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    "segs": [ {
      "utf8": "If you know an older left-handed person,"
    } ]
  }, {
    "tStartMs": 9301,
    "dDurationMs": 4802,
    "segs": [ {
      "utf8": "chances are they had to learn to write\nor eat with their right hand."
    } ]
  }, {
    "tStartMs": 14103,
    "dDurationMs": 1532,
    "segs": [ {
      "utf8": "And in many parts of the world,"
    } ]
  }, {
    "tStartMs": 15635,
    "dDurationMs": 4401,
    "segs": [ {
      "utf8": "it's still common practice to force\nchildren to use their \"proper\" hand."
    } ]
  }, {
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    "dDurationMs": 3763,
    "segs": [ {
      "utf8": "Even the word for right\nalso means correct or good,"
    } ]
  }, {
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    "dDurationMs": 3179,
    "segs": [ {
      "utf8": "not just in English,\nbut many other languages, too."
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    "segs": [ {
      "utf8": "But if being left-handed is so wrong,"
    } ]
  }, {
    "tStartMs": 30838,
    "dDurationMs": 2124,
    "segs": [ {
      "utf8": "then why does it happen\nin the first place?"
    } ]
  }, {
    "tStartMs": 33499,
    "dDurationMs": 4119,
    "segs": [ {
      "utf8": "Today, about 1/10 of the world's\npopulation are left-handed."
    } ]
  }, {
    "tStartMs": 37618,
    "dDurationMs": 2509,
    "segs": [ {
      "utf8": "Archeological evidence shows\nthat it's been that way"
    } ]
  }, {
    "tStartMs": 40127,
    "dDurationMs": 3273,
    "segs": [ {
      "utf8": "for as long as 500,000 years,"
    } ]
  }, {
    "tStartMs": 43400,
    "dDurationMs": 1816,
    "segs": [ {
      "utf8": "with about 10% of human remains"
    } ]
  }, {
    "tStartMs": 45216,
    "dDurationMs": 4709,
    "segs": [ {
      "utf8": "showing the associated differences\nin arm length and bone density,"
    } ]
  }, {
    "tStartMs": 49925,
    "dDurationMs": 4617,
    "segs": [ {
      "utf8": "and some ancient tools and artifacts\nshowing evidence of left-hand use."
    } ]
  }, {
    "tStartMs": 55099,
    "dDurationMs": 4397,
    "segs": [ {
      "utf8": "And despite what many may think,\nhandedness is not a choice."
    } ]
  }, {
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    "dDurationMs": 4679,
    "segs": [ {
      "utf8": "It can be predicted even before birth\nbased on the fetus' position in the womb."
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  }, {
    "tStartMs": 64861,
    "dDurationMs": 3488,
    "segs": [ {
      "utf8": "So, if handedness is inborn,\ndoes that mean it's genetic?"
    } ]
  }, {
    "tStartMs": 68823,
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    "segs": [ {
      "utf8": "Well, yes and no."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Identical twins, who have the same genes,\ncan have different dominant hands."
    } ]
  }, {
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    "segs": [ {
      "utf8": "In fact, this happens as often as it does\nwith any other sibling pair."
    } ]
  }, {
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    "segs": [ {
      "utf8": "But the chances of being\nright or left-handed"
    } ]
  }, {
    "tStartMs": 82689,
    "dDurationMs": 3121,
    "segs": [ {
      "utf8": "are determined by the handedness\nof your parents"
    } ]
  }, {
    "tStartMs": 85810,
    "dDurationMs": 2829,
    "segs": [ {
      "utf8": "in surprisingly consistent ratios."
    } ]
  }, {
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    "dDurationMs": 3308,
    "segs": [ {
      "utf8": "If your father was left-handed\nbut your mother was right-handed,"
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  }, {
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    "dDurationMs": 4116,
    "segs": [ {
      "utf8": "you have a 17% chance\nof being born left-handed,"
    } ]
  }, {
    "tStartMs": 96063,
    "dDurationMs": 3706,
    "segs": [ {
      "utf8": "while two righties will have\na left-handed child only 10% of the time."
    } ]
  }, {
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    "segs": [ {
      "utf8": "Handedness seems to be determined\nby a roll of the dice,"
    } ]
  }, {
    "tStartMs": 103702,
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    "segs": [ {
      "utf8": "but the odds are set by your genes."
    } ]
  }, {
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    "segs": [ {
      "utf8": "All of this implies there's a reason"
    } ]
  }, {
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    "segs": [ {
      "utf8": "that evolution has produced\nthis small proportion of lefties,"
    } ]
  }, {
    "tStartMs": 111582,
    "dDurationMs": 2239,
    "segs": [ {
      "utf8": "and maintained it\nover the course of millennia."
    } ]
  }, {
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    "segs": [ {
      "utf8": "And while there have been several theories"
    } ]
  }, {
    "tStartMs": 116304,
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    "segs": [ {
      "utf8": "attempting to explain why handedness\nexists in the first place,"
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  }, {
    "tStartMs": 119830,
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    "segs": [ {
      "utf8": "or why most people are right-handed,"
    } ]
  }, {
    "tStartMs": 121928,
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    "segs": [ {
      "utf8": "a recent mathematical model"
    } ]
  }, {
    "tStartMs": 123434,
    "dDurationMs": 3465,
    "segs": [ {
      "utf8": "suggests that the actual ratio\nreflects a balance"
    } ]
  }, {
    "tStartMs": 126899,
    "dDurationMs": 4282,
    "segs": [ {
      "utf8": "between competitive and cooperative\npressures on human evolution."
