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    "segs": [ {
      "utf8": "This video is about natural selection."
    } ]
  }, {
    "tStartMs": 2530,
    "dDurationMs": 7370,
    "segs": [ {
      "utf8": "If you've watched the previous videos in this series, you've seen these blob creatures live, die, and replicate; but it's been a little bit artificial."
    } ]
  }, {
    "tStartMs": 10630,
    "dDurationMs": 4939,
    "segs": [ {
      "utf8": "We just gave each type of creature a replication chance and a death chance and we saw what happened."
    } ]
  }, {
    "tStartMs": 16150,
    "dDurationMs": 1879,
    "segs": [ {
      "utf8": "With natural selection though,"
    } ]
  }, {
    "tStartMs": 18029,
    "dDurationMs": 7950,
    "segs": [ {
      "utf8": "we usually can't know precise replication and death chances. Instead, selection comes from interactions between a creature's traits and its environment."
    } ]
  }, {
    "tStartMs": 26830,
    "dDurationMs": 6379,
    "segs": [ {
      "utf8": "So in this video we're going to make a real evolving system by putting our blob creatures into a simple environment and giving them traits."
    } ]
  }, {
    "tStartMs": 33640,
    "dDurationMs": 3590,
    "segs": [ {
      "utf8": "Let's see what we can learn by watching some actual natural selection happen."
    } ]
  }, {
    "tStartMs": 40570,
    "dDurationMs": 2029,
    "segs": [ {
      "utf8": "Alright so what does our environment look like?"
    } ]
  }, {
    "tStartMs": 43120,
    "dDurationMs": 6020,
    "segs": [ {
      "utf8": "Creatures will live on this plane, and each morning, food appears on the plane and the blobs emerge from their homes around the edge to"
    } ]
  }, {
    "tStartMs": 49140,
    "dDurationMs": 1960,
    "segs": [ {
      "utf8": "go out and eat the food."
    } ]
  }, {
    "tStartMs": 51100,
    "dDurationMs": 4459,
    "segs": [ {
      "utf8": "Here are the rules: if a blob fails to find any food before running out of energy,"
    } ]
  }, {
    "tStartMs": 55560,
    "dDurationMs": 740,
    "segs": [ {
      "utf8": "it will die."
    } ]
  }, {
    "tStartMs": 56920,
    "dDurationMs": 3520,
    "segs": [ {
      "utf8": "If a blob gets one piece of food and manages to get back home to the edge,"
    } ]
  }, {
    "tStartMs": 60440,
    "dDurationMs": 2040,
    "segs": [ {
      "utf8": "it will live on to the next day."
    } ]
  }, {
    "tStartMs": 62829,
    "dDurationMs": 2420,
    "segs": [ {
      "utf8": "And, if a blob gets two pieces and gets home,"
    } ]
  }, {
    "tStartMs": 65250,
    "dDurationMs": 4529,
    "segs": [ {
      "utf8": "it will survive to the next day and also replicate, adding another creature to the next day."
    } ]
  }, {
    "tStartMs": 70600,
    "dDurationMs": 4129,
    "segs": [ {
      "utf8": "So that's the environment. Before we talk about a creatures traits and how they might vary,"
    } ]
  }, {
    "tStartMs": 74729,
    "dDurationMs": 2819,
    "segs": [ {
      "utf8": "let's just watch these creatures live their lives for a few generations."
    } ]
  }, {
    "tStartMs": 89680,
    "dDurationMs": 4939,
    "segs": [ {
      "utf8": "So we see that these creatures can manage to live over several generations in this environment and"
    } ]
  }, {
    "tStartMs": 94810,
    "dDurationMs": 6529,
    "segs": [ {
      "utf8": "The number of creatures actually expanded over the first few days and then leveled off. So the population started out below the carrying capacity"
    } ]
  }, {
    "tStartMs": 101710,
    "dDurationMs": 5809,
    "segs": [ {
      "utf8": "but once the population expanded to around 95, the creatures really had to compete with each other for food."
    } ]
  }, {
    "tStartMs": 108549,
    "dDurationMs": 6230,
    "segs": [ {
      "utf8": "Once we allow mutations, the variation will give some creatures an advantage and we'll start seeing some natural selection of traits."
    } ]
  }, {
    "tStartMs": 114819,
    "dDurationMs": 2480,
    "segs": [ {
      "utf8": "So let's turn on mutations and see what happens."
