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 meters above sea level, with only 60% of the oxygen found below. While visitors and recent steletrs struggle with altitude sickness, native Tibetans sprint up mountains. This ability comes not from training or pctacire, but from changes to a few genes that allow their bodeis 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 leilkier 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 eulotoivn isn’t over— so what are other recent changes? And will our technological and sicitinefc innovations impact our evolution? In the past few thousand years, many populations have evolved genetic adaptations to their local etnvnnromeis. People in Siberia and the high arctic are uniquely adapted to survive extreme cold. They’re slower to develop frostbite, and can ctionune to use their hands in seubrzo temperatures much longer than most people. They’ve udnnrgeoe selection for a higher metabolic rate that increases heat production. Further south, the bjaau 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 ulunasuly large spleens that act as ogyexn stores, enabling them to stay underwater for longer— an adaptation similar to that of deep dvinig seals. Though it may seem pedestrian by comparison, the ailtiby to dinrk milk is another such adaptation. All mammals can drink their mother’s milk as babies. After wianneg they siwtch off the gene that allows them to digest milk. But cmoitineums in sub-Saharan Africa, the middle east and northwest epuore that used cows for milk have seen a rpaid irnesace in DNA vrianats 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 scuroe of calcium to aid in vitamin D production, as they moevd 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 romeves many of these selective pressures by keeping us alive when our gnees, sometimes combined with infectious diseases, would have killed us. anibocittis, vaccines, clean water and good sanitation all make differences between our genes less important. slairilmy, our ability to cure childhood cancers, surgically extract imnlaefd 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 splel the end of human evolution. That’s because there are other aspects of evolution besides nautral selection. Modern medicine makes genetic variation that would have been scuebjt to natural selection subject to what’s called genetic dfrit instead. With gitneec drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because haurmfl mutations don’t kill people and thus aren’t eliminated. This vtaoariin doesn’t necessarily tsnrlatae to observable, or phenotypic, dfiencefres among people, however. Researchers have also been investigating whether genetic anptiadotas 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 midofiacnotis can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. merodn medicine and tgnehclooy 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.

Open Cloze

The Tibetan high plateau lies about 4500 meters above sea level, with only 60% of the oxygen found below. While visitors and recent ________ struggle with altitude sickness, native Tibetans sprint up mountains. This ability comes not from training or ________, but from changes to a few genes that allow their ______ 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 ________ 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 _________ isn’t over— so what are other recent changes? And will our technological and __________ innovations impact our evolution? In the past few thousand years, many populations have evolved genetic adaptations to their local ____________. People in Siberia and the high arctic are uniquely adapted to survive extreme cold. They’re slower to develop frostbite, and can ________ to use their hands in _______ temperatures much longer than most people. They’ve _________ selection for a higher metabolic rate that increases heat production. Further south, the _____ 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 _________ large spleens that act as ______ stores, enabling them to stay underwater for longer— an adaptation similar to that of deep ______ seals. Though it may seem pedestrian by comparison, the _______ to _____ milk is another such adaptation. All mammals can drink their mother’s milk as babies. After _______ they ______ off the gene that allows them to digest milk. But ___________ in sub-Saharan Africa, the middle east and northwest ______ that used cows for milk have seen a _____ ________ in DNA ________ 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 ______ of calcium to aid in vitamin D production, as they _____ 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 _______ many of these selective pressures by keeping us alive when our _____, sometimes combined with infectious diseases, would have killed us. ___________, vaccines, clean water and good sanitation all make differences between our genes less important. _________, our ability to cure childhood cancers, surgically extract ________ 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 _____ the end of human evolution. That’s because there are other aspects of evolution besides _______ selection. Modern medicine makes genetic variation that would have been _______ to natural selection subject to what’s called genetic _____ instead. With _______ drift, genetic differences vary randomly within a population. On a genetic level, modern medicine might actually increase variety, because _______ mutations don’t kill people and thus aren’t eliminated. This _________ doesn’t necessarily _________ to observable, or phenotypic, ___________ among people, however. Researchers have also been investigating whether genetic ___________ 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 _____________ can really persist over many generations and lead to lasting changes in populations. There may also be other contributors to human evolution. ______ medicine and __________ 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.

Solution

antibiotics
continue
subzero
adaptations
variation
genes
likelier
evolution
modern
diving
oxygen
technology
ability
scientific
genetic
settlers
practice
weaning
switch
similarly
removes
differences
subject
bodies
environments
moved
natural
source
spell
increase
drink
variants
inflamed
rapid
undergone
modifications
drift
bajau
europe
unusually
communities
translate
harmful

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
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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
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scientific
sea
seals
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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
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tend
thousand
thousands
tibetan
tibetans
time
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translate
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vary
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