Since then many lines of evidence such as twin, adoption and family studies have estimated the role of genetic factors in the determination of height, showing that it is one of the most heritable human quantitative phenotypes 4.
Interest in the genetic influences on height was renewed when genetic linkage studies enabled research into genetic effects over the whole genome 5 and genome-wide association GWA studies allowed identification of loci consistently associated with height in populations of different ancestry 6 , 7 , 8 , 9 , Beside the genetic factors, a multitude of environmental factors can affect height.
They can operate during the whole growth period, but infancy is probably the most sensitive phase regarding external influences 11 , In the presence of adverse environmental conditions, the physical growth of children can decline and even adult height be affected 12 , 13 , Nutrition and especially lack of dietary protein is universally the most important environmental factor influencing height, but also childhood diseases, in particular infections, can affect growth These and other proximate biological determinants are further associated with social and economic conditions manifesting as socio-economic differences in height both within and between populations Although the heritable nature of height has been recognized for more than one hundred years, only a few studies have explored in detail the genetic variation of height during childhood and adolescence.
Twin studies have consistently estimated that the heritability of height is lowest 0. However, these studies leave unclear whether environmental factors shared by co-twins, which are generally important in infancy and childhood, persist in adolescence or after the cessation of growth 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , Somewhat different results were observed in a longitudinal study of two Finnish twin cohorts, which found that common environmental factors affected height at different ages in adolescence and early adulthood Height is also a classic example of a sexually dimorphic trait; on average, men are taller than women in all human populations However, much less is known about sex-differences in genetic and environmental contributions to height variation.
Greater heritability estimates for males than for females in childhood 15 and adulthood 21 have been reported. Also sex-specific genetic effects have been found for height, but the results are inconsistent across studies 18 , 19 , 20 , 21 , Further, a greater mean height has been consistently observed in Western populations as compared with East-Asian populations 13 , but most studies on the genetic and environmental factors influencing height variation to date are based on Western populations.
A multinational study on adolescent twins from eight countries showed that even when the total variation of height was higher in Western populations, the heritability estimates were largely similar between Western and East-Asian populations Descriptive statistics of height by age and sex for the pooled data all cohorts together and by geographic-cultural region are presented in Table 1.
When comparing geographic-cultural regions, mean height was tallest in Europe, somewhat shorter in North-America and Australia and shortest in East-Asia at all ages in boys and girls. The variation of height showed a less clear pattern but was generally greatest in North-America and Australia and lowest in East-Asia.
The proportion of environmental variation shared by co-twins was greatest at age 1 0. Accordingly, heritability was lowest at age 1 0. The proportion of height variation explained by environmental factors unique to each twin individual, which also includes measurement error, did not show any clear age pattern and was largely similar at all ages 0. In spite of the observed sex differences in the relative variance components at most of ages See Supplementary Table S2 , the age pattern was generally similar in boys and girls; the biggest sex-differences were found in late adolescence when the heritability estimates were slightly greater in boys.
The point estimates for the genetic correlations within opposite-sex DZ pairs were generally lower than 0. Univariate models for height were then conducted separately in the three geographic-cultural regions. Only the estimates of additive genetic factors are presented in Fig. The three geographic-cultural regions showed the general trend of increasing proportion of additive genetic factors with age during childhood. Explained by its largest sample size, the pattern in Europe was practically the same to that observed for all cohorts together, but with slightly greater heritability estimates at most ages.
In North-America and Australia and East-Asia, heritability estimates in childhood were generally somewhat lower than in Europe. In spite of the roughly similar age patterns, the proportions of height variation explained by genetic and environmental factors were different between the geographic-cultural regions See Supplementary Table S2.
The Chinese National Twin Registry was excluded from these analyses because the heritability estimates in that cohort were substantially lower than in other East-Asian cohorts. When data from this cohort was included in the analyses for East-Asia, the proportion of genetic factors decreased and common environmental factors increased considerably; the change in heritability estimates was from 0.
Finally, we studied how age modifies the genetic and environmental variances of height by using gene-age interaction analysis, with data pooled across all age groups. When stratified by geographic-cultural region, genetic variation was largest in North-America and Australia, somewhat lower in Europe and lowest in East-Asia, particularly for boys.