    } ]
  }, {
    "tStartMs": 131697,
    "dDurationMs": 1792,
    "segs": [ {
      "utf8": "The benefits of being left-handed"
    } ]
  }, {
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    "dDurationMs": 3920,
    "segs": [ {
      "utf8": "are clearest in activities\ninvolving an opponent,"
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  }, {
    "tStartMs": 137409,
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    "segs": [ {
      "utf8": "like combat or competitive sports."
    } ]
  }, {
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    "segs": [ {
      "utf8": "For example, about 50% of top hitters\nin baseball have been left-handed."
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  }, {
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    "segs": [ {
      "utf8": "Why?"
    } ]
  }, {
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    "segs": [ {
      "utf8": "Think of it as a surprise advantage."
    } ]
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      "utf8": "Because lefties are a minority\nto begin with,"
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  }, {
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    "segs": [ {
      "utf8": "both right-handed\nand left-handed competitors"
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  }, {
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    "segs": [ {
      "utf8": "will spend most of their time\nencountering"
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  }, {
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  }, {
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    "segs": [ {
      "utf8": "So when the two face each other,"
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      "utf8": "the left-hander will be better prepared\nagainst this right-handed opponent,"
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    "tStartMs": 165430,
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    "segs": [ {
      "utf8": "while the righty will be thrown off."
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  }, {
    "tStartMs": 168260,
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    "segs": [ {
      "utf8": "This fighting hypothesis,"
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  }, {
    "tStartMs": 169897,
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    "segs": [ {
      "utf8": "where an imbalance in the population"
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  }, {
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    "segs": [ {
      "utf8": "results in an advantage for left-handed\nfighters or athletes,"
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  }, {
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    "segs": [ {
      "utf8": "is an example of negative\nfrequency-dependent selection."
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    "segs": [ {
      "utf8": "But according to the principles\nof evolution,"
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    "tStartMs": 181599,
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    "segs": [ {
      "utf8": "groups that have a relative advantage"
    } ]
  }, {
    "tStartMs": 183385,
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    "segs": [ {
      "utf8": "tend to grow until\nthat advantage disappears."
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  }, {
    "tStartMs": 187219,
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    "segs": [ {
      "utf8": "If people were only fighting and competing\nthroughout human evolution,"
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      "utf8": "natural selection would lead to more\nlefties being the ones that made it"
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      "utf8": "until there were so many of them,"
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      "utf8": "that it was no longer a rare asset."
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      "utf8": "So in a purely competitive world,"
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      "utf8": "50% of the population\nwould be left-handed."
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    "segs": [ {
      "utf8": "But human evolution has been shaped\nby cooperation, as well as competition."
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      "utf8": "And cooperative pressure"
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  }, {
    "tStartMs": 210223,
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    "segs": [ {
      "utf8": "pushes handedness distribution\nin the opposite direction."
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  }, {
    "tStartMs": 214786,
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    "segs": [ {
      "utf8": "In golf, where performance\ndoesn't depend on the opponent,"
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  }, {
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      "utf8": "only 4% of top players are left-handed,"
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  }, {
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    "segs": [ {
      "utf8": "an example of the wider phenomenon\nof tool sharing."
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  }, {
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    "segs": [ {
      "utf8": "Just as young potential golfers"
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    "segs": [ {
      "utf8": "can more easily find\na set of right-handed clubs,"
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  }, {
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    "segs": [ {
      "utf8": "many of the important instruments\nthat have shaped society"
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  }, {
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    "segs": [ {
      "utf8": "were designed for\nthe right-handed majority."
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  }, {
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    "segs": [ {
      "utf8": "Because lefties are worse\nat using these tools,"
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  }, {
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    "segs": [ {
      "utf8": "and suffer from higher accident rates,"
    } ]
  }, {
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    "segs": [ {
      "utf8": "they would be less successful\nin a purely cooperative world,"
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  }, {
    "tStartMs": 244913,
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    "segs": [ {
      "utf8": "eventually disappearing\nfrom the population."
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  }, {
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    "segs": [ {
      "utf8": "So by correctly predicting\nthe distribution"
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  }, {
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    "segs": [ {
      "utf8": "of left-handed people\nin the general population,"
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  }, {
    "tStartMs": 252846,
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    "segs": [ {
      "utf8": "as well as matching data\nfrom various sports,"
    } ]
  }, {
    "tStartMs": 255653,
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    "segs": [ {
      "utf8": "the model indicates"
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  }, {
    "tStartMs": 256699,
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    "segs": [ {
      "utf8": "that the persistence of lefties\nas a small but stable minority"
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  }, {
    "tStartMs": 260499,
    "dDurationMs": 1959,
    "segs": [ {
      "utf8": "reflects an equilibrium"
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    "segs": [ {
      "utf8": "that comes from competitive\nand cooperative effects"
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  }, {
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    "segs": [ {
      "utf8": "playing out simultaneously over time."
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    "segs": [ {
      "utf8": "And the most intriguing thing"
    } ]
  }, {
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    "segs": [ {
      "utf8": "is what the numbers can tell us\nabout various populations."
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    "segs": [ {
      "utf8": "From the skewed distribution of pawedness\nin cooperative animals,"
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    "segs": [ {
      "utf8": "to the slightly larger\npercentage of lefties"
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    "segs": [ {
      "utf8": "in competitive hunter-gatherer societies,"
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  }, {
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    "segs": [ {
      "utf8": "we may even find that the answers\nto some puzzles of early human evolution"
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    "segs": [ {
      "utf8": "are already in our hands."
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