Why are boys taller than girls

Added: Antavius Branham - Date: 24.10.2021 00:39 - Views: 16185 - Clicks: 5990

Men are taller on average than women, but that may not be a trait that evolved through selection. One of the most obvious physical differences between men and women are their average sizes. Men are, on the whole, taller. But in a recent paper in Evolutionary AnthropologyDunsworth showed that the science points another way. She argued not only that the evidence that human body size is driven by sexual selection is quite flimsy but that a much better explanation has been hiding in plain sight in the medical and anthropological literature.

Human sexual size dimorphism, the difference in height between males and females, is often touted as a classic example of sexual selection: the kind of trait whose evolution was driven by differences in reproductive success rather than survival.

That is, even if sexual selection explains why male and female chimps differ in size, the human dimorphism could have more to do with their common ancestry with chimps than with a continuation of sexual selection. Dunsworth found a more direct explanation when she dug into the literature on bone biology and development, focusing in particular on how those relate to hormones. Ovaries matter because they produce a lot more estrogen than testes do, and estrogen helps direct bone development.

Before puberty, people with ovaries and people with testes grow at roughly the same rate.

Then those with ovaries ramp up estrogen production, which stimulates the growth plates in their bones and causes the long bones in particular to lengthen. Meanwhile, the bones of people with testes continue to grow for several years until their estrogen peaks, so they end up taller. This hormonal explanation fits well with historical shifts in human sexual size dimorphism. The increase in male height makes sense because people were presumably healthier and better fed after the pandemic, and adult height is strongly influenced by nutrition and health status during childhood.

But if women grew shorter, does that imply that they were less healthy after the plague? If so, the notable shift in sexual size dimorphism had nothing to do with competition.

The size difference was probably just a side effect of better health, and healthier people with ovaries start their periods earlier. Estrogen seemed as if it might explain how the height differences arose but not the deeper evolutionary question of why. But that framing can be misleading, Dunsworth counters. Because men are taller than women for a direct physiological reason — the bone growth effects of estrogen —anything affecting the degree or timing of estrogen levels will inevitably influence human sexual size dimorphism, even if that was not an effect that nature was selecting.

Any circumstances that led to earlier menarche would decrease the relative size of females incidentally, without any change to mating system or male-male competition level or, indeed, any rationale for the size change at all. And that means human sexual size dimorphism likely did evolve in the absence of sexual selection. So to understand why men are taller than women, we may need to understand why we experience puberty when we do and what drives differences in estrogen use between primates.

She also points out that the common hypothesis about why female pelvises are wider than male pelvises — that females need to give birth to big-brained babies — is similarly flawed. Much like long bone growth, pelvis width is driven largely by estrogen levels. The fact that simple anatomical reasons for hip-width differences were overlooked for so long points to systemic issues with the inclusivity of science, she said.

And while such stories can be appealing because they seem to make sense, they have real consequences in our everyday lives. Boys will be boys.

But our bones likely tell a very different story. Quanta Magazine moderates comments to facilitate an informed, substantive, civil conversation. Abusive, profane, self-promotional, misleading, incoherent or off-topic comments will be rejected. Moderators are staffed during regular business hours New York time and can only accept comments written in English.

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Abstractions blog Males Are the Taller Sex. By Christie Wilcox June 8, To explain why men are on average taller than women, scientists theorized about competition for mates. But the effects of estrogen on bone growth may be answer enough. Answers Hidden in Bone Human sexual size dimorphism, the difference in height between males and females, is often touted as a classic example of sexual selection: the kind of trait whose evolution was driven by differences in reproductive success rather than survival.

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Why are boys taller than girls

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Boys’ and girls’ height curves