When a mother and father both exhibit genes for short stature, they commonly wonder if their children will also be short. Genetics can often deliver unpredictable combinations that surprise parents and children alike. Further, environment and nutrition play an important role in child development. Can short parents have a tall child?
Yes, short parents regularly do have a tall child. However, there are over 700 genes that play a role, making height difficult to predict. Complete nutrition during development also results in taller children, though not taller than the determining genetic factors.
Some genetic traits are dominant, recurring in each generation. Other genetic expressions become recessive, nearly disappearing in offspring, only to resurface after several generations. As well, the environment and nutrition during development play a key role in the full expression of genetic potential.
Table of Contents
Mid-parental Height Predicts Children Taller Than Parents
In medical practices, the mid-parental height is often used to predict the height of children. This measurement is calculated by averaging the height of both parents, then adding 7 centimeters for males, or subtracting 7 centimeters for females.
This measurement seeks to:
- Predict the height of the child at 18 years old
- Plot height as a percentile chart to track projected growth rate
- Determine the genetic potential for growth in the child
This measurement is relatively reliable if the parents are both of average height. However, when both parents are of dramatically different heights, the mean height measurement loses accuracy as a predictor for child height.
This is because the range of potential heights for the child is much larger. Usually, children attain the average height of their parents within two standard deviations of the mid-parental height. However, when one or both parents are of unusual height, the number of children who fall within the predicted height drops off sharply.
[Standard deviation is common in research statistics. It’s basically the amount of range in your data, or how much you data is dispersed or spread out around the mean (average). Source: Statistics How To]
Regression To The Mean – It’s Genes Not Parental Height
According to Wright CM, and Cheetham TD, when both parents are of unusual height, the children tend to attain heights closer to average.
Mean height is simply the average height of the population. This is the height that the majority of peers will attain, within two percentiles higher or lower than average. Mean height also takes into account the fact that genetic males attain a taller height, and genetic females attain a shorter height.
When both parents are unusually short, there is a higher likelihood that the child will achieve a taller height than both parents. The child will likely still be shorter than average but will display genetic traits that attain closer to an average height than both parents. So yes, the child will likely be taller but not exceptionally taller.
The same height difference is likely to occur with parents who are both unusually tall. While the child may also be taller than most peers, he or she will also likely regress toward the mean and be a little shorter than both parents.
Genetic Outliers Cause Very Tall Kids From Short Parents
While genetics can be largely predicted, it always remains to be seen what genetic traits ultimately appear in the child. Due to the immense number of gene combinations that are available for combination and expression, outcomes are sometimes surprising.
Children below the second height centile: effect of adjustment for regression to the mean on difference between actual height standard deviation score (SDS) and mid-parental SDS.
The table in this study by Wright and Cheetham also clearly shows that while the majority of children will fall within two standard deviation scores of the mid-parental height, there are always outliers that fall way above and way below the mid-parental height.
So, while the parents may both be short, the genes might pair up in a way that causes the child to grow well beyond the height of both parents. This large deviation is not as likely to occur, but it is possible. The most likely deviation is a small one to two SDS above the height of both parents.
While this may not seem like much, within a few generations, this height change can add up to a large difference. This is especially true when children choose mates with a higher genetic potential for a taller height.
After several generations, the average height of family members can be affected.
Personally, I have two short in stature parents, with both under the average height for their sex. However, all three of my brothers are taller than my parents, my dad in particular.
My youngest brother (in fact, the youngest in the family) is not only taller than my petite parents, but he’s also taller than both older brothers, as well as taller than the average male height. With him being 6′ 1′, he is several inches above the average American male, whom the CDC currently ranks at 5 foot 9 inches.
Thus, outliers are possible, especially when other factors are added in such as nutrition, which we’ll address a bit in a later section.
Genes That Affect Height In Tall Children
It is a common misconception that height is determined by either two tall genes or two short genes coming together. In fact, there are over 700 genes that have a small impact on height. Each parent contains these genes in a myriad of combinations. When the genes pair up in offspring, it is highly unpredictable what the pairings will be.
These genes that affect ultimate height include:
- Bone length
- Amount of cartilage
- Genetic diseases that inhibit growth
- Cellular growth patterns
- Collagen metabolism
The human genome is passed down through polygenic inheritance. This means that for every single human trait, each person contains two genes in a unique combination. When these genes pair up in procreation, of the four possible genes, only two pair up for each trait.
Every biology class includes a study of the Punnet Square, which is a visual chart that shows possible genetic combinations for the offspring from two parents. For traits such as skin color, eye color, and hair color, these squares can be relatively simple and accurate.