The pattern of genetic variance increasing to a maximum and thereafter decreasing was consistent across the regions. Unique environmental variation showed a similar pattern and magnitude in the three geographic-cultural regions. When comparing sexes, in Europe and North-America and Australia there was a trend toward a greater genetic variation for boys than for girls, which increased with age.
Change of additive genetic dash line , common environmental solid line and unique environmental dot line variance with increasing age in quadratic gene-environment interaction model in Europe, North America and Australia and East Asia. The present study of , paired measurements from 86, complete twin pairs in 20 countries revealed that environmental factors shared by co-twins contribute to the inter-individual variation in height from infancy to early adulthood.
The relative proportion of common environmental factors was greatest during the first years of life, representing almost half of the variation at age 1 and decreased over childhood and adolescence. The interpretation of these results, however, deserves some caution. It has been questioned whether twin studies are suitable for estimating heritability of height in infancy, since early growth patterns in twins differ considerably from singleton growth patterns Prenatal environmental factors can act very differently on MZ twins leading to differences in body size within pairs the most extreme case is the twin-to-twin transfusion syndrome.
This is an important issue because in the classical twin design heritability is estimated by comparing the resemblance of MZ and DZ twin pairs and thus body size differences in MZ pairs will result in lower heritability estimates. Since children may take several years to fully catch-up after birth, the high proportion of height variation explained by the shared environment in infancy may still reflect these prenatal environmental factors.
Among other possible explanations, it might be that the shared environment represents the effects of gestational age or the effects of the higher measurement error correlated in twins at earlier ages. Studies have shown that the secular trend in adult height occurs during the first two years of life mainly due to increases in leg length A plausible explanation is that the period of most rapid growth, when the effect of an adverse environment is strongest, coincides with the period when most growth takes place in the long bones of the legs Multinational studies analyzing the genetic and environmental influences on body length segments, particularly leg length, are thus needed to disentangle the aetiology of total height variation.
The small but considerable effect of unique environment on height variation, very similar across ages, may partly be due to measurement error, which is modelled as part of unique environmental factors. However, it is likely that it also reflects real environmental factors, for example, different exposure to childhood diseases.
Given the rapid growth that occurs in infancy, childhood and adolescence, in this individual-based pooled analysis we analyzed the heritability of height in one year age groups. We found that genetic contributions increase over childhood with heritability estimates in the range of previous studies in children and adults 15 , 16 , 18 , 20 , GWA studies have identified many common genetic variants for adult height. The most recent GWA meta-analysis in , individuals of European ancestry identified genome-wide significant SNPs in loci that together explained one-fifth of the heritability for adult height However, much less is known on the genetics of height in children.
Van der Valk et al. The pattern of total height variation across ages was largely driven by genetic variance. After that point, even if mean height continued to increase, genetic variance started to decrease in such a way that in late adolescence the magnitude was similar to that before pubertal events start.
Adolescence is characterized by the onset of puberty and the occurrence of growth spurts. In this study, twins within age groups are at various stages of puberty. In addition to the substantial heritability reported for pubertal timing 32 , a genome-wide genetic correlation 0.
In fact, a genome-wide association meta-analysis showed that five loci associated with pubertal timing impacted multiple aspects of growth, both before and during puberty Therefore, it is possible that some of the genetic variance in height at these ages is confounded with genetic variance in pubertal events. In spite of the largely similar age patterns observed in boys and girls, boys showed somewhat greater heritability estimates and genetic variation, especially in late adolescence.
Moreover, some studies have shown a sex-specific genetic effect on height variation in adolescents 19 and adults It is clear that both of the sex chromosomes are implicated in determining mean height. Short stature has been demonstrated in females with Turner syndrome who have only one X chromosome 35 and taller stature seen in XYY men compared with XY men However, sex chromosomes have also been associated with height variation; for example, Gudbjartsson et al.
Comparison between geographic-cultural regions showed that mean height was greatest in Europe, somewhat shorter in North-America and Australia and shortest in East-Asia, but total variance was largest in North-America and Australia. Accordingly, genetic variation was also greatest in North-America and Australia and lowest in East-Asia. However, the relative proportions of additive and environmental variations were more similar in the different geographic-cultural regions.
