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← How animals, bugs and plants are evolving in cities

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Showing Revision 5 created 08/24/2020 by Erin Gregory.

  1. This is where I grew up.
  2. A small village near the city of Rotterdam
  3. in the Netherlands.
  4. In the 1970s and 1980s,
    when I was a teenager,
  5. this area was still a quiet place.
  6. It was full of farms and fields
    and swampland,
  7. and I spent my free time there,
    enjoying myself,
  8. painting oil paintings like this one,
  9. collecting wildflowers, bird-watching
  10. and also collecting insects.
  11. And this was one of my prized finds.

  12. This is a very special beetle,
  13. an amazing beetle called an ant beetle.
  14. And this is a kind of beetle
    that lives its entire life
  15. inside an ant's nest.
  16. It has evolved to speak ant.
  17. It's using the same chemical signals,
  18. the same smells as the ants do,
    for communicating,
  19. and right now, this beetle
    is telling this worker ant,
  20. "Hey, I'm also a worker ant,
  21. I'm hungry, please feed me."
  22. And the ant complies,
  23. because the beetle is using
    the same chemicals.
  24. Over these millions of years,
  25. this beetle has evolved a way
    to live inside an ant society.
  26. Over the years,

  27. when I was living in that village,
  28. I collected 20,000 different beetles,
  29. and I built a collection
    of pinned beetles.
  30. And this got me interested,
    at a very early age, in evolution.
  31. How do all those different forms,
    how does all this diversity come about?
  32. So I became an evolutionary biologist,

  33. like Charles Darwin.
  34. And like Charles Darwin,
    I also soon became frustrated
  35. by the fact that evolution is something
    that happened mostly in the past.
  36. We study the patterns that we see today,
  37. trying to understand the evolution
    that took place in the past,
  38. but we can never actually see it
    taking place in real time.
  39. We cannot observe it.
  40. As Darwin himself already said,
  41. "We see nothing of these slow
    changes in progress,
  42. until the hand of time
    has marked the lapse of ages."
  43. Or do we?
  44. Over the past few decades,

  45. evolutionary biologists
    have come to realize that sometimes,
  46. evolution proceeds much faster
    and it can actually be observed,
  47. especially when the environment
    changes drastically
  48. and the need to adapt is great.
  49. And of course, these days,
  50. great environmental changes
    are usually caused by us.
  51. We mow, we irrigate, we plow, we build,
  52. we pump greenhouse gases
    into the atmosphere
  53. that change the climate.
  54. We release exotic plants and animals
  55. in places where they didn't live before,
  56. and we harvest fish and trees and game
    for our food and other needs.
  57. And all these environmental changes
    reach their epicenter in cities.

  58. Cities form a completely new habitat
    that we have created.
  59. And we clothe it in brick and concrete
    and glass and steel,
  60. which are impervious surfaces
  61. that plants can only root in
    with the greatest difficulty.
  62. Also in cities, we find
    the greatest concentrations

  63. of chemical pollution,
  64. of artificial light and noise.
  65. And we find wild mixtures
    of plants and animals
  66. from all over the world
    that live in the city,
  67. because they have escaped
    from the gardening
  68. and aquarium and pet trade.
  69. And what does a species do

  70. when it lives in a completely
    changed environment?
  71. Well, many, of course, go, sadly, extinct.
  72. But the ones that don't go extinct,
  73. they adapt in spectacular ways.
  74. Biologists these days
    are beginning to realize
  75. that cities are today's
    pressure cookers of evolution.
  76. These are places
    where wild animals and plants
  77. are evolving under our eyes very rapidly
  78. to suit these new, urban conditions.
  79. Exactly like the ant beetle did
    millions of years ago,
  80. when it moved inside an ant colony.
  81. We now find animals and plants
    that have moved inside the human colony
  82. and are adapting to our cities.
  83. And in doing so,
  84. we're also beginning to realize
  85. that evolution can actually
    proceed very fast.
  86. It does not always take
    the long lapse of ages;
  87. it can happen under our very eyes.
  88. This, for example,
    is the white-footed mouse.

  89. This is a native mammal
    from the area around New York,
  90. and more than 400 years ago,
    before the city was built,
  91. this mouse lived everywhere.
  92. But these days, they are stuck
    in little islands of green,
  93. the city's parks, surrounded by a sea
    of tarmac and traffic.
  94. A bit like a modern-day version
    of Darwin's finches on the Galapagos.
  95. And like Darwin's finches,

  96. the mice in each separate park
    have started evolving,
  97. have started to become
    different from each other.
  98. And this is my colleague,
    Jason Munshi-South,
  99. from Fordham University,
  100. who is studying this process.
  101. He is studying the DNA
    of the white-footed mice
  102. in New York City's parks,
  103. and trying to understand
    how they are beginning to evolve
  104. in that archipelago of islands.
  105. And he's using a kind of
    DNA fingerprinting, and he says,
  106. "If somebody gives me a mouse,
  107. doesn't tell me where it's from,
  108. just by looking at its DNA,
  109. I can tell exactly
    from which park it comes."
  110. That's how different they have become.
  111. And Jason has also discovered
    that those changes,

  112. these evolutionary changes,
  113. are not random, they mean something.
  114. For example, in Central Park,
  115. we find that the mice have evolved genes
  116. that allow them to deal
    with very fatty food.
  117. Human food.
  118. Twenty-five million people
    visit Central Park each year.
  119. It's the most heavily visited park
    in North America.
  120. And those people leave behind snack food
  121. and peanuts and junk food,
  122. and the mice have started feeding on that,
  123. and it's a completely different diet
    than what they're used to,
  124. and over the years,
  125. they have evolved to suit
    this very fatty, very human diet.
  126. And this is another city slicker animal.

