Is there any scientific evidence that in humans males are taller than females? And if so, what is the reason that they are taller (please include genes or hormones that accounts for human growth and how they are affected in males and females)?
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$\begingroup$ I assume that you are talking about humans only, and would suggest to edit the question accordingly - I do not think this is entirely clear from the wording of the actual question. This is relevant, as in many other species, females are taller/bigger than males. $\endgroup$– GerhardApr 25, 2016 at 6:46
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$\begingroup$ @Gerhard the question was migrated from the health website. My questions is comparing human males and females. $\endgroup$– shnisakaApr 25, 2016 at 6:49
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$\begingroup$ Ah, that explains it ;) But I'd suggest to edit the question anyways, eg. by using "women" and "men" instead. $\endgroup$– GerhardApr 25, 2016 at 6:50
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1 Answer
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Are males taller than females?
Best data I could find come from the Statistical Abstract of the United States (1999) > Section 3. Here is a table reporting the percentage of the male and female population which height is lower than a given threshold
Note that this data collection was done among students in US universities and is therefore not representative of the whole world or even the whole country.
Does height follow a bimodal distribution?
A difference in height between males and females is often used as a classical example in introductory statistic class to exemplify a bimodal distribution as seen in this picture
and on these (a priori fake) data
However, Schilling et al. 2002 argued that while the difference in mean height between the sexes is real, this difference is too small relative to the variance in height within each sex to be clearly depicted on a graph.
Note that I found this non-peer-reviewed paper which shows real data that display a truly bimodal distribution of height.
Genetics of height
The question why are they taller? is very broad. I will just focus to give you some hints about the genetics of height in humans. First, you want to make sure you understand the concept of heritability.
Evoy and Vissher 2009 report a heritability coefficient of 0.8. This estimate is impressively high - only a few phenotypic traits have such high heritability. They also review articles discussing that 50 loci are correlated with variation in height (actually, today, more than 500 loci are known to contribute to height, see the link in AlexDeLarge's comment to this answer). However, these loci are not sufficient to explain the whole heritability observed (common missing heritability issue). Yang et al. 2010 provide evidence that the remaining heritability is due to incomplete linkage disequilibrium between causal variants and loci of weak effects. In short, height is a highly polygenic trait.
Related post
You should have a look at Is there a genetic reason explaining the difference of the height of male and female? for more information.
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1$\begingroup$ +1 for the answer to the first part of the question, but the second needs work; differences in height due to sex are probably primarily due to development rather than genetics (males and females are fairly well-mixed populations...). This paper describes one developmental mechanism (sex-based differences in GH-dependent STAT5b regulation of IGF-I expression): ncbi.nlm.nih.gov/pubmed/15506072. It also discusses selective pressures for sexual dimorphism in humans versus other species, which could be another part of the answer to the "reasons" part of the question. $\endgroup$ Apr 25, 2016 at 9:47
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1$\begingroup$ @shnisaka: You might also want to take a look at my answer to this question about the genetic basis for height difference in human males and females. $\endgroup$ May 15, 2017 at 14:26
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1$\begingroup$ @AlexDeLarge Thanks for the link. I added it to the answer. $\endgroup$– Remi.bMay 15, 2017 at 16:08