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← How we're building the world's largest family tree

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Showing Revision 10 created 09/25/2019 by Brian Greene.

  1. People use the internet
    for various reasons.

  2. It turns out that one of the most
    popular categories of website
  3. is something that people
    typically consume in private.
  4. It involves curiosity,
  5. non-insignificant levels
    of self-indulgence
  6. and is centered around recording
    the reproductive activities
  7. of other people.
  8. (Laughter)
  9. Of course, I'm talking about genealogy --
  10. (Laughter)

  11. the study of family history.
  12. When it comes to detailing family history,

  13. in every family, we have this person
    that is obsessed with genealogy.
  14. Let's call him Uncle Bernie.
  15. Uncle Bernie is exactly the last person
    you want to sit next to
  16. in Thanksgiving dinner,
  17. because he will bore you to death
    with peculiar details
  18. about some ancient relatives.
  19. But as you know,
  20. there is a scientific side for everything,
  21. and we found that Uncle Bernie's stories
  22. have immense potential
    for biomedical research.
  23. We let Uncle Bernie
    and his fellow genealogists

  24. document their family trees through
    a genealogy website called geni.com.
  25. When users upload
    their trees to the website,
  26. it scans their relatives,
  27. and if it finds matches to existing trees,
  28. it merges the existing
    and the new tree together.
  29. The result is that large
    family trees are created,
  30. beyond the individual level
    of each genealogist.
  31. Now, by repeating this process
    with millions of people
  32. all over the world,
  33. we can crowdsource the construction
    of a family tree of all humankind.
  34. Using this website,

  35. we were able to connect 125 million people
  36. into a single family tree.
  37. I cannot draw the tree
    on the screens over here
  38. because they have less pixels
  39. than the number of people in this tree.
  40. But here is an example of a subset
    of 6,000 individuals.
  41. Each green node is a person.
  42. The red nodes represent marriages,
  43. and the connections represent parenthood.
  44. In the middle of this tree,
    you see the ancestors.
  45. And as we go to the periphery,
    you see the descendants.
  46. This tree has seven
    generations, approximately.
  47. Now, this is what happens
    when we increase the number of individuals

  48. to 70,000 people --
  49. still a tiny subset
    of all the data that we have.
  50. Despite that, you can already see
    the formation of gigantic family trees
  51. with many very distant relatives.
  52. Thanks to the hard work
    of our genealogists,

  53. we can go back in time
    hundreds of years ago.
  54. For example, here is Alexander Hamilton,
  55. who was born in 1755.
  56. Alexander was the first
    US Secretary of the Treasury,
  57. but mostly known today
    due to a popular Broadway musical.
  58. We found that Alexander has deeper
    connections in the showbiz industry.
  59. In fact, he's a blood relative of ...
  60. Kevin Bacon!
  61. (Laughter)

  62. Both of them are descendants
    of a lady from Scotland

  63. who lived in the 13th century.
  64. So you can say that Alexander Hamilton
  65. is 35 degrees of Kevin Bacon genealogy.
  66. (Laughter)

  67. And our tree has millions
    of stories like that.

  68. We invested significant efforts
    to validate the quality of our data.

  69. Using DNA, we found that .3 percent of
    the mother-child connections in our data
  70. are wrong,
  71. which could match the adoption rate
    in the US pre-Second World War.
  72. For the father's side,

  73. the news is not as good:
  74. 1.9 percent of the father-child
    connections in our data are wrong.
  75. And I see some people smirk over here.
  76. It is what you think --
  77. there are many milkmen out there.
  78. (Laughter)
  79. However, this 1.9 percent error rate
    in patrilineal connections
  80. is not unique to our data.
  81. Previous studies found
    a similar error rate
  82. using clinical-grade pedigrees.
  83. So the quality of our data is good,
  84. and that should not be a surprise.
  85. Our genealogists have
    a profound, vested interest
  86. in correctly documenting
    their family history.
  87. We can leverage this data to learn
    quantitative information about humanity,

  88. for example, questions about demography.
  89. Here is a look at all our profiles
    on the map of the world.
  90. Each pixel is a person
    that lived at some point.
  91. And since we have so much data,
  92. you can see the contours
    of many countries,
  93. especially in the Western world.
  94. In this clip, we stratified
    the map that I've showed you
  95. based on the year of births of individuals
    from 1400 to 1900,
  96. and we compared it
    to known migration events.
  97. The clip is going to show you
    that the deepest lineages in our data
  98. go all the way back to the UK,
  99. where they had better record keeping,
  100. and then they spread along
    the routes of Western colonialism.
  101. Let's watch this.
  102. (Music)
  103. [Year of birth: ]
  104. [1492 - Columbus sails the ocean blue]
  105. [1620 - Mayflower lands in Massachusetts]
  106. [1652 - Dutch settle in South Africa]
  107. [1788 - Great Britain penal
    transportation to Australia starts]
  108. [1836 - First migrants use Oregon Trail]
  109. [all activity]
  110. I love this movie.