    } ]
  }, {
    "tStartMs": 117789,
    "dDurationMs": 4669,
    "segs": [ {
      "utf8": "Let's start out with one trade varying: speed. Each time a creature replicates,"
    } ]
  }, {
    "tStartMs": 122459,
    "dDurationMs": 5250,
    "segs": [ {
      "utf8": "there's a chance that a mutation will give the new creature a slightly lower or slightly higher speed."
    } ]
  }, {
    "tStartMs": 128470,
    "dDurationMs": 5599,
    "segs": [ {
      "utf8": "Speed is great because it allows you to beat other creatures to the food; but speed will also have a cost:"
    } ]
  }, {
    "tStartMs": 134440,
    "dDurationMs": 1730,
    "segs": [ {
      "utf8": "moving quickly is less efficient."
    } ]
  }, {
    "tStartMs": 136170,
    "dDurationMs": 6419,
    "segs": [ {
      "utf8": "If a creature speed is doubled, it will cover a distance in half the time but use twice as much energy to go that distance."
    } ]
  }, {
    "tStartMs": 143230,
    "dDurationMs": 5599,
    "segs": [ {
      "utf8": "Faster creatures can't forage over as much ground as slower creatures, so they might not find food before running out of energy."
    } ]
  }, {
    "tStartMs": 149709,
    "dDurationMs": 5869,
    "segs": [ {
      "utf8": "If we unpause this world with speed mutations turned on, what would you predict? When the faster creatures start appearing,"
    } ]
  }, {
    "tStartMs": 155579,
    "dDurationMs": 4440,
    "segs": [ {
      "utf8": "will they sprint to victory? Or will the slower creatures prove the virtue of patience?"
    } ]
  }, {
    "tStartMs": 160480,
    "dDurationMs": 6319,
    "segs": [ {
      "utf8": "It could also turn out that the current creatures have struck a good balance, or it could be that being fast and being slow are"
    } ]
  }, {
    "tStartMs": 166799,
    "dDurationMs": 6570,
    "segs": [ {
      "utf8": "both good strategies; it's hard to say at this point. We'll just have to unpause and see what the nature of the situation is."
    } ]
  }, {
    "tStartMs": 174720,
    "dDurationMs": 2480,
    "segs": [ {
      "utf8": "Let's speed it up a bit so we can see more generations."
    } ]
  }, {
    "tStartMs": 187840,
    "dDurationMs": 2960,
    "segs": [ {
      "utf8": "All right, so it turns out to be worth sacrificing"
    } ]
  }, {
    "tStartMs": 191320,
    "dDurationMs": 5660,
    "segs": [ {
      "utf8": "efficiency for speed in this environment. Or, at least the initial speed value I picked was slower than optimal."
    } ]
  }, {
    "tStartMs": 197410,
    "dDurationMs": 2179,
    "segs": [ {
      "utf8": "This is our first example of natural selection."
    } ]
  }, {
    "tStartMs": 200290,
    "dDurationMs": 6949,
    "segs": [ {
      "utf8": "We didn't know the best speed value going in, but the creatures mutated and somewhat randomly tried out different speed values, and then through"
    } ]
  }, {
    "tStartMs": 207239,
    "dDurationMs": 6750,
    "segs": [ {
      "utf8": "natural selection the population evolved to have a higher average speed over time. I want to double down on that last point: the"
    } ]
  }, {
    "tStartMs": 214599,
    "dDurationMs": 3050,
    "segs": [ {
      "utf8": "*population* evolved. As much as we all love Pokemon,"
    } ]
  }, {
    "tStartMs": 218200,
    "dDurationMs": 2419,
    "segs": [ {
      "utf8": "individuals don't evolve in the biological sense of the word."
    } ]
  }, {
    "tStartMs": 221670,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "Populations evolve over generations."
    } ]
  }, {
    "tStartMs": 224730,
    "dDurationMs": 3199,
    "segs": [ {
      "utf8": "One interesting thing to notice is that as the average speed of the"
    } ]
  }, {
    "tStartMs": 228030,
    "dDurationMs": 3649,
    "segs": [ {
      "utf8": "population went up, the number of creatures in any given day tended to go down."
    } ]
  }, {
    "tStartMs": 231930,
    "dDurationMs": 3559,
    "segs": [ {
      "utf8": "The creatures now compete more fiercely and are less efficient overall."
