Editing Human height (section)

== Determinants of growth ==
[[File: Human height growth per month, United States.png|thumb|upright=2|The median (50th percentile) growth curves for males and females 0−20 years in the United States]]

The study of height is known as ''[[auxology]]''.<ref>Hermanussen, Michael (ed) (2013) ''Auxology – Studying Human Growth and Development'', Schweizerbart, {{ISBN|9783510652785}}.</ref>

Growth has long been recognized as a measure of the [[health]] of individuals, hence part of the reasoning for the use of [[growth chart]]s. For individuals, as indicators of health problems, growth trends are tracked for significant deviations, and growth is also monitored for significant deficiency from genetic expectations. Genetics is a major factor in determining the height of individuals, though it is far less influential regarding differences among populations. Average height is relevant to the measurement of the health and wellness [[standard of living]] and [[quality of life]] of populations.<ref>{{Cite journal | last1 = Bolton-Smith | first1 = C. | title = Accuracy of the estimated prevalence of obesity from self reported height and weight in an adult Scottish population | doi = 10.1136/jech.54.2.143 | journal = Journal of Epidemiology & Community Health | volume = 54 | issue = 2 | pages = 143–148 | year = 2000 | pmid =  10715748 | pmc = 1731630}}</ref>

{{anchor|Growth Spurt}}Humans grow fastest (other than in the womb) as [[infant]]s and [[toddler]]s, rapidly declining from a maximum at birth to roughly age 2, tapering to a slowly declining rate, and then, during the [[pubertal]] growth spurt (with an average girl starting her puberty and pubertal growth spurt at 10 years<ref>{{cite web |title=Early Puberty in Girls |url=https://www.nationwidechildrens.org/conditions/early-puberty-in-girls |website=Nationwide Children's |access-date=5 June 2020}}</ref> and an average boy starting his puberty and pubertal growth spurt at 12 years<ref>{{cite web |title=Early Puberty in Boys |url=https://www.nationwidechildrens.org/conditions/early-puberty-in-boys |website=Nationwide Children's |access-date=5 June 2020}}</ref><ref>{{cite web |title=Is Your Child Growing Normally? |url=https://www.magicfoundation.org/Is-My-Child-Growing/ |website=THE MAGIC FOUNDATION |access-date=20 June 2020}}</ref>), a rapid rise to a second maximum (at around 11−12 years for an average female, and 13−14 years for an average male), followed by a steady decline to zero. The average female growth speed trails off to zero at about 15 or 16 years, whereas the average male curve continues for approximately 3 more years, going to zero at about 18−19, although there is limited research to suggest minor height growth after the age of 19 in males.<ref>{{Cite journal |last1=Hulanicka |first1=B. |last2=Kotlarz |first2=K. |date=1983 |title=The final phase of growth in height |url=https://pubmed.ncbi.nlm.nih.gov/6638938/ |journal=Annals of Human Biology |volume=10 |issue=5 |pages=429–433 |doi=10.1080/03014468300006621 |issn=0301-4460 |pmid=6638938}}</ref> These are also critical periods where stressors such as malnutrition (or even severe [[child neglect]]) have the greatest effect.

Moreover, the health of a mother throughout her life, especially during her critical period and [[pregnancy]], has a role. A healthier child and adult develops a body that is better able to provide optimal prenatal conditions.<ref name="grantham2007" /> The pregnant mother's health is essential for herself but also the fetus as [[gestation]] is itself a critical period for an [[embryo]]/[[fetus]], though some problems affecting height during this period are resolved by catch-up growth assuming childhood conditions are good. Thus, there is a cumulative generation effect such that nutrition and health over generations influence the height of descendants to varying degrees.

The age of the mother also has some influence on her child's height. Studies in modern times have observed a gradual increase in height with maternal age, though these early studies suggest that trend is due to various socio-economic situations that select certain demographics as being more likely to have a first birth early in the mother's life.<ref>[http://www.nature.com/ejcn/journal/v57/n1/fig_tab/1601508t1.html#figure-title Table 1. Association of 'biological' and demographic variables and height. Figures are coefficients (95% confidence intervals) adjusted for each of the variables shown] in {{Cite journal|vauthors=Rona RJ, Mahabir D, Rocke B, Chinn S, Gulliford MC |title=Social inequalities and children's height in Trinidad and Tobago |journal=European Journal of Clinical Nutrition |volume=57 |issue=1 |pages=143–50 |year=2003 |pmid=12548309 |doi=10.1038/SJ.ejcn.1601508|doi-access=free }}</ref><ref name="IFPP">{{Cite journal |title=Birth Outcomes by Mother's Age At First Birth in the Philippines |first1=Jane E. |last1=Miller |year=1993 |journal=International Family Planning Perspectives |volume=19 |issue=3 |pages=98–102 |doi=10.2307/2133243 |jstor=2133243}}</ref><ref name="ISER">{{Cite journal|url=https://ideas.repec.org/p/ese/iserwp/2003-31.html|title=Outcomes in Childhood and Adulthood by Mother's Age at Birth: evidence from the 1970 British Cohort Study|first=David J. |last=Pevalin |journal=ISER Working Papers |year=2003}}</ref> These same studies show that children born to a young mother are more likely to have below-average educational and behavioural development, again suggesting an ultimate cause of resources and family status rather than a purely biological explanation.<ref name="IFPP" /><ref name="ISER" />