These results are consistent with a previous comparative twin study which found that the mean and variance of height were larger in Caucasian than in East-Asian populations in adolescence, but the heritability estimates were still at the same level An important proportion of the differences in total variances between geographic-cultural regions were attributable to genetic differences. It may be that allelic frequencies and effects of the genes involved in height vary between Europeans, North-Americans and Australians and East-Asians, leading to differences in genetic variation between the three population groups.
However, a major part of the differences in genetic variation may also be because of gene-environment interactions modelled as part of the additive genetic component in our model. That is, the higher genetic variation observed in Caucasians could arise because there is a set of genes expressed more strongly in Western environments.
For example, a study of adults of Japanese descent living in the United States and native Japanese found that Japanese men and women were shorter than Japanese-Americans, suggesting that environmental factors play a role in physical growth Analyzing this question in detail would require collection of twins or GWA studies in unrelated individuals with East-Asian origin living in a Western environment.
However, our study found that shared environmental variance also differed between geographic-cultural regions. To accurately measure how genetically similar relatives are, one can measure the number of genetic markers they share.
For example, Peter M. Visscher of the Queensland Institute of Medical Research in Australia recently reported that the heritability of height is 80 percent, based on 3, pairs of Australian twins and siblings. This estimate is considered to be unbiased, as it was based on a large population of twins and siblings and a broad survey of genetic markers.
In the U. These estimates are well supported by another study of 8, pairs of Finnish twins, in which the heritability was 78 percent for men and 75 percent for women. Other studies have shown height heritability among whites to be even higher than 80 percent. Because different ethnic populations have different genetic backgrounds and live in different environments, however, height heritability can vary from one population to another, and even from men to women. In Asian populations, the heritability of height is much lower than 80 percent.
For example, in Miao-Xin Li of Hunan Normal University in China and his colleagues estimated a height heritability of 65 percent, based on a Chinese population of families. In African populations, height heritability is also lower: 65 percent for the population of western Africa, according to a study by D.
Roberts, then at Newcastle University in England, and colleagues. Such diversities in heritability are mainly due to the different genetic background of ethnic groups and the distinct environments climates, dietary habits and lifestyle they experience.
Heritability allows us to examine how genetics directly impact an individual's height. For example, a population of white men has a heritability of 80 percent and an average height of centimeters roughly five feet, 10 inches.
If we meet a white man in the street who is cm six feet tall, the heritability tells us what fraction of his extra height is caused by genetic variants and what fraction is due to his environment dietary habit and lifestyle.
The man is five centimeters taller than the average. A bone-shortening surgery may reduce your height, but it's more commonly done to…. Although height depends largely on genetics, getting enough nutrients is essential to ensuring proper growth and development. Here are 11 foods that….
Learn about possible causes and treatments. Plenty of stories abound online providing advice for getting a defined or chiseled jawline.
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Is Height Genetic? Yes and No. Genetics Other factors Can you increase height? Interestingly, the age of menarche, which is also influenced by nutrition, has shown a corresponding decrease over this same time period. Some scientists believe that the increase in teenage and out-of-wedlock pregnancies in the developed world may be an unanticipated consequence of improved nutrition. Third, conditions of poor nutrition are well correlated to smaller stature. For example, the heights of all classes of people, from factory workers to the rich, increased as food quality, production and distribution became more reliable, although class differences still remain.
Even more dramatic, the heights of vagrant London boys declined from to and then rose three inches in just 30 years--an increase that paralleled improving conditions for the poor. Even today, height is used in some countries as an indicator of socioeconomic division, and differences can reveal discrimination within social, ethnic, economic, occupational and geographic groups. For those hoping that humans might someday shoot basketballs through foot high hoops, the fact that the increase in human height is leveling off no doubt will be disappointing.
For those who understand, however, that our genes are merely a blueprint that specifies what is possible given an optimal environment, a limit on height is just one of many limitations in life, and certainly not the most constraining. With environmental variables perhaps near their optimum, what are the prospects for evolutionary increases in height as a consequence of changes to our genetic blueprints? Apply the methods of the thought experiment above and see. Already a subscriber?
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