    } ]
  }, {
    "tStartMs": 236069,
    "dDurationMs": 2930,
    "segs": [ {
      "utf8": "This is part of the meaning of the term \"Selfish Gene\"."
    } ]
  }, {
    "tStartMs": 239639,
    "dDurationMs": 3350,
    "segs": [ {
      "utf8": "We'll talk more about genes and the term \"Selfish Gene\" in future videos,"
    } ]
  }, {
    "tStartMs": 242989,
    "dDurationMs": 7050,
    "segs": [ {
      "utf8": "but for now just notice that even though we might call these creatures better because they did better in the competition for survival, the total"
    } ]
  }, {
    "tStartMs": 250040,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "population size actually went down."
    } ]
  }, {
    "tStartMs": 252329,
    "dDurationMs": 4880,
    "segs": [ {
      "utf8": "Selection didn't happen for the good of the species as a whole, but again, more on that in future videos."
    } ]
  }, {
    "tStartMs": 258239,
    "dDurationMs": 6679,
    "segs": [ {
      "utf8": "Alright, now that we've gotten our feet wet with one varying trait, let's add two more: size and sense. First, size."
    } ]
  }, {
    "tStartMs": 265860,
    "dDurationMs": 2210,
    "segs": [ {
      "utf8": "Size scales the creature in all three dimensions."
    } ]
  }, {
    "tStartMs": 268650,
    "dDurationMs": 5209,
    "segs": [ {
      "utf8": "The benefit of size is that it lets you eat other creatures if you're at least 20% larger than them."
    } ]
  }, {
    "tStartMs": 274410,
    "dDurationMs": 1610,
    "segs": [ {
      "utf8": "Getting an extra food source is great"
    } ]
  }, {
    "tStartMs": 276020,
    "dDurationMs": 810,
    "segs": [ {
      "utf8": "if you can pull it off,"
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  }, {
    "tStartMs": 276830,
    "dDurationMs": 5690,
    "segs": [ {
      "utf8": "but being big costs a lot of energy. The energy cost depends on the cube of a creature size value"
    } ]
  }, {
    "tStartMs": 283080,
    "dDurationMs": 2580,
    "segs": [ {
      "utf8": "I could have picked any function for the energy cost I suppose,"
    } ]
  }, {
    "tStartMs": 285720,
    "dDurationMs": 3700,
    "segs": [ {
      "utf8": "but I made it a cube because volume scales as the cube of length, and"
    } ]
  }, {
    "tStartMs": 289710,
    "dDurationMs": 2720,
    "segs": [ {
      "utf8": "volume is closely linked to the mass a creature has to carry around."
    } ]
  }, {
    "tStartMs": 293190,
    "dDurationMs": 5869,
    "segs": [ {
      "utf8": "The total energy cost of a creature's movement each time step is equal to the cube of the creature's size"
    } ]
  }, {
    "tStartMs": 299370,
    "dDurationMs": 6950,
    "segs": [ {
      "utf8": "times the square of the creatures speed from before, which you might notice is reminiscent of the formula for kinetic energy."
    } ]
  }, {
    "tStartMs": 306330,
    "dDurationMs": 829,
    "segs": [ {
      "utf8": "But anyway,"
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  }, {
    "tStartMs": 307159,
    "dDurationMs": 3240,
    "segs": [ {
      "utf8": "it's especially costly to be both big and fast."
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  }, {
    "tStartMs": 310650,
    "dDurationMs": 4639,
    "segs": [ {
      "utf8": "And, on top of this cost, smaller creatures will actually run from creatures big enough to eat them."
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  }, {
    "tStartMs": 315530,
    "dDurationMs": 2970,
    "segs": [ {
      "utf8": "So, to benefit from being big, you need at least some speed."
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  }, {
    "tStartMs": 319020,
    "dDurationMs": 2809,
    "segs": [ {
      "utf8": "Long story short, being big is high-risk and high-reward."
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  }, {
    "tStartMs": 323219,
    "dDurationMs": 1711,
    "segs": [ {
      "utf8": "The third trait is sense."
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  }, {
    "tStartMs": 324930,
    "dDurationMs": 4549,
    "segs": [ {
      "utf8": "Each creature has a certain sensing distance at which it can sense food or other creatures."
