full transcript

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

Unscramble the Blue Letters

The Tibetan high pleatau lies about 4500 meters above sea level, with only 60% of the oyexgn found below. While visitors and recent settlers struggle with ailudtte 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 liitmed oxygen. These differences are apparent from birth— Tibetan babies have, on average, higher btirh weights, higher oxygen sauioarttn, 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 atiapaodtn 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 emrnivonents. People in Siberia and the high arctic are uniquely adapted to svivrue extreme cold. They’re slower to develop frostbite, and can continue to use their hands in subzero temperatures much longer than most pelpoe. 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 tuondashs of yares living as nomadic hunters at sea, they have genetically-hardwired uunlulsay large seelnps that act as oxygen stores, elbainng 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 wnniaeg they switch off the gene that allows them to digest milk. But communities in sub-Saharan acfira, the mddile east and northwest eroupe that used cows for milk have seen a rapid isencare 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 cilacum to aid in viiamtn D produioctn, 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 canhce of svinirvug to reproductive age— that’s what drives natural selection, the force behind all these evolutionary changes. Modern mdiience revmoes many of these selective pressures by kienepg us avlie when our genes, sometimes combined with infectious diseases, would have killed us. ationicibts, vaccines, clean water and good sanitation all make differences between our genes less important. Similarly, our ability to cure childhood canrecs, surgically extract inflamed appendixes, and deliver bibaes whose mothers have life-threatening pregnancy-specific conditions, all tend to stop scliteoen by anlwloig more people to survive to a reproductive age. But even if every poesrn on Earth has access to modern medicine, it won’t spell the end of human evolution. That’s because there are other aspects of eoutiovln besides nraautl 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, geteinc differences vary rodamlny within a population. On a genetic level, modern medicine might actually increase variety, because harmful mutations don’t kill people and thus aren’t emeiniltad. This variation doesn’t necessarily translate to olbbsverae, or phenotypic, differences among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through eigiteepnc modification: changes not to genes themselves, but to whether and when certain geens are expressed. These changes can happen during a lifetime, and may even be pessad to offspring— but so far researchers are conflicted over whether epigenetic modifications can really persist over many generations and lead to lntasig 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 sphae our future.

Open Cloze

The Tibetan high _______ lies about 4500 meters above sea level, with only 60% of the ______ found below. While visitors and recent settlers struggle with ________ 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 _______ oxygen. These differences are apparent from birth— Tibetan babies have, on average, higher _____ weights, higher oxygen __________, 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 __________ 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 ____________. People in Siberia and the high arctic are uniquely adapted to _______ extreme cold. They’re slower to develop frostbite, and can continue to use their hands in subzero temperatures much longer than most ______. 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 _________ of _____ living as nomadic hunters at sea, they have genetically-hardwired _________ large _______ that act as oxygen stores, ________ 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 _______ they switch off the gene that allows them to digest milk. But communities in sub-Saharan ______, the ______ east and northwest ______ that used cows for milk have seen a rapid ________ 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 _______ to aid in _______ D __________, 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 ______ of _________ to reproductive age— that’s what drives natural selection, the force behind all these evolutionary changes. Modern ________ _______ many of these selective pressures by _______ us _____ when our genes, sometimes combined with infectious diseases, would have killed us. ___________, vaccines, clean water and good sanitation all make differences between our genes less important. Similarly, our ability to cure childhood _______, surgically extract inflamed appendixes, and deliver ______ whose mothers have life-threatening pregnancy-specific conditions, all tend to stop _________ by ________ more people to survive to a reproductive age. But even if every ______ on Earth has access to modern medicine, it won’t spell the end of human evolution. That’s because there are other aspects of _________ besides _______ 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, _______ differences vary ________ within a population. On a genetic level, modern medicine might actually increase variety, because harmful mutations don’t kill people and thus aren’t __________. This variation doesn’t necessarily translate to __________, or phenotypic, differences among people, however. Researchers have also been investigating whether genetic adaptations to a specific environment could appear very quickly through __________ modification: changes not to genes themselves, but to whether and when certain _____ are expressed. 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 _______ 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

