Human height in the context of "Quantitative traits"

In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics it usually refers to the degree to which a pair of variables are linearly related. Familiar examples of dependent phenomena include the correlation between the height of parents and their offspring, and the correlation between the price of a good and the quantity the consumers are willing to purchase, as it is depicted in the demand curve.

Correlations are useful because they can indicate a predictive relationship that can be exploited in practice. For example, an electrical utility may produce less power on a mild day based on the correlation between electricity demand and weather. In this example, there is a causal relationship, because extreme weather causes people to use more electricity for heating or cooling. However, in general, the presence of a correlation is not sufficient to infer the presence of a causal relationship (i.e., correlation does not imply causation).

Arm span or reach (sometimes referred to as wingspan, or spelled armspan) is the physical measurement of the length from one end of an individual's arms (measured at the fingertips) to the other when raised parallel to the ground at shoulder height at a 90° angle. The arm span measurement is usually very close to the person's height. Age, sex, and ethnicity have to be taken into account to best predict height from arm span. Arm span is sometimes used when a height measurement is needed but the individual cannot stand on a traditional stadiometer or against a wall due to abnormalities of the back or legs, such as scoliosis, osteoporosis, amputations, or those who are confined to a bed or wheelchair. Other, possibly more accurate measuring techniques include knee length or recumbent length when possible.

Because any decrease in height will cause an increase in the ratio of arm span to height, a large span to height ratio may sometimes be an indicator of a health problem that caused a vertical height loss such as postural changes due to ageing or any spinal conditions such as degenerative disc disease.

A centimetre (International spelling) or centimeter (American English), with SI symbol cm, is a unit of length in the International System of Units (SI) equal to one hundredth of a metre, centi- being the SI prefix for a factor of ⁠1/100⁠. Equivalently, there are 100 centimetres in 1 metre. The centimetre was the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units.

Though for many physical quantities, SI prefixes for factors of 10—like milli- and kilo-—are often preferred by technicians, the centimetre remains a practical unit of length for many everyday measurements; for instance, human height is commonly measured in centimetres. A centimetre is approximately the width of the fingernail of an average adult person.

Forensic anthropology is the application of the anatomical science of anthropology and its various subfields, including forensic archaeology and forensic taphonomy, in a legal setting. A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated or otherwise unrecognizable, as might happen in a plane crash. Forensic anthropologists are also instrumental in the investigation and documentation of genocide and mass graves. Along with forensic pathologists, forensic dentists, and homicide investigators, forensic anthropologists commonly testify in court as expert witnesses. Using physical markers present on a skeleton, a forensic anthropologist can potentially determine a person's age, sex, stature, and race. In addition to identifying physical characteristics of the individual, forensic anthropologists can use skeletal abnormalities to potentially determine cause of death, past trauma such as broken bones or medical procedures, as well as diseases such as bone cancer.

The methods used to identify a person from a skeleton relies on the past contributions of various anthropologists and the study of human skeletal differences. Through the collection of thousands of specimens and the analysis of differences within a population, estimations can be made based on physical characteristics. Through these, a set of remains can potentially be identified. The field of forensic anthropology grew during the twentieth century into a fully recognized forensic specialty involving trained anthropologists as well as numerous research institutions gathering data on decomposition and the effects it can have on the skeleton.

Height discrimination is prejudice or discrimination against individuals based on height. In principle, it refers to the discriminatory treatment against individuals whose height is not within the normal acceptable range of height in a population. Various studies have shown it to be a cause of bullying, commonly manifested as unconscious microaggressions.

Modern Western height discrimination originated in 19th century eugenic, Social Darwinist, and white supremacist movements, beginning with eugenicist Sir Francis Galton's observation of the correlation of human height between parents and offspring. These movements promulgated pseudoscientific beliefs about the superiority of larger male stature, most grotesquely embodied by the Nazi height ideals within the social construct of the Aryan master race.

Complex traits are phenotypes that are controlled by two or more genes and do not follow Mendel's Law of Dominance. They may have a range of expression which is typically continuous. Both environmental and genetic factors often impact the variation in expression. Human height is a continuous trait meaning that there is a wide range of heights. There are an estimated 50 genes that affect the height of a human. Environmental factors, like nutrition, also play a role in a human's height. Other examples of complex traits include: crop yield, plant color, and many diseases including diabetes and Parkinson's disease. One major goal of genetic research today is to better understand the molecular mechanisms through which genetic variants act to influence complex traits. Complex traits are also known as polygenic traits and multigenic traits.

The existence of complex traits, which are far more common than Mendelian traits, represented a significant challenge to the acceptance of Mendel's work. Modern understanding has 3 categories of complex traits: quantitative, meristic, and threshold. These traits have been studied on a small scale with observational techniques like twin studies. They are also studied with statistical techniques like quantitative trait loci (QTL) mapping, and genome-wide association studies (GWAS) on a large scale. The overall goal of figuring out how genes interact with each other and the environment and how those interactions can lead to variation in a trait is called genetic architecture.