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  }, {
    "tStartMs": 329880,
    "dDurationMs": 5899,
    "segs": [ {
      "utf8": "Once a creature sees food or a smaller creature, it can move straight toward it. Or, if it sees a bigger creature it can run away."
    } ]
  }, {
    "tStartMs": 336780,
    "dDurationMs": 7100,
    "segs": [ {
      "utf8": "This sensing distance gets larger as a creature's sense rate goes up, allowing it to avoid danger and be more efficient with its movements."
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  }, {
    "tStartMs": 344130,
    "dDurationMs": 5119,
    "segs": [ {
      "utf8": "Each time step, a creature pays a movement energy cost which depends on its size and speed, and"
    } ]
  }, {
    "tStartMs": 349380,
    "dDurationMs": 3229,
    "segs": [ {
      "utf8": "a sensing energy cost which is just equal to its sense rate."
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  }, {
    "tStartMs": 353730,
    "dDurationMs": 1640,
    "segs": [ {
      "utf8": "All right, so now that we have three traits,"
    } ]
  }, {
    "tStartMs": 355370,
    "dDurationMs": 5550,
    "segs": [ {
      "utf8": "let's rewind to before we turned on speed mutations, and instead, turn on mutations for all three traits."
    } ]
  }, {
    "tStartMs": 361290,
    "dDurationMs": 2630,
    "segs": [ {
      "utf8": "To keep track of what's happening to all three traits at once,"
    } ]
  }, {
    "tStartMs": 363920,
    "dDurationMs": 2069,
    "segs": [ {
      "utf8": "we're going to use this three dimensional graph."
    } ]
  }, {
    "tStartMs": 366480,
    "dDurationMs": 7279,
    "segs": [ {
      "utf8": "Each dot in the graph represents one creature, and the position of the dot depends on the speed, size, and sense values for that creature."
    } ]
  }, {
    "tStartMs": 374970,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "All right, let's see how it goes."
    } ]
  }, {
    "tStartMs": 391680,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "So what can we say about the results?"
    } ]
  }, {
    "tStartMs": 394350,
    "dDurationMs": 2660,
    "segs": [ {
      "utf8": "The first thing I notice is that the average speed is"
    } ]
  }, {
    "tStartMs": 397110,
    "dDurationMs": 6230,
    "segs": [ {
      "utf8": "significantly different from what it was when only speed was allowed to vary, which is a little bit surprising because we didn't explicitly change"
    } ]
  }, {
    "tStartMs": 403340,
    "dDurationMs": 6209,
    "segs": [ {
      "utf8": "anything about how speed works. But with sense and size able to vary, different creatures were able to appear."
    } ]
  }, {
    "tStartMs": 409919,
    "dDurationMs": 6920,
    "segs": [ {
      "utf8": "A creature's environment includes all the creatures around it, and for whatever reason, speed just wasn't as valuable this time around."
    } ]
  }, {
    "tStartMs": 417390,
    "dDurationMs": 3139,
    "segs": [ {
      "utf8": "And there's one other thing I noticed: when I first ran the simulation,"
    } ]
  }, {
    "tStartMs": 420600,
    "dDurationMs": 3679,
    "segs": [ {
      "utf8": "I thought there would be a pretty intense selection toward creatures with higher sense,"
    } ]
  }, {
    "tStartMs": 424350,
    "dDurationMs": 3679,
    "segs": [ {
      "utf8": "because sense informs everything else that creature does and it doesn't cost very much."
    } ]
  }, {
    "tStartMs": 428310,
    "dDurationMs": 4520,
    "segs": [ {
      "utf8": "But instead, sense is fairly spread out and centered roughly around the starting value."
    } ]
  }, {
    "tStartMs": 433350,
    "dDurationMs": 5959,
    "segs": [ {
      "utf8": "That's the thing about natural selection. It doesn't care what I or anyone else thinks is best. It. Just does what it does."
    } ]
  }, {
    "tStartMs": 439919,
    "dDurationMs": 1291,
    "segs": [ {
      "utf8": "All right,"
    } ]
  }, {
    "tStartMs": 441210,
    "dDurationMs": 7010,
    "segs": [ {
      "utf8": "one last simulation. Let's see what happens if we change the environment more explicitly. Let's go to ten food each day."