In 1988, it was observed that first-born males were shorter than later-born males.<ref>{{Cite journal| doi = 10.1080/03014468800009581| last1 = Hermanussen | first1 = M.| last2 = Hermanussen | first2 = B.| last3 = Burmeister | first3 = J.| title = The association between birth order and adult stature| journal = Annals of Human Biology| volume = 15| issue = 2| pages = 161–165| year = 1988| pmid = 3355105}}</ref> However, in 2013, the reverse observation was made.<ref>{{cite journal|last1=Myrskyla|first1=M|title=The association between height and birth order: evidence from 652,518 Swedish men.|journal=Journal of Epidemiology and Community Health|date=July 2013|volume=67|issue=7|pages=571–7|pmid=23645856|doi=10.1136/jech-2012-202296|s2cid=19510422|url=https://google.com}}</ref> The study authors suggest that the cause may be socioeconomic in nature.

===Genetics ===
The precise relationship between [[nature versus nurture|genetics and environment]] is complex and uncertain. Differences in human height is 60−80% [[Heritability|heritable]], according to several [[twin study|twin studies]]<ref>{{cite journal|url=https://www.scientificamerican.com/article/how-much-of-human-height/|title=How much of human height is genetic and how much is due to nutrition? |author=Lai, Chao-Qiang |journal=Scientific American|date=11 December 2006}}</ref> and has been considered [[polygenic]] since the [[Mendelian-biometrician debate|Mendelian–biometrician debate]] a hundred years ago. A genome-wide association (GWA) study of more than 180,000 individuals has identified hundreds of genetic variants in at least 180 loci associated with adult human height.<ref>{{cite journal|title=Hundreds of variants clustered in genomic loci and biological pathways affect human height|journal=Nature|year=2010|issue=7317|pages= 832–838 |vauthors=Lango Allen H, etal |volume=467|doi=10.1038/nature09410|pmid=20881960|pmc=2955183|bibcode=2010Natur.467..832L}}</ref> The number of individuals has since been expanded to 253,288 individuals and the number of genetic variants identified is 697 in 423 genetic loci.<ref>{{cite journal|title=Defining the role of common variation in the genomic and biological architecture of adult human height|journal=Nature Genetics|year=2014|issue=11|pages=1173–1186 |vauthors=Wood AR, etal |pmid=25282103|doi=10.1038/ng.3097|volume=46|pmc=4250049}}</ref> In a separate study of [[body proportion]] using sitting-height ratio, it reports that these 697 variants can be partitioned into three specific classes: (1) variants that primarily determine leg length, (2) variants that primarily determine spine and head length, or (3) variants that affect overall body size. This gives insights into the biological mechanisms underlying how these 697 genetic variants affect overall height.<ref>{{cite journal|title=Genome-wide Analysis of Body Proportion Classifies Height-Associated Variants by Mechanism of Action and Implicates Genes Important for Skeletal Development|journal=American Journal of Human Genetics|year=2015 |vauthors=Chan Y, etal |pmid=25865494|doi=10.1016/j.ajhg.2015.02.018|volume=96|issue=5|pages=695–708|pmc=4570286}}</ref> These loci do not only determine height, but other features or characteristics. As an example, 4 of the 7 loci identified for intracranial volume had previously been discovered for human height.<ref>{{Cite journal|last1=Adams|first1=Hieab H H|last2=Hibar|first2=Derrek P|last3=Chouraki|first3=Vincent|last4=Stein|first4=Jason L|last5=Nyquist|first5=Paul A|last6=Rentería|first6=Miguel E|last7=Trompet|first7=Stella|last8=Arias-Vasquez|first8=Alejandro|last9=Seshadri|first9=Sudha|year=2016|title=Novel genetic loci underlying human intracranial volume identified through genome-wide association|journal=Nature Neuroscience|volume=19|issue=12|pages=1569–1582|doi=10.1038/nn.4398|pmid=27694991|pmc=5227112}}</ref>
Height, like other [[phenotypic]] traits, is determined by a combination of [[genetics]] and [[environmental factor]]. A child's height based on parental heights is subject to [[regression toward the mean]], therefore extremely tall or short parents will likely have correspondingly taller or shorter offspring, but their offspring will also likely be closer to average height than the parents themselves. Genetic potential and several hormones, minus illness, is a basic determinant for height. Other factors include the genetic response to external factors such as diet, exercise, environment, and life circumstances.{{citation needed|date=March 2024}}