  1. lasting
  2. saturation
  3. genes
  4. increase
  5. calcium
  6. chance
  7. surviving
  8. person
  9. shape
  10. europe
  11. epigenetic
  12. limited
  13. antibiotics
  14. environments
  15. evolution
  16. cancers
  17. survive
  18. eliminated
  19. oxygen
  20. production
  21. plateau
  22. thousands
  23. selection
  24. keeping
  25. alive
  26. spleens
  27. genetic
  28. randomly
  29. removes
  30. medicine
  31. unusually
  32. years
  33. altitude
  34. people
  35. natural
  36. weaning
  37. babies
  38. africa
  39. birth
  40. enabling
  41. middle
  42. allowing
  43. observable
  44. vitamin
  45. passed
  46. adaptation

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

  1. ability
  2. access
  3. act
  4. adaptation
  5. adaptations
  6. adapted
  7. africa
  8. age
  9. aid
  10. alive
  11. allowing
  12. altitude
  13. antibiotics
  14. apparent
  15. appendixes
  16. arctic
  17. asia
  18. aspects
  19. average
  20. babies
  21. bajau
  22. birth
  23. bodies
  24. born
  25. calcium
  26. called
  27. cancers
  28. chance
  29. childhood
  30. clean
  31. clear
  32. cold
  33. combined
  34. communities
  35. compared
  36. comparison
  37. conditions
  38. conflicted
  39. continue
  40. contributors
  41. cows
  42. cure
  43. decreased
  44. deep
  45. deliver
  46. develop
  47. differences
  48. digest
  49. diseases
  50. dive
  51. diving
  52. dna
  53. drift
  54. drink
  55. drinking
  56. drives
  57. earth
  58. east
  59. eliminated
  60. enabling
  61. environment
  62. environments
  63. epigenetic
  64. estimated
  65. europe
  66. evolution
  67. evolutionary
  68. evolved
  69. expressed
  70. extract
  71. extreme
  72. fastest
  73. fifteen
  74. force
  75. frostbite
  76. future
  77. gene
  78. generations
  79. genes
  80. genetic
  81. good
  82. hands
  83. happen
  84. harmful
  85. heat
  86. high
  87. higher
  88. human
  89. hunters
  90. impact
  91. important
  92. improve
  93. increase
  94. increases
  95. infectious
  96. inflamed
  97. innovations
  98. investigating
  99. keeping
  100. kill
  101. killed
  102. large
  103. lasting
  104. lead
  105. level
  106. lies
  107. lifetime
  108. likelier
  109. limited
  110. living
  111. local
  112. long
  113. longer
  114. mammals
  115. medicine
  116. metabolic
  117. meters
  118. middle
  119. milk
  120. minutes
  121. modern
  122. modifications
  123. mothers
  124. mountains
  125. moved
  126. mutations
  127. native
  128. natural
  129. necessarily
  130. nomadic
  131. north
  132. northwest
  133. observable
  134. obvious
  135. ongoing
  136. oxygen
  137. passed
  138. pedestrian
  139. people
  140. persist
  141. person
  142. phenotypic
  143. plateau
  144. population
  145. populations
  146. practice
  147. present
  148. pressures
  149. prevent
  150. production
  151. quickest
  152. quickly
  153. randomly
  154. rapid
  155. rate
  156. removes
  157. reproductive
  158. researchers
  159. sanitation
  160. saturation
  161. scientific
  162. sea
  163. seals
  164. selection
  165. selective
  166. settlers
  167. shape
  168. siberia
  169. sickness
  170. similar
  171. similarly
  172. slower
  173. sound
  174. source
  175. south
  176. southeast
  177. specific
  178. spell
  179. spleens
  180. sprint
  181. stay
  182. stop
  183. stores
  184. struggle
  185. subject
  186. subzero
  187. sunlight
  188. surgically
  189. survive
  190. surviving
  191. switch
  192. switching
  193. technological
  194. technology
  195. temperatures
  196. tend
  197. thousand
  198. thousands
  199. tibetan
  200. tibetans
  201. time
  202. training
  203. translate
  204. undergone
  205. underwater
  206. uniquely
  207. unusually
  208. usual
  209. vaccines
  210. variants
  211. variation
  212. variety
  213. vary
  214. visitors
  215. vitamin
  216. water
  217. ways
  218. weaning
  219. weights
  220. years