[Update Edit 12/25/ 2012: I forgot to consider the fact there there is another type of size range restriction/breakthrough that does exist, and that is the phenomena of island dwarfism/gigantism aka insular gigantism/ dwarfism. We find mini-elephants, mini-humans, giant birds, giant rodents, giant ducks, giant tortoises and lizards, etc. in these situations. However, we realize that for this case, like the other cases, it was geography that was the real cause for the genetic evolution which chose to go either towards the super-sized or the mini-sized version of normal sized fauna. Again, we see that groups of people may not have genetic propensity towards certain size ranges, but that it is something else that causes the group to over time evolve and adapt their bodies towards that geography and climate.]

Here is another commonly accepted height idea and/or misconception which I wanted to resolve once and for all. I see this so often on the internet forums and boards like Yahoo Answers and Answers.com where a the original poster raises the question about whether they can still grow through exercises and supplement pills. They are interested in seeing if there are any solutions or options in making themselves taller. Almost always the final answer comes from a poster who answers with a statement that goes along the lines of the message

“You will grow only to your predetermined height which your genetics have set for you…. Where you are in height was where you were always supposed to be, and it was already laid out as your fate towards height from the moment of conception and your genome was set.”

This type of message is enough to stop any other people who wanted to make their own opinions heard. Anything that comes after the “genetics determine height” message gets ignored since it does seem that there is nothing one can do to go beyond the height that is supposed to be completely hereditarily based.

However, I think the point to note about these types of people is that their thinking is slightly inaccurate. Sure, a significant part of one’e height is determined by genetics. I wrote in a previous post entitled “How much of human height is genetic and how much is due to nutrition?” where a researcher showed that a significant percentage of one’e height is determined by about 60-80% by genees. What the people forget is that the height they are talking about is not a set point which can not be deviated from.

The best example is to deviate in the wrong direction, to become shorter than what “genetics determine height” state. The best example is in the major height difference between the two nations of North Korea and South Korea. In terms of ethnicity, they are exactly the same. The two nations have only been geopolitically separated from each other by 60 years and the ethnic makeup of the two countries show that their is almost no foreigners to dilute the height average of the two nations. From certain sources (source 1, source 2, source 3), we find that the average height of South Korean males to be around 5′ 9″ and the average height of North Korean men to be around 4-8 cm shorter. Some sources say the actual height difference is 3 inches and others say it is 2 inches.

For the average person, 2 inches may not seem that big of a change, but when we consider the fact that only 60 years can cause this type of height variation between two groups of people who are exactly the same, we see that one’s nutrition and food quantity and lifestyle is a huge determinant of one’s height.

The main point is that when the people say that one’s genetic’s determine height, what they are actually implying is that one’s maximum full height is determined by one’s genetics. What they never state is that the genetics won’t help keep a person to become shorter than what their genetics have set for them. In the most extreme case, I could point to the case of Yao Ming. Born from a 6′ 7″ father and 6′ 2″ mother, we could say that Yao Ming was destined to be tall. From a statistical and genetic point of view, we could say that he would probably eating the same kind f food and getting the same type of nutrition as his fellow man in his country of origin end up on the taller distribution side of a height spectrum. However, it would still not be hard from a lifestyle and nutrition point of view to actually limit even his height to become less than the mean height. I know a few cases where male offspring of two people over 6 feet  tall end up being around the 5′ 8″ height range.

Another coount I could make to show that the genetics determine height arguement is inaccurate is over the height increase we see from the Dutch ethnicity of the last 150 years. Around the end of the 19th century, we note that the average height of the Dutch was among the shortest of all the European countries with a male average height of around 5′ 4″ -5′ 5″ (source ). 1 in 4 males could not enlist in the army because they were below the height cut-off point of 5′ 2″. If two well traveled people were to talk about the stature of the Dutch as an ethnic group, they could have easily argued that the Dutch are just “predisposed to be on short due to genetics” but of course 150 years later we find that the Dutch have shot up by almost 1 entire feet (12 inches) in height to around the 6′ 2″ – 6′ 3″ mark. This may be one of the most dramatic changes in height for a group of people we have ever. And we have not even considered the fact that the average height of the people in the Netherlands have been statistically pushed down from average and integrating the smaller height of inmigrnats which have been coming to the country for the last 100 years. The Netherlands have been traditionally for the longest time quite possibly the most liberal, tolerant, and multicultural country in the world. 1 in four people from the Capital, Holland is made of immigrants. If we truncated those height, we might realize that the real average height of native Dutch people is probably around the 6′ 3- 6′ 4″ range for males.