However, the Punnet Square is not much help when it comes to predicting a child’s height because of the 700+ genes involved in height. Height is not simply a result of dominant or recessive genes pairing to create observable traits. It’s more like a genetic lottery, with the results being only generally predictable.
Genes Account For 80% – Short Parents Have These Genes
While it is easy to blame these over 700 genes for height, that is not a complete picture. These genes account for only about 80% of the outcomes concerning height. The other 20% of factors that affect ultimate height are external.
These factors include:
- Exposure to tobacco smoke and other toxic substances
- Activity levels
- Quality and quantity of nutritious food
- Access to quality healthcare
While there appears to be some correlation between ethnicity and overall height, it has been shown that these differences are largely removed in future generations when families migrate to countries where nutritious food, quality healthcare, and higher-income are available.
Further, children who eat a healthy, balanced diet give cells the vitamins, minerals, fatty acids, and proteins needed to replicate more efficiently and with greater accuracy. This highly nutritive state within the cell creates the best possible environment for healthy genetic expression.
Children who are encouraged to be active in play and sports are shown to grow more quickly to a taller height. This activity encourages nutrient metabolism and cellular growth at a higher rate than sedentary lifestyles.
Specific Dietary Effects On Genetic Height Traits In Kids
Genetic expression does not occur in a cellular vacuum. These cells are vitally dependent on a steady and healthy supply of:
- Fatty Acids
While the transcription and replication of genetic sequences are being carried on continuously within each cell, a deficiency of these nutritive supplies within the cell can have a detrimental impact on genetic expression.
Vitamins such as A and D directly impact gene transcription as it is happening, either positively or negatively determining the outcomes. Other things, such as water-soluble fiber, affect the rate of gene transcription.
Types of fatty acids consumed can determine healthy gene expression or diseased gene expression. For example, trans-fat and saturated fat intake directly affects gene expression for obesity, heart disease, and cancer. (Source: The American Journal of Medicine, Vol 106, Issue 1)
Gene Mutations Can Cause Tall Children From Short Parents
In terms of the 700+ genes responsible for growth rate, these various nutritional factors can have a large impact on the rate and effectiveness of gene transcription for things such as bone length and collagen metabolism. Further, it can impact whether or not a gene mutation occurs during transcription.
While many genes experience damage during normal replication, poor nutrition can make the cells unable to fix the damage. This inability to fix problems occurring during transcription can cause permanent damage to the genome. When this damaged genome is replicated, the result is disease and poor genetic expression.
In simplest terms, the cells are full of building blocks that are obtained through nutrition.
If the cell is being supplied with damaged blocks due to poor nutrition, high chemical content, or toxicity, then the cells built with these blocks will also be damaged.
Further, when these damaged blocks become part of the blueprints used to build new cells, then the body continues building damaged cells with damaged materials. This results in poor health, disease, and less than optimal gene expression. For babies, this blueprint can be damaged in the womb through maternal neglect and toxicity.
Are There Techniques That Can Make Someone Taller?
There are definitely ways to ensure that a child doesn’t fail to reach their determined height set by the genetic factors in their makeup. Malnutrition and sometimes prolonged dieting, anorexia, and starvation can ‘stunt the growth of a child.
Yet, contrary to the claims of some that by willing it so, a person can change the predetermined genetic code within them, someone cannot make themselves grow taller. There are surgeries and other sometimes painful processes that can physically alter a person skeletal system, but these are extreme and could lead to severe problems.
Though there are ways to make certain that a child reaches their full potential height, it takes many generations of dietary and environmental changes to raise the average height of a region of people. It is not something any one of us can do in a single lifetime for ourselves or our culture.
All of our dietary decisions matter for future generations and their potential height.
The Takeaway on Can Short Parents Have A Tall Child?
While parents may assume that their short stature will automatically result in short children, this is not necessarily the case. The overwhelming odds are that the children will outgrow their parents by a few centimeters, at least bringing them more towards average height, particularly if environmental factors work in agreement with good health.
To be clear, there are definite steps that parents can take to ensure that their children have the right environment and nutrition to achieve full and healthy genetic expression. These steps include ensuring that the environment in the womb is healthy and free from toxins. After birth, parents can help the child grow by providing adequate nutrition and exercise.
After all, my own family is proof that children of short parents not only can end up taller than their mom and dad, but they can even surpass the national average for height of their sex.
You may also like to read:
- Can Sons Be Shorter Than Their Mothers? (Explained)
- What to Know About How a Son Should Treat His Father
Additional Sources and Follow-Up: