TedTest

From the Ted Talk by Laurence Hurst: Is human evolution speeding up or slowing down?

Unscramble the Blue Letters

The Tibetan high plateau lies about 4500 mtrees above sea level, with only 60% of the oxygen found below. While visitors and recent seerttls sgtlgure with altitude sickness, navite tbnaeits sprint up minoutans. This ability comes not from training or practice, but from changes to a few genes that allow their bodies to make the most of limited oxygen. These differences are apparent from birth— Tibetan babies have, on average, higher birth weights, higher oxygen saturation, and are much likelier to survive than other babies born in this environment. These genetic changes are ettamised to have evolved over the last 3,000 years or so, and are ongoing. That may sound like a long time, but would be the fastest an adaptation has ever evolved in a human population. It’s clear that human evolution isn’t over— so what are other recent changes? And will our tenlcihogacol and scientific innovations impact our evolution? In the past few thousand years, many populations have evolved genetic aoadttnpais to their local environments. People in Siberia and the high arctic are uiqlueny adapted to survive extreme cold. They’re slower to deelvop frostbite, and can cionnute to use their hands in subzero temperatures much longer than most people. They’ve undergone selection for a higher metabolic rate that increases heat production. Further south, the Bajau ppoele of southeast Asia can dive 70 meters and stay underwater for almost fifteen minutes. Over thousands of yares living as nomadic hunters at sea, they have genetically-hardwired uuuallnsy large spleens that act as oxgeyn stores, enabling them to stay utnerawder for longer— an adaptation similar to that of deep diving seals. Though it may seem pdterisaen by comparison, the ability to drink milk is another such adaptation. All maammls can drink their mother’s milk as babies. After weaning they switch off the gene that allows them to digest milk. But communities in sub-Saharan Africa, the middle east and northwest Europe that used cows for milk have seen a rpaid irnaesce in DNA variants that pnreevt the gene from shincitwg off over the last 7 to 8000 years. At least in eporue, milk dinkinrg may have given people a source of calcium to aid in vitamin D putocrdion, as they moevd north and sunlight, the usual source of vitamin D, decreased. Though not always in obuvois ways, all of these changes ipmvroe people’s cchnae of surviving to reproductive age— that’s what drives natural selection, the force behind all these eltivorunaoy changes. Modern medicine rmoeves many of these selective prurseses by keeping us alive when our genes, sometimes combined with infectious diseases, would have killed us. Antibiotics, vaccines, clean water and good sanitation all make differences between our genes less inproatmt. slamlriiy, our atbliiy to cure childhood cancers, surgically extract inflamed appendixes, and deliver babies whose mothers have life-threatening pregnancy-specific conditions, all tend to stop sceotelin by allowing more people to survive to a reproductive age. But even if every person on Earth has access to modern medicine, it won’t spell the end of hmaun evolution. That’s because there are other asetcps of evolution besides natural selection. Modern medicine makes genetic variation that would have been subject to natural selection subject to what’s called genetic drift instead. With giteenc drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because harmful mutations don’t kill people and thus aren’t eliminated. This variation doesn’t necessarily translate to observable, or pnthpoieyc, dneiffeercs among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through epigenetic modification: changes not to genes themselves, but to whether and when certain genes are esepxserd. These changes can happen during a lifetime, and may even be pssaed to offspring— but so far researchers are conflicted over whether epigenetic modifications can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. Modern medicine and technology are very new, even compared to the quickest, most recent changes by natural selection— so only time can tell how our present will shpae our future.