One point that can disprove the idea of genetics determining the upper bound level of possible height, is that the children of these immigrants to the Netherlands have almost all grown taller than their parents or grandparents, sometimes even shooting up over having a 1 feet in difference. Of course the idea of 1 feet of height difference between 1 generation is on the extreme side but it does happen a lot for the people who decide to move from their native country to another country with better living conditions and better healthcare. The researcher who goes only with the idea of “genetics determine one’s height” would not understand why kids of short groups of people who are from short countries who are supposed to be hereditarily & idiopathically short would grow to be so much taller than the genetics had determined them to be.

In addition, the arguement can be further disproved with what we are seeing in the height increase of children in India and China over the last 20 years. I showed that the children have increased in height by around 2-3 inches for both India and China in previous posts. While cultural anthropologists could have stated using superficial genetics to argue that the Asians are short 20 years ago, they may have to change that idea in another 20-30 years time when the living conditions of many of the “traditional short” Asian countries improve and the people increase in height along with it.

In terms of correlation, we see from classical nutrition books like “The China Study” that the people of rural China from 20 years ago had less instances of Cancer and Heart or Cardiovascular Disease and that is because they were living off of a vegetable, plant, bean, and tofu based diet with very little meat . They lived longer, just like how the Japanese and Okiwanan’s lived on seafood, tofu, vegetables, and little red meat like cow. Both these groups of people had extraordinarily low levels of Cancer and Heart problems. However we must remember that there is a clear positive correlation between increased height and increased cancer risks. We see that while the Chinese and Japanese have been living on plant based diets and live longer, they are also shorter. The newer generations which are richer who have access to red meat and more protein besides just beans and tofu end up taller  but also have higher risk for cancers.

At this point I am going to make general trends which show how the correlations are supposed to go together …

1. Increased Height correlates to Increased Intelligence correlates to Increased Cancer Risk and Decrease In Life Expectancy.
2. Decreased Height correlates to Decreased Intelligence correlates to Decreased Cancer Risk and Increase In Life Expectancy.

Sure, there is no doubt that in the asian countries the people are still on average shorter than their native European counterparts, but if we really think of height in an evolutionary point of view, we can see that there is no valid evolutionary reason for people of different countries to be of different height. The only idea that can back up the idea that certain people of certain ethnicities (thus different genes) are held to determined maximum height potential is over the Anthropomorphic Principle Bergmann’s Rule which I had written before in an old post entitled “Bergmann’s Rule, Appplication On The Human Species“. To refresh the memory of the reader, Bergmann’s Rule states the idea that in general people who are from ethnic groups who are traditionally from countries closer to the equator of Earth will be shorter than people who orginated from nations further away from the equator. Of course this rule means that one’s geography is the main reason for one’s height. Thus it implies this causality.

Geography –> Influences Genetics –> Evolution results and body gets adapted –> Increased/ Decreased stature.

Besides, this idea, the other idea is that the laws of physics, specifically the force of the gravitational force exerted on each cell’s surface puts a limit to the the maximum potential height any human can reach. I wrote about this idea in another old post entitled “What Is The Highest Theoretical Height Of The Human Species?“.

So there is two factors that can determine human height, one is from physics (gravitational force) and the other geography, which is also indirectly physics based. From a completely objective point of view, it doesn’t make any evolutionary sense for people to have a genetic maximum for their height. We saw in past eras like the Jurassic and Cenozoic period that reptiles can grow to insane sizes. The fact that we stand on two limbs, and not four limbs which would distribute weight load out like the largest land animals, the long necked dinosaur sauropods, should still not restrict our maximum height since the two legged Tyrannosaurus was over 20 feet tall. The physicists have proven  from using elementary physics principles that an insect with a exoskeleton shell can not be over a certain size (unlike crazy science fiction movies like Godilla Vs. Mothra) because the weight of the hollow shell would crush them. The physicists however show that there is no limit to how tall bipedal mammals can become, as long as the cartilage or non-bone connective tissue  of the leg joints is strong enough to hold up the weight above it.

In conclusion, it  shows that the height of a person with tall parents and relatives can not be guaranteed to be tall due to the factors of malnutrition, pathologies, and even psychological stress. It also shows that the height of a person of short parents and relatives can not be held below a certain height level due to better lifestyles and nutrition. The genetics argument is not accurate and only valid in certain parts.