  111. Now, since these migration events
    are giving the context of families,

  112. we can ask questions such as:
  113. What is the typical distance
    between the birth locations
  114. of husbands and wives?
  115. This distance plays
    a pivotal role in demography,
  116. because the patterns in which
    people migrate to form families
  117. determine how genes spread
    in geographical areas.
  118. We analyzed this distance using our data,
  119. and we found that in the old days,
  120. people had it easy.
  121. They just married someone
    in the village nearby.
  122. But the Industrial Revolution
    really complicated our love life.
  123. And today, with affordable flights
    and online social media,
  124. people typically migrate more than
    100 kilometers from their place of birth
  125. to find their soul mate.
  126. So now you might ask:

  127. OK, but who does the hard work
    of migrating from places to places
  128. to form families?
  129. Are these the males or the females?
  130. We used our data to address this question,
  131. and at least in the last 300 years,
  132. we found that the ladies do the hard work
  133. of migrating from places
    to places to form families.
  134. Now, these results
    are statistically significant,
  135. so you can take it as scientific fact
    that males are lazy.
  136. (Laughter)

  137. We can move from questions
    about demography

  138. and ask questions about human health.
  139. For example, we can ask
  140. to what extent genetic variations
    account for differences in life span
  141. between individuals.
  142. Previous studies analyzed the correlation
    of longevity between twins
  143. to address this question.
  144. They estimated that the genetic
    variations account for
  145. about a quarter of the differences
    in life span between individuals.
  146. But twins can be correlated
    due to so many reasons,
  147. including various environmental effects
  148. or a shared household.
  149. Large family trees give us the opportunity
    to analyze both close relatives,
  150. such as twins,
  151. all the way to distant relatives,
    even fourth cousins.
  152. This way we can build robust models
  153. that can tease apart the contribution
    of genetic variations
  154. from environmental factors.
  155. We conducted this analysis using our data,
  156. and we found that genetic variations
    explain only 15 percent
  157. of the differences in life span
    between individuals.
  158. That is five years, on average.
  159. So genes matter less than
    what we thought before to life span.
  160. And I find it great news,
  161. because it means that
    our actions can matter more.
  162. Smoking, for example, determines
    10 years of our life expectancy --
  163. twice as much as what genetics determines.
  164. We can even have more surprising findings

  165. as we move from family trees
  166. and we let our genealogists
    document and crowdsource DNA information.
  167. And the results can be amazing.
  168. It might be hard to imagine,
    but Uncle Bernie and his friends
  169. can create DNA forensic capabilities
  170. that even exceed
    what the FBI currently has.
  171. When you place the DNA
    on a large family tree,
  172. you effectively create a beacon
  173. that illuminates the hundreds
    of distant relatives
  174. that are all connected to the person
    that originated the DNA.
  175. By placing multiple beacons
    on a large family tree,
  176. you can now triangulate the DNA
    of an unknown person,
  177. the same way that the GPS system
    uses multiple satellites
  178. to find a location.
  179. The prime example
    of the power of this technique

  180. is capturing the Golden State Killer,
  181. one of the most notorious criminals
    in the history of the US.
  182. The FBI had been searching
    for this person for over 40 years.
  183. They had his DNA,
  184. but he never showed up
    in any police database.
  185. About a year ago, the FBI
    consulted a genetic genealogist,
  186. and she suggested that they submit
    his DNA to a genealogy service
  187. that can locate distant relatives.
  188. They did that,
  189. and they found a third cousin
    of the Golden State Killer.
  190. They built a large family tree,
  191. scanned the different
    branches of that tree,
  192. until they found a profile
    that exactly matched
  193. what they knew about
    the Golden State Killer.
  194. They obtained DNA from this person
    and found a perfect match
  195. to the DNA they had in hand.
  196. They arrested him
    and brought him to justice
  197. after all these years.
  198. Since then, genetic genealogists
    have started working with
  199. local US law enforcement agencies
  200. to use this technique
    in order to capture criminals.
  201. And only in the past six months,
  202. they were able to solve
    over 20 cold cases with this technique.
  203. Luckily, we have people like Uncle
    Bernie and his fellow genealogists

  204. These are not amateurs
    with a self-serving hobby.
  205. These are citizen scientists
    with a deep passion to tell us who we are.
  206. And they know that the past
    can hold a key to the future.
  207. Thank you very much.

  208. (Applause)