===Environmental and epigenetic effects===
The effect of environment on height is illustrated by studies performed by anthropologist [[Barry Bogin]] and coworkers of Guatemala Mayan children living in the United States. In the early 1970s, when Bogin first visited [[Guatemala]], he observed that [[Mayan peoples|Mayan]] [[Indigenous people of the Americas#Guatemala|Indian]] men averaged {{convert|157|cm|ftin|abbr=on}} in height and the women averaged {{convert|142|cm|ftin|abbr=on}}. Bogin took another series of measurements after the [[Guatemalan Civil War]], during which up to a million Guatemalans fled to the United States. He discovered that Maya refugees, who ranged from six to twelve years old, were significantly taller than their Guatemalan counterparts.<ref>{{Cite journal | volume = 19 | issue = 2 | pages = 40–44 | last = Bogin | first = Barry | title = The tall and the short of it | journal = Discover | access-date = 26 April 2013 | year = 1998 | url = https://growtallernatural.com/tallshort }}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> By 2000, the American Maya were {{convert|10.24|cm|in|1}} taller than the Guatemalan Maya of the same age, largely due to better nutrition and [[health care]].<ref name="bogin2003" /> Bogin also noted that American Maya children had relatively longer legs, averaging {{convert|7.02|cm|in|1}} longer than the Guatemalan Maya (a significantly lower sitting height ratio).<ref name=bogin2003>{{Cite journal | last1 = Bogin | first1 = B. | last2 = Rios | first2 = L. | doi = 10.1016/S1095-6433(02)00294-5 | title = Rapid morphological change in living humans: Implications for modern human origins | journal = Comparative Biochemistry and Physiology A | volume = 136 | pages = 71–84 | year = 2003 | pmid =  14527631| issue=1}}</ref><ref>{{cite web |author=Krawitz, Jan |url=https://www.pbs.org/pov/pov2005/bigenough/special_heightgap_04.html |title=P.O.V. - Big Enough |publisher=PBS |date=28 June 2006 |access-date=22 January 2011 |archive-date=30 April 2009 |archive-url=https://web.archive.org/web/20090430043527/http://www.pbs.org/pov/pov2005/bigenough/special_heightgap_04.html |url-status=dead }}</ref>

The [[Nilotic]] peoples of Sudan such as the [[Shilluk people|Shilluk]] and [[Dinka]] have been described as some of the tallest in the world. Dinka Ruweng males investigated by Roberts in 1953−1954 were on average {{convert|181|cm|ftin|abbr=on}} tall, and Shilluk males averaged {{convert|182|cm|ftin|abbr=on}}.<ref>{{Cite journal | last1 = Roberts | first1 = D. F. | last2 = Bainbridge | first2 = D. R. | doi = 10.1002/ajpa.1330210309 | title = Nilotic physique | journal = American Journal of Physical Anthropology | volume = 21 | issue = 3 | pages = 341–370 | year = 1963 | pmid =  14159970}}</ref> The Nilotic people are characterized as having long legs, narrow bodies and short trunks, an adaptation to hot weather.<ref>{{cite journal|page=26 |journal=Planet Earth |date=Summer 2006 |url=http://www.nerc.ac.uk/publications/planetearth/2006/summer/sum06-skeleton.pdf |title=Skeleton key |author=Stock, Jay |url-status=dead |archive-url=https://web.archive.org/web/20070810003347/http://www.nerc.ac.uk/publications/planetearth/2006/summer/sum06-skeleton.pdf |archive-date=10 August 2007 |df=dmy-all }}</ref> However, male Dinka and Shilluk refugees measured in 1995 in Southwestern Ethiopia were on average only {{convert|176|cm|ftin|abbr=on}} and {{convert|172|cm|ftin|abbr=on}} tall, respectively. As the study points out, Nilotic people "may attain greater height if privileged with favourable environmental conditions during early childhood and adolescence, allowing full expression of the genetic material."<ref>{{Cite journal|author=Chali D |title=Anthropometric measurements of the Nilotic tribes in a refugee camp |journal=Ethiopian Medical Journal |volume=33 |issue=4 |pages=211–7 |year=1995 |pmid=8674486}}</ref> Before fleeing, these refugees were subject to [[Refugees of Sudan#Displacement|privation]] as a consequence of the [[First Sudanese Civil War|succession of civil wars]] in their country from 1955 to the present.

