radically different over time. Granted, a few centuries is not nearly enough time to notice significant changes, but if you compare our ancestors from 10,000 years ago or more to today and extrapolate, well . . .there simply isn’t any reason to believe we’ll stay the same as a race.
Take other qualities besides height. Judging by my grotesque feet, it appears that my pinky toe is a mere stub with little purpose. Is it crazy to think our little toe will someday evolve into nothing? It could be argued that the opposite, an increase in length, will happen to our fingers.
I have to believe that our bodies are continually evolving in other ways as well. There is an unknown threshold for these apaptations – the point at which height causes heart failure is a good example. Thanks.
10 K years ago we looked just like we do now – well except for our fashion sense and the like. You have to go back more like 70K to get real differences and more likely 100K.
Well, is there anything selecting for its disappearance or making other toes bigger? Maybe there is, but remember we have to have it work for a real damn long time.
Evolution typically happens slowly. Very slowly unless some terrible (in the sense of severe) pressures are applied to a population for a significant period – e.g. homo sapiens appears to have emerged out of a constriction event --something which knocked the relevant population’s numbers down to the low hundreds or so and held it there for hmm, I am thinking 30K years, might be off on that. Who knows what it was… In any event, we should not expect anything whacky to happen to our race in the future – the time frame for real changes is so long I for one doubt we’ll last that long.
Given that successful people on the average have higher IQ scores than non-successful people due to better formal schooling and superior home teaching from their high IQ (successful) parents, does that mean that civilization as a whole is getting dumber because the least successful class of our society tends to have the most kids?
Well, there’s a biological component to intelligence as well. Evolution and natural selection are closely intertwined aren’t they?
Say you have a population that consists of two groups of people: Smart People and Less Fortunates.
500 Smart People who each have 1.2 kids
1500 Less Fortunates who each have 2.8 kids
Barring interbreeding between the two groups, microwave accidents, asteroids, Jerry Springer and all other relevant factors, after 10 generations we have:
3,096 Smart People
44,429,515 Less Fortunates
Originally, Smart People numbered in at 1 for every 3 less fortunates, after 10 generations, there’s only 1 smart person for every 11,000 Less Fortunates.
Of course in RL a few extra factors apply like interbreeding and Maury but the underlying model remains the same.
Natural selection is the mechanism of evolution, but the relevance is what?
Intelligence
I do not see any reason to presume that (1) intelligence varies so wildly by population (2) that historically ‘smart people’ have had less children than dumb people (3) that our cultural judgements of smart and dumb have any necessary relationship with actual underlying genetic capacity. (4) your model makes the erroneous presumption that there is no interbreeding between the populations and it ignores the phenomena of regression to the mean.