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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. Siblings and cousins, too.

  • 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?

  • These days, the average American woman is about 5'4", while the average Joe American male is about 5'9".

  • Buthuman height has had its ups and downs over the centuries.

  • Three million years ago, our ancestor Australopithecus only stood about 4' tall.

  • One-and-a-half million years later , Homo erectus, the first early human to use complex tools, reached up to 5'7".

  • 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 5'5" inches tall.

  • But when those Europeans emigrated to America, their kids grew up to be 5'8" 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 feetback to where those Gravettians started 8 millennia agoand, almost as tall as me.

  • 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 wealthpeople 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 Galtonwho would later become infamous for popularizing eugenicswas 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 heightbut 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 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?

  • Well, 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 HMGA2, one of the first genes linked to height.

  • Having one copy of thetallversion onlylifts” 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 waysgenes 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 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 anomnigenictraitone that nearly all our genes influence in some way.

  • For now, the only surefire way to know how tall you'll end upis just to wait and see.

  • Stay curious!

  • Hey guys, I want to take a second to tell you about "REINVENTORS". It's a new show from PBS Digital Studios and KCTS 9 in Seattle.

  • We'll introduce you to the scientists and tinkerers in the specific North West make cutting edge of green technology.

  • They'll try edible plastic, so you don't have to. And bring you to unexpected places like a garage in Seattle with a nuclear reactor in it.

  • You can check out REINVENTORS and subscribe to them at the link in the description.

Hey smart people, Joe here.

Subtitles and vocabulary

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B1 US height tall average identical genetic influence

Is Height All In Our Genes?

  • 1775 126
    Emily posted on 2019/01/11
Video vocabulary

Keywords

crucial

US /ˈkruʃəl/

UK /'kru:ʃl/

  • adjective
  • Extremely important or necessary
  • Extremely important or necessary; decisive or critical.
  • Difficult and very important
  • Of great importance to the success of something.
  • Extremely important or necessary; decisive.
  • Involving an extremely important decision or result.
trait

US /tret/

UK /treɪt/

  • noun
  • A particular characteristic that can produce a particular type of behavior
  • A distinguishing quality or characteristic, typically one belonging to a person.
  • A genetically determined characteristic or condition.
determine

US /dɪˈtɚmɪn/

UK /dɪ'tɜ:mɪn/

  • verb
  • Be a deciding factor in
  • To control exactly how something will be or act
  • To officially decide (something) especially because of evidence or facts; to control or influence directly; to find out or establish exactly, as a result of research or calculation.
  • To establish the facts about; discover
  • other
  • To cause (something) to occur in a particular way or to have a particular nature.
  • To officially decide (something) as the result of evidence or facts; to establish exactly, typically as a result of research or calculation.
  • To find out or establish precisely as a result of research or calculation.
  • To find out or establish exactly, usually as a result of research or calculation.
  • To be the deciding factor in; to control or influence directly.
  • other
  • To decide firmly on a course of action; to resolve.
average

US /ˈævərɪdʒ, ˈævrɪdʒ/

UK /'ævərɪdʒ/

  • noun
  • Total of numbers divided by the number of items
  • verb
  • To add numbers then divide by the number of items
  • adjective
  • Typical or normal; usual; ordinary
tend

US /tɛnd/

UK /tend/

  • verb
  • To move or act in a certain manner
  • To take care of
  • To regularly behave in a certain way
interact

US /ˌɪntɚˈækt/

UK /ˌɪntər'ækt/

  • verb
  • To talk or do things with each other
  • other
  • To communicate or work together.
identify

US /aɪˈdɛntəˌfaɪ/

UK /aɪ'dentɪfaɪ/

  • verb
  • To indicate who or what someone or something is
  • other
  • To discover or determine something.
  • To say exactly what something is
  • To recognize someone or something and be able to say who or what they are
  • other
  • To feel that you understand and share the feelings of someone else
  • To feel that you are similar to someone, and understand them or their situation because of this
measure

US /ˈmɛʒɚ/

UK /ˈmeʒə(r)/

  • noun
  • Plan to achieve a desired result
  • A plan or course of action taken to achieve a particular purpose.
  • A certain amount or degree of something.
  • A division of time in music, usually consisting of a fixed number of beats.
  • Tool used to calculate the size of something
  • A standard unit or system used for measuring.
  • other
  • To assess or estimate the extent, quantity, or effect of something.
  • To determine the size, amount, or degree of an object or substance by comparison with a standard unit.
  • verb
  • To determine the value or importance of something
  • To calculate size, weight or temperature of
  • other
  • To take actions to achieve a particular purpose.
environment

US /ɛnˈvaɪrənmənt, -ˈvaɪən-/

UK /ɪn'vaɪrənmənt/

  • noun
  • A set of hardware or software parameters that define the characteristics of a computer system.
  • The natural world, as a whole or in a particular geographical area, especially as affected by human activity.
  • Natural world in which plants and animals live
  • The people and things that are around you that affect how you behave and develop.
  • The entire surrounding conditions of something
influence

US / ˈɪnfluəns/

UK /'ɪnflʊəns/

  • noun
  • The power to affect what happens, to persuade etc.
  • A person or thing that affects someone or something in an important way.
  • verb
  • To affect or change something indirectly
  • other
  • To have an effect on the character, development, or behavior of someone or something.
  • To persuade someone to do something.
  • other
  • The ability to control or affect what happens
  • The power to have an effect on someone or something.