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Is Height Genetic?

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06:55   |   Sep 18, 2018

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Is Height Genetic?
Is Height Genetic? thumb Is Height Genetic? thumb Is Height Genetic? thumb

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  • Hey smart people, Joe here.
  • I am a descendent of giants.
  • With a grandfather, dad, two uncles, and an aunt all towering over 6 feet tall.
  • We are the people you don’t want to stand behind at a Bon Jovi concert, but we’re
  • also the people who can get that thing off the top shelf for you.
  • At 6’3”, I turned out to be the short one in the family.
  • Now that I have a son myself, I’m wondering if he’s going to be tall too.
  • Is height only written in our genes or is there something else that determines how tall
  • we get?
  • [OPEN]
  • These days, the average American woman is about five foot four, while the average Joe
  • American male is about five foot nine.
  • But… human height has had its ups and downs over the centuries.
  • Three million years ago, our ancestor Australopithecus only stood about four feet tall.
  • One-and-a-half million years later , Homo erectus, the first early human to use complex
  • tools, reached up to five foot seven.
  • And by the Stone Age, men of the Gravettian hunter-gatherer culture in Europe stood at
  • an average of 6 feet.
  • Most of the historical data we have is for male height, because… reasons.
  • Then agriculture happened.
  • When Europeans switched to a lower-protein, higher-grain diet, men gradually lost 8 inches
  • in height, on average.
  • And they stayed that way for thousands of years.
  • By the time the 18th century rolled around, the average European man was only five foot
  • five inches tall.
  • But when those Europeans emigrated to America, their kids grew up to be five foot eight inches
  • tall on average.
  • A huge jump in just a generation.
  • During the Industrial Revolution heights took a dip due to urban crowding and disease, but
  • soon after, the human height boom continued and continues today.
  • Every decade for the past couple centuries Europeans have grown an average of about half
  • an inch.
  • Today, Dutch men are the tallest people in the world, with an average height of just
  • over 6 feet - back to where those Gravettians started 8 millennia ago.
  • These fluctuations of height, sometimes within a single generation, show that our environment
  • determines a big part of how tall we are.
  • But people in different regions, and different families, show us that height has genetic
  • causes too.
  • So which has a bigger role, nature?
  • Or nurture?
  • In the early 19th century, scientists first noticed a correlation between people’s heights
  • and their wealth – people from poor backgrounds tended to be shorter than people who were
  • more well-off.
  • Instead of asking whether someone’s upbringing might influence their height, many scholars
  • at the time decided tallness was a physical mark of “superior” humans.
  • Francis Galton - who would later become infamous for popularizing eugenics - was the first
  • scientist to conduct a large-scale, systematic study of height.
  • He precisely measured the height of thousands of people as part of a sort of scientific
  • side show.
  • But Galton’s results were confusing.
  • Parents’ heights often didn’t predict the heights of their kids.
  • The heights of siblings on the other hand, were much closer.
  • This inspired scientists to look at height in twins.
  • Studying twins can teach us a ton about how genes and environments influence human attributes.
  • Fraternal twins can be as different genetically as any other pair of siblings, with the added
  • advantage of being exactly the same age.
  • Identical twins are genetically, well, identical.
  • So we can see how much genetic carbon copies end up differing.
  • And twins separated at birth offer a window into what happens when genetically identical
  • individuals grow up in very different environments.
  • Turns out that twins, especially identical twins, tend to be close in height - but not
  • exactly the same.
  • Twin studies, like history, show us genes can only be part of the story when it comes
  • to height.
  • So how big a part?
  • In 2007, scientists compared height and DNA between more than 11,000 pairs of siblings
  • and found that, across humans, 86% of height’s variation can be explained by genetics.
  • As traits go, this is very high; for comparison, genetics only explains about 26% of left-handedness.
  • So we should be able to predict a person’s height from his or her DNA right?
  • Not so fast.
  • We know genes make a huge difference, just not which genes.
  • So far, scientists have identified about 800 genes that influence height, but many of them
  • only make a tiny contribution.
  • Take HGMA2, one of the first genes linked to height.
  • Having one copy of the “tall” version only “lifts” a person about an eighth
  • of an inch, so even if you inherit a copy from both of your parents, that still only
  • gains you a quarter of an inch at most.
  • Altogether, the 800 height genes we know of can only explain 27% of how height varies
  • between people.
  • There’s clearly lots of genetic influence we don’t understand.
  • Maybe the effects of some genes add up in unexpected ways - genes may interact in combinations,
  • where four and four makes sixteen, not eight.
  • If we could just study the DNA of all the 7 billion people on Earth, maybe we would
  • find all the genes that affect height.
  • Or maybe we’d find that scientists have overestimated the contribution of genetics?
  • Because our environment, defined by health and diet, certainly has a hand in shaping
  • our height.
  • South Koreans today are more than an inch taller than North Koreans, despite minimal
  • genetic differences.
  • Clearly, one’s diet during childhood, is a crucial in determining adult height.
  • That’s why humans shrank with the switch to agriculture and again during the Industrial
  • Revolution.
  • Today, most scientists agree that nature and nurture combine to shape our height.
  • Some even propose calling height an “omnigenic” trait - one that nearly all our genes influence
  • in some way.
  • For now, the only surefire way to know how tall you’ll end up… is just to wait and see.
  • Stay curious!

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I’m tall. Most of the people in my family are tall. Does that mean my son will be tall? Turns out the inheritance of height is a lot more complicated than we thought. Scientists know that nature (genes) and nurture (environment) both play a role, but after more than a century of questions, we’re only just now starting to get some answers

REFERENCES:

Fryar, C.D. et al. (2016). Anthropometric reference data for
children and adults: United States, 2011–2014. National Center for Health
Statistics. Vital Health Stat 3(39).

NCD Risk Factor Collaboration. (2016). A century of trends in adult human height. eLife
5:e13410.

Visscher, P.M. et al. (2007). Genome partitioning of genetic variation for height from 11,214 sibling pairs. American Journal of Human Genetics 81:1104–10.

Zimmer, C. (2018). She has her mother’s laugh: The powers, perversions, and potential of heredity. New York: Dutton. http://bit.ly/2xi5H0M

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