Open Cloze

The Tibetan high plateau lies about 4500 ______ above sea level, with only 60% of the oxygen found below. While visitors and recent ________ ________ with altitude sickness, ______ ________ sprint up _________. This ability comes not from training or practice, but from changes to a few genes that allow their bodies to make the most of limited oxygen. These differences are apparent from birth— Tibetan babies have, on average, higher birth weights, higher oxygen saturation, and are much likelier to survive than other babies born in this environment. These genetic changes are _________ to have evolved over the last 3,000 years or so, and are ongoing. That may sound like a long time, but would be the fastest an adaptation has ever evolved in a human population. It’s clear that human evolution isn’t over— so what are other recent changes? And will our _____________ and scientific innovations impact our evolution? In the past few thousand years, many populations have evolved genetic ___________ to their local environments. People in Siberia and the high arctic are ________ adapted to survive extreme cold. They’re slower to _______ frostbite, and can ________ to use their hands in subzero temperatures much longer than most people. They’ve undergone selection for a higher metabolic rate that increases heat production. Further south, the Bajau ______ of southeast Asia can dive 70 meters and stay underwater for almost fifteen minutes. Over thousands of _____ living as nomadic hunters at sea, they have genetically-hardwired _________ large spleens that act as ______ stores, enabling them to stay __________ for longer— an adaptation similar to that of deep diving seals. Though it may seem __________ by comparison, the ability to drink milk is another such adaptation. All _______ can drink their mother’s milk as babies. After weaning they switch off the gene that allows them to digest milk. But communities in sub-Saharan Africa, the middle east and northwest Europe that used cows for milk have seen a _____ ________ in DNA variants that _______ the gene from _________ off over the last 7 to 8000 years. At least in ______, milk ________ may have given people a source of calcium to aid in vitamin D __________, as they _____ north and sunlight, the usual source of vitamin D, decreased. Though not always in _______ ways, all of these changes _______ people’s ______ of surviving to reproductive age— that’s what drives natural selection, the force behind all these ____________ changes. Modern medicine _______ many of these selective _________ by keeping us alive when our genes, sometimes combined with infectious diseases, would have killed us. Antibiotics, vaccines, clean water and good sanitation all make differences between our genes less _________. _________, our _______ to cure childhood cancers, surgically extract inflamed appendixes, and deliver babies whose mothers have life-threatening pregnancy-specific conditions, all tend to stop _________ by allowing more people to survive to a reproductive age. But even if every person on Earth has access to modern medicine, it won’t spell the end of _____ evolution. That’s because there are other _______ of evolution besides natural selection. Modern medicine makes genetic variation that would have been subject to natural selection subject to what’s called genetic drift instead. With _______ drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because harmful mutations don’t kill people and thus aren’t eliminated. This variation doesn’t necessarily translate to observable, or __________, ___________ among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through epigenetic modification: changes not to genes themselves, but to whether and when certain genes are _________. These changes can happen during a lifetime, and may even be ______ to offspring— but so far researchers are conflicted over whether epigenetic modifications can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. Modern medicine and technology are very new, even compared to the quickest, most recent changes by natural selection— so only time can tell how our present will _____ our future.

Solution

aspects
pedestrian
pressures
underwater
oxygen
meters
people
differences
moved
rapid
mountains
human
removes
shape
ability
drinking
struggle
prevent
switching
tibetans
chance
increase
phenotypic
production
continue
settlers
improve
uniquely
expressed
obvious
years
unusually
selection
technological
passed
important
adaptations
mammals
europe
evolutionary
estimated
genetic
native
develop
similarly