  127. This is the European garden snail.
  128. A very common snail,
  129. it comes in all kinds of color variations,
  130. ranging from pale yellow to dark brown.
  131. And those colors are completely determined
  132. by the snail's DNA.
  133. And those colors also determine
    the heat management of the snail
  134. that lives inside that shell.
  135. For example, a snail
    that sits in the sunlight,
  136. in the bright sun,
  137. if it has a pale yellow shell,
  138. it doesn't heat up as much as a snail
    that sits inside a dark brown shell.
  139. Just like when you're sitting
    in a white car, you stay cooler
  140. than when you're sitting
    inside a black car.
  141. Now there is a phenomenon called
    the urban heat islands,

  142. which means that in the center
    of a big city,
  143. the temperature can be
    several degrees higher
  144. than outside of the big city.
  145. That has to do with the fact
  146. that you have these concentrations
    of millions of people,
  147. and all their activities
    and their machineries,
  148. they generate heat.
  149. Also, the wind is blocked
    by the tall buildings,
  150. and all the steel and brick
    and concrete absorb the solar heat
  151. and they radiate it out at night.
  152. So you get this bubble of hot air
    in the center of a big city,
  153. and my students and I figured
    that maybe those garden snails,
  154. with their variable shells,
  155. are adapting to the urban heat islands.
  156. Maybe in the center of a city,
  157. we find that the shell color is evolving
  158. in a direction to reduce
    overheating of the snails.
  159. And to study this, we started
    a citizen-science project.

  160. We built a free smartphone app,
  161. which allowed people
    all over the Netherlands
  162. to take pictures of snails
    in their garden, in their street,
  163. also in the countryside,
  164. and upload them to a citizen
    science web platform.
  165. And over a year, we got 10,000 pictures
  166. of snails that had been photographed
    in the Netherlands,
  167. and when we started analyzing the results,
  168. we found that indeed,
    our suspicions were confirmed.
  169. In the center of the urban heat islands,
  170. we find that the snails have evolved
    more yellow, more lighter-colored shells.
  171. Now the city snail and the Manhattan mouse

  172. are just two examples
    of a growing list of animals and plants
  173. that have evolved to suit
    this new habitat,
  174. this city habitat that we have created.
  175. And in a book that I've written
    about this subject,
  176. the subject of urban evolution,
  177. I give many more examples.
  178. For example, weeds that have evolved seeds
  179. that are better at germinating
    on the pavement.
  180. Grasshoppers that have evolved a song
  181. that has a higher pitch
    when they live close to noisy traffic.
  182. Mosquitoes that have evolved
    to feed on the blood of human commuters
  183. inside metro stations.
  184. And even the common city pigeon
  185. that has evolved ways to detox themselves
  186. from heavy-metal pollution
    by putting it in their feathers.
  187. Biologists like myself,
    all over the world,

  188. are becoming interested
    in this fascinating process
  189. of urban evolution.
  190. We are realizing that we're really
    at a unique event
  191. in the history of life on earth.
  192. A completely new ecosystem
  193. that is evolving and adapting
    to a habitat that we have created.
  194. And not just academics --

  195. we're also beginning to enlist
    the millions of pairs of hands
  196. and ears and eyes
    that are present in the city.
  197. Citizen scientists, schoolchildren --
  198. together with them,
  199. we are building
    a global observation network
  200. which allows us to watch this process
    of urban evolution taking place
  201. in real time.
  202. And at the same time,
    this also makes it clear to people
  203. that evolution is not
    just some abstract thing
  204. that you need to travel
    to the Galapagos to study,
  205. or that you need to be a paleontologist
    to understand what it is.
  206. It's a very ordinary biological process
  207. that's taking place
    all the time, everywhere.
  208. In your backyard,
    in the street where you live,
  209. right outside of this theater.
  210. But there is, of course,
    a flip side to my enthusiasm.

  211. When I go back to the village
    where I grew up,
  212. I no longer find those fields and swamps
    that I knew from my youth.
  213. The village has now been absorbed
  214. by the growing
    conglomeration of Rotterdam,
  215. and instead, I find shopping malls
  216. and I find suburbs and bus lanes.
  217. And many of the animals and plants
    that I was so accustomed to
  218. have disappeared,
    including perhaps that ant beetle.
  219. But I take comfort in the fact
    that the children growing up

  220. in that village today
  221. may no longer be experiencing
    that traditional nature
  222. that I grew up with,
  223. but they're surrounded
    by a new type of nature,
  224. a new type of ecosystem,
  225. that, to them, might be just as exciting
    as the old type was to me.
  226. They are living in a new,
    modern-day Galapagos.
  227. And by teaming up with citizen scientists
  228. and with evolutionary
    biologists like myself,
  229. they might become the Darwins
    of the 21st century,
  230. studying urban evolution.
  231. Thank you.

  232. (Applause)