Height is a trait that frequently generates curiosity about its origins, especially regarding the relative contributions of a child’s mother and father. Estimates suggest that up to 80% of the variation in human height is influenced by genetic factors, underscoring the strong biological control over final adult height. While the common question seeks a simple answer—a single “height gene”—the reality is far more complex than a straightforward maternal or paternal inheritance pattern. Understanding how height is determined requires looking beyond single genes and examining the cumulative effect of hundreds of variants interacting with the environment.
Height is Determined by Both Parents
The direct answer to where the height gene comes from is that it is equally inherited from both parents. Human DNA is organized into 23 pairs of chromosomes, and height is determined almost entirely by genes located on the 22 pairs of non-sex chromosomes, known as autosomes. A child receives one full set of 22 autosomes from the mother and one full set from the father, resulting in an equal genetic contribution to the raw material for height. While some genes that regulate growth hormones are located on the X chromosome, the overwhelming majority of genetic influences on height are autosomal, preventing a scenario where one parent’s height genetics dominate. A child’s final height reflects this combined genetic potential, which is why tall parents generally have tall children and shorter parents have shorter children.
The Polygenic Nature of Height
Height is a classic example of a complex trait, meaning it is polygenic, influenced by many genes working together. Instead of one or two “master” height genes, hundreds of common gene variants each contribute a tiny, additive effect to a person’s final height. These variants are typically single nucleotide polymorphisms (SNPs), which are locations in the genome where a single letter of the DNA code varies among individuals. Modern genetic research, particularly large-scale Genome-Wide Association Studies (GWAS), has identified thousands of these genetic variants associated with height. One study analyzing the DNA of millions of people identified over 12,000 such spots in the genome that influence stature. The genetic contribution is a cumulative score based on the specific combination of variants inherited from both parents. This explains why a child can be taller or shorter than either parent; they may inherit a particularly advantageous or disadvantageous collection of these small-effect variants from both sides of the family. The sheer complexity of this additive genetic architecture makes predicting height based on genetics a matter of probabilities rather than absolutes.
Non-Genetic Factors Influencing Stature
While genetics account for a large portion of height variation, an estimated 20% to 40% of the variance is attributed to non-genetic, or environmental, factors. The most significant environmental factor is nutrition, especially during the rapid growth periods of infancy and adolescence. A sufficient and balanced intake of macronutrients like protein is necessary, as amino acids are the building blocks for the tissues and bones that lengthen during growth.
Micronutrients are also important, with deficiencies in Vitamin D and calcium directly impacting bone density and growth plate development. A lack of these nutrients, particularly in early childhood, can lead to growth impairment even if the child has a high genetic potential for tallness. Childhood health is another modifier, as chronic illness or repeated, severe infections can divert energy and resources away from growth. Conditions that affect the endocrine system, such as untreated thyroid or growth hormone deficiencies, can severely limit skeletal growth regardless of parental height. Socioeconomic factors, which influence access to consistent, high-quality nutrition and medical care, play a subtle but measurable role in determining the final adult height achieved within a population.
Calculating Expected Adult Height
Since genetics provide the foundation for height, parents often seek a practical method to estimate their child’s final adult stature. Pediatricians commonly use the Mid-Parental Height (MPH) calculation to determine a child’s genetically expected target height. The MPH calculation uses a straightforward formula that accounts for the average height difference between sexes, which is approximately 5 inches (or 13 centimeters).
The calculation involves four steps:
- Add the mother’s and father’s heights together.
- For a boy, add 5 inches (13 cm) to that sum.
- For a girl, subtract 5 inches (13 cm) from that sum.
- Divide the resulting total by two to find the MPH.
This resulting number is not a guarantee but represents the statistical center of the child’s predicted adult height range. The actual final height is expected to fall within a range of approximately two to four inches above or below the calculated MPH, reflecting the thousands of random gene combinations and environmental variables at play. The MPH serves primarily as a screening tool to assess whether a child’s current growth pattern is consistent with their genetic inheritance or if a growth disorder might be present.