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!
95% genes
I'd say more genes. I have 3 older brothers who are either 5'7" or 5'8 with a 5'8" dad all with a size 8 foot. We all ate the same food growing up. I'm 6'1" with size 14 shoes.
Kinda true me any my brother are close in height but he's still taller, he's 6'2 I hope I can reach his height though haha
Love this channel
It's both.
I haven't watched the video, but it's shown that regions that didn't have access to a good supply of food, once they started getting access to food the next generation of children sprung up. In the US people are more or less the height of their parents, but in like, Korea, it's normal for kids to be a foot taller than their parents. Same is happening in some parts of Mexico.
I'm on the shorter side of my family, so genes lol.