Original Text

The Tibetan high plateau lies about 4500 meters above sea level, with only 60% of the oxygen found below. While visitors and recent settlers struggle with altitude sickness, native Tibetans sprint up mountains. This ability comes not from training or practice, but from changes to a few genes that allow their bodies to make the most of limited oxygen. These differences are apparent from birth— Tibetan babies have, on average, higher birth weights, higher oxygen saturation, and are much likelier to survive than other babies born in this environment. These genetic changes are estimated to have evolved over the last 3,000 years or so, and are ongoing. That may sound like a long time, but would be the fastest an adaptation has ever evolved in a human population. It’s clear that human evolution isn’t over— so what are other recent changes? And will our technological and scientific innovations impact our evolution? In the past few thousand years, many populations have evolved genetic adaptations to their local environments. People in Siberia and the high arctic are uniquely adapted to survive extreme cold. They’re slower to develop frostbite, and can continue to use their hands in subzero temperatures much longer than most people. They’ve undergone selection for a higher metabolic rate that increases heat production. Further south, the Bajau people of southeast Asia can dive 70 meters and stay underwater for almost fifteen minutes. Over thousands of years living as nomadic hunters at sea, they have genetically-hardwired unusually large spleens that act as oxygen stores, enabling them to stay underwater for longer— an adaptation similar to that of deep diving seals. Though it may seem pedestrian by comparison, the ability to drink milk is another such adaptation. All mammals can drink their mother’s milk as babies. After weaning they switch off the gene that allows them to digest milk. But communities in sub-Saharan Africa, the middle east and northwest Europe that used cows for milk have seen a rapid increase in DNA variants that prevent the gene from switching off over the last 7 to 8000 years. At least in Europe, milk drinking may have given people a source of calcium to aid in vitamin D production, as they moved north and sunlight, the usual source of vitamin D, decreased. Though not always in obvious ways, all of these changes improve people’s chance of surviving to reproductive age— that’s what drives natural selection, the force behind all these evolutionary changes. Modern medicine removes many of these selective pressures by keeping us alive when our genes, sometimes combined with infectious diseases, would have killed us. Antibiotics, vaccines, clean water and good sanitation all make differences between our genes less important. Similarly, our ability to cure childhood cancers, surgically extract inflamed appendixes, and deliver babies whose mothers have life-threatening pregnancy-specific conditions, all tend to stop selection by allowing more people to survive to a reproductive age. But even if every person on Earth has access to modern medicine, it won’t spell the end of human evolution. That’s because there are other aspects of evolution besides natural selection. Modern medicine makes genetic variation that would have been subject to natural selection subject to what’s called genetic drift instead. With genetic drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because harmful mutations don’t kill people and thus aren’t eliminated. This variation doesn’t necessarily translate to observable, or phenotypic, differences among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through epigenetic modification: changes not to genes themselves, but to whether and when certain genes are expressed. These changes can happen during a lifetime, and may even be passed to offspring— but so far researchers are conflicted over whether epigenetic modifications can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. Modern medicine and technology are very new, even compared to the quickest, most recent changes by natural selection— so only time can tell how our present will shape our future.

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
modern medicine	4
human evolution	3
genetic adaptations	2
stay underwater	2
natural selection	2

Important Words

ability
access
act
adaptation
adaptations
adapted
africa
age
aid
alive
allowing
altitude
antibiotics
apparent
appendixes
arctic
asia
aspects
average
babies
bajau
birth
bodies
born
calcium
called
cancers
chance
childhood
clean
clear
cold
combined
communities
compared
comparison
conditions
conflicted
continue
contributors
cows
cure
decreased
deep
deliver
develop
differences
digest
diseases
dive
diving
dna
drift
drink
drinking
drives
earth
east
eliminated
enabling
environment
environments
epigenetic
estimated
europe
evolution
evolutionary
evolved
expressed
extract
extreme
fastest
fifteen
force
frostbite
future
gene
generations
genes
genetic
good
hands
happen
harmful
heat
high
higher
human
hunters
impact
important
improve
increase
increases
infectious
inflamed
innovations
investigating
keeping
kill
killed
large
lasting
lead
level
lies
lifetime
likelier
limited
living
local
long
longer
mammals
medicine
metabolic
meters
middle
milk
minutes
modern
modifications
mothers
mountains
moved
mutations
native
natural
necessarily
nomadic
north
northwest
observable
obvious
ongoing
oxygen
passed
pedestrian
people
persist
person
phenotypic
plateau
population
populations
practice
present
pressures
prevent
production
quickest
quickly
randomly
rapid
rate
removes
reproductive
researchers
sanitation
saturation
scientific
sea
seals
selection
selective
settlers
shape
siberia
sickness
similar
similarly
slower
sound
source
south
southeast
specific
spell
spleens
sprint
stay
stop
stores
struggle
subject
subzero
sunlight
surgically
survive
surviving
switch
switching
technological
technology
temperatures
tend
thousand
thousands
tibetan
tibetans
time
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translate
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usual
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