This answer comes from Michael J. Dougherty, assistant director and senior staff biologist at Biological Sciences Curriculum Study in Colorado Springs, Col.
 Image: SportsLine USA, Inc. TALLER THAN SHAQ?
Humans increased in stature dramatically during the last 150 years, but we have now likely reached the upper limit. The
average height of a human man will probably never exceed that of basketball player Shaquille O'Neal, who stands 7 feet and
1 inch tall. |
Anyone who has ever visited a home built around the time of the Revolutionary War along the back alleys of Philadelphia or Boston has been struck, metaphorically if not literally, by the characteristically low ceilings and small door frames. Even houses built in the early 1800s can make a person of average height by today's standards wonder how the orignal occupants managed to stay conscious long enough to participate in an industrial revolution and a civil war.
For most people, contemporary buildings do not prompt similar claustrophobic concerns. The reason for this difference, as many people have correctly guessed, is that modern humans are taller than those from the eighteenth and nineteenth centuries. In fact, over the last 150 years the average height of people in industrialized nations has increased approximately 10 centimeters (about four inches).
Why this relatively sudden growth? Are we evolving to greater heights, vertically speaking? Before answering these questions, we need to remember that evolution requires two things: variation in physical and/or behavioral traits among the individuals in a population; and a way of selecting some of those traits as adaptations, or advantages to reproduction.
For example, finches that have large, powerful beaks also have an advantage cracking large, tough seeds during periods when small, soft seeds are scarce. As a consequence, large-beaked birds are more likely to eat better, survive longer and reproduce than small-beaked birds. Because beak shape is an inherited trait (one that is substantially influenced by genes), more successful reproduction by large beaked birds means that the genes predisposing finches to large beaks are transmitted to the next generation in relatively larger numbers than those genes encoding small beaks. Thus, the population of finches in the next generation will tend to have larger beaks than finches in their parent's generation.
Let's use this basic operating principle of evolution to predict, retrospectively, the direction of change in human height if evolution were the cause of the change. We know from studies conducted in industrial England that children born into lower socioeconomic classes were shorter, on average, than children born into wealthy families. We also know that poorer families had larger numbers of children.
Given those initial conditions, what would evolution predict? The average population should have become shorter because the shorter individuals in the population were, from an evolutionary fitness perspective, more successful in passing on their genes. But this did not happen. Instead, all segments of the population--rich and poor, from small and large families--increased in height. Thus, natural selection, the process whereby differences in reproductive success account for changes in the traits of a population, does not explain why we are taller.
If evolution doesn't explain height increases, what does? Most geneticists believe that the improvement in childhood nutrition has been the most important factor in allowing humans to increase so dramatically in stature. The evidence for this argument is threefold:
First, the observed increase in height has not been continuous since the dawn of man; it began sometime around the middle of the nineteenth century. In fact, examinations of skeletons show no significant differences in height from the stone age through the early 1800s. Also, during World Wars I and II, when hunger was a frequent companion of the German civilian population, the heights of the children actually declined. They only recovered during the post-war years.
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8 Comments
Add CommentRich = better nourished = taller = predjudice towards taller people. If women from all socioeconomic backgrounds prefer taller mates, then all other things being equal the species actually will become taller genetically. A bizzare case of phenotype causing a change in genotype.
Reply | Report Abuse | Link to thisThe issue with that theory is that, according to this article at least, the genes of those who are taller because of better nutrition are no different from the genes of those with poor nutrition and shorter stature. There should be no change in the genetics of their children, which is why height increase is beginning to level off.
Reply | Report Abuse | Link to thisAh, the great feeling of being right! I received an eyeroll and a scoff from my wife when suggesting that nutrition was a determining factor in height at dinner tonight. She said "You think I'm short because my parents didn't feed me properly?" I hadn't meant it as a personal attack, but now I feel like I can hold me head a little higher :)
Reply | Report Abuse | Link to thisThis explains it for me, have researched a lot in this area
Reply | Report Abuse | Link to thishttp://www.angelfire.com/space2/noah/
I think this is so interesting. We are a mixed family. I grew up in a very large household, and I topped out at 5'4". My mother was a naturalist (nice way of saying hippie.) We didn't eat meat if it wasn't raised on our own land, and we our own eggs. Our milk we often traded our grown vegetable with dairy farmers nearby. I have three brothers that are very tall, and two that are my height (or a little taller). All of my sisters with the exception of one are considered to be short. Considering that we all grew up eating the same things, it isn't nutrition. It is also a very interesting preconception that taller people are healthier. My mother is 5'1", is 83 years old, never goes to the doctor and still goes horseback riding (no joke). She still has the same lifestyle as when we were growing up. My sister works in a convalescent home and she tells me that rarely are any of her charges that are above 5'6" and over 75 years old very active or physically healthy compared with those that are of smaller stature. (Of course this is only one home with about 200 residents, and not a scientifically controlled observation). However, my father was 6'2" and was also very active. Sadly he passed away at the age of 65 of a heart attack. (These are only personal experiences mind you.) This is what spawned my interest because I've noticed that most of the taller people on my fathers and mothers side of the family tended to have shorter healthy lifespans.
Reply | Report Abuse | Link to thisIt sounds strange, but rarely have I seen any very tall people who are also very old?
Height Prediction Calculator for Children
Reply | Report Abuse | Link to thishttp://www.etoolsage.com/calculator/Height_Prediction_Calculator.asp?toolsort=1500
People shrink with age. You can lose several inches by the time you are elderly. Older people tend to be a bit hunched also, which will make them look shorter. I see few with good posture who stand fully upright.
Reply | Report Abuse | Link to thisPlus, older people are from older generations...the peak in tall people are not the elderly people now. I suspect it's the boomer generation that was tallest....studies I've seen show the US peak in height around 1960 (people born in that year). Those people would only be in their early 50s now, not in nursing homes....
Okay nutrition might have a factor but what about those in 3rd world countries who are taller than some who have had a healthy upbringing in the States?
Reply | Report Abuse | Link to thisI think height's solely based on genes. And since most prefer a taller mate the height averages have been slowly increasing over centuries. I heard back when Napoleon was Emperor the average height for a male was 5'6. Now it's about 5'9-5'10. Once your daughters start getting taller and aim for taller mates obviously there is going to be an increase in the overall height, it just takes time. I'm sure one day 6'0 will be average height for males.