Attributed as a significant reason for the trend of increasing height in parts of Europe are the egalitarian populations where proper [[Health care|medical care]] and adequate nutrition had been relatively equally distributed as of 2004.<ref name=kolmos2004>{{Cite journal | last1 = Komlos | first1 = J. | last2 = Baur | first2 = M. | doi = 10.1016/j.ehb.2003.12.006 | title = From the tallest to (one of) the fattest: The enigmatic fate of the American population in the 20th century | journal = Economics & Human Biology | volume = 2 | pages = 57–74 | year = 2004 | pmid =  15463993| issue=1| citeseerx = 10.1.1.651.9270 | s2cid = 14291466 }}</ref> The uneven distribution of nutritional resources makes it more plausible for individuals with better access to resources to grow taller, while individuals with worse access to resources have a lessened chance of growing taller.<ref>{{Cite journal|last1=Baten|first1=Joerg|last2=Moradi|first2=Alexander|date=2005|title=Inequality in Sub-Saharan Africa: New Data and New Insights from Anthropometric Estimates|journal=World Development|volume=33|issue=8|pages=1233–1265|doi=10.1016/j.worlddev.2005.04.010}}</ref>

Changes in [[Diet (nutrition)|diet]] (nutrition) and a general rise in quality of health care and standard of living are the cited factors in Asian populations. Malnutrition including chronic undernutrition and acute malnutrition is known to have caused [[stunted growth]] in various populations.<ref>{{Cite journal | last1 = De Onis | first1 = M. | last2 = Blössner | first2 = M. | last3 = Borghi | first3 = E. | doi = 10.1017/S1368980011001315 | title = Prevalence and trends of stunting among pre-school children, 1990–2020 | journal = Public Health Nutrition | volume = 15 | issue = 1 | pages = 142–148 | year = 2011 | pmid =  21752311| doi-access = free }}</ref> This has been seen in North Korea, parts of Africa, certain historical Europe, and other populations.<ref name="grantham2007">{{Cite journal | last1 = Grantham-Mcgregor | first1 = S. | last2 = Cheung | first2 = Y. B. | last3 = Cueto | first3 = S. | last4 = Glewwe | first4 = P. | last5 = Richter | first5 = L. | last6 = Strupp | first6 = B. |author-link4=Paul Glewwe | doi = 10.1016/S0140-6736(07)60032-4 | title = Developmental potential in the first 5 years for children in developing countries | journal = The Lancet | volume = 369 | issue = 9555 | pages = 60–70 | year = 2007 | pmid =  17208643| pmc = 2270351}}</ref> [[Developing countries]] such as [[Guatemala]] have rates of stunting in children under 5 living as high as 82.2% in [[Totonicapán]], and 49.8% nationwide.<ref>{{Cite conference|publisher=Ministerio de Salud Pública y Asistencia Social |page=670 |title=Encuesta Nacional de Salud Materno Infantil, 2008-2009 |trans-title=Guatemala Reproductive Health Survey 2008‒2009 |location=Guatemala City, Guatemala |access-date=26 April 2013 |date=December 2010 |url=http://www.ine.gob.gt/np/ensmi/Informe_ENSMI2008_2009.pdf |url-status=dead |archive-url=https://web.archive.org/web/20111113153701/http://www.ine.gob.gt/np/ensmi/Informe_ENSMI2008_2009.pdf |archive-date=13 November 2011 |df=dmy }}</ref>

Average height in a nation is correlated with [[protein quality]]. Nations that consume more protein in the form of [[meat]], [[dairy]], [[egg (food)|eggs]], and [[fish]] tend to be taller, while those that obtain more protein from [[cereals]] tend to be shorter.{{citation needed|date=June 2018}} Therefore, populations with high cattle per capita and high consumption of dairy live longer and are taller. Historically, this can be seen in the cases of the United States, Argentina, New Zealand and Australia in the beginning of the 19th century.<ref>{{cite journal | last1=Baten | first1=Jörg | last2=Blum | first2=Matthias | year=2012 | title=An Anthropometric History of the World, 1810-1980: Did Migration and Globalization Influence Country Trends? | journal=Journal of Anthropological Sciences | volume=90 | issue=90 | pages=221–4 | doi=10.4436/jass.90011| doi-broken-date=1 November 2024 | pmid=23011935 | s2cid=38889880 |url=https://www.isita-org.com/jass/Contents/2012vol90/Baten/23011935.pdf }}</ref> Moreover, when the production and consumption of milk and beef is taken to consideration, it can be seen why the Germanic people who lived outside of the [[Roman Empire]] were taller than those who lived at its heart.<ref>{{Cite journal|last1=Baten|first1=Joerg|last2=Koepke|first2=Nikola|date=2008|title=Agricultural Specialization and Height in Ancient and Medieval Europe|journal=Explorations in Economic History|volume=45|issue=2|pages=127|doi=10.1016/j.eeh.2007.09.003}}</ref>