    } ]
  }, {
    "tStartMs": 448890,
    "dDurationMs": 4129,
    "segs": [ {
      "utf8": "It's pretty clear that this won't be able to support the population of about 50 creatures"
    } ]
  }, {
    "tStartMs": 453020,
    "dDurationMs": 6240,
    "segs": [ {
      "utf8": "we currently have, so the number of creatures will go down. But what else will happen? I don't know. We'll just have to see."
    } ]
  }, {
    "tStartMs": 461880,
    "dDurationMs": 1530,
    "segs": [ {
      "utf8": "Hm."
    } ]
  }, {
    "tStartMs": 463410,
    "dDurationMs": 770,
    "segs": [ {
      "utf8": "Okay, well,"
    } ]
  }, {
    "tStartMs": 464180,
    "dDurationMs": 580,
    "segs": [ {
      "utf8": "apparently,"
    } ]
  }, {
    "tStartMs": 464760,
    "dDurationMs": 4190,
    "segs": [ {
      "utf8": "the creatures that thrived with 100 food just aren't able to cut it with only ten,"
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  }, {
    "tStartMs": 469080,
    "dDurationMs": 2689,
    "segs": [ {
      "utf8": "even though there should be enough for, say, five to ten creatures."
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  }, {
    "tStartMs": 472020,
    "dDurationMs": 4010,
    "segs": [ {
      "utf8": "So it looks like if it's going to be possible to survive with only ten food,"
    } ]
  }, {
    "tStartMs": 476160,
    "dDurationMs": 3109,
    "segs": [ {
      "utf8": "there's gonna have to be some time for the population to adjust."
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  }, {
    "tStartMs": 480000,
    "dDurationMs": 770,
    "segs": [ {
      "utf8": "So instead,"
    } ]
  }, {
    "tStartMs": 480770,
    "dDurationMs": 570,
    "segs": [ {
      "utf8": "let's do this:"
    } ]
  }, {
    "tStartMs": 481340,
    "dDurationMs": 6209,
    "segs": [ {
      "utf8": "we'll rewind to before we reduce the food and then every two days we'll put out one less piece of food until eventually we're"
    } ]
  }, {
    "tStartMs": 487630,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "only putting out 10 pieces of food each day."
    } ]
  }, {
    "tStartMs": 499010,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "All right..."
    } ]
  }, {
    "tStartMs": 504200,
    "dDurationMs": 6169,
    "segs": [ {
      "utf8": "So it's not too surprising that in a lower food environment, things aren't just crowded and being big just isn't worth it anymore."
    } ]
  }, {
    "tStartMs": 510710,
    "dDurationMs": 6740,
    "segs": [ {
      "utf8": "Sense, on the other hand, became super valuable now that a low sense creature can easily go a whole day without seeing anything, and die."
    } ]
  }, {
    "tStartMs": 518300,
    "dDurationMs": 3440,
    "segs": [ {
      "utf8": "And now speed is actually really valuable again. This surprised me actually;"
    } ]
  }, {
    "tStartMs": 522010,
    "dDurationMs": 3059,
    "segs": [ {
      "utf8": "I thought in a sparse environment that efficiency would be king,"
    } ]
  }, {
    "tStartMs": 525170,
    "dDurationMs": 6290,
    "segs": [ {
      "utf8": "making both size and speed go down, but apparently speed is actually more valuable now. So again, I can't predict it."
    } ]
  }, {
    "tStartMs": 531740,
    "dDurationMs": 4580,
    "segs": [ {
      "utf8": "So other than reiterating the fact that I don't know what's going to happen, what can this teach us?"
    } ]
  }, {
    "tStartMs": 536990,
    "dDurationMs": 3619,
    "segs": [ {
      "utf8": "Well, to put it plainly: the environment matters. A lot."
    } ]
  }, {
    "tStartMs": 541310,
    "dDurationMs": 5570,
    "segs": [ {
      "utf8": "Reducing the amount of food didn't just reduce the number of creatures; it totally changed which creatures exist."
    } ]
  }, {
    "tStartMs": 549140,
    "dDurationMs": 6079,
    "segs": [ {
      "utf8": "You'll often see evolution depicted as this march toward more and more advanced or complex or higher creatures,"
    } ]
  }, {
    "tStartMs": 555290,
    "dDurationMs": 4880,
    "segs": [ {
      "utf8": "but that's not how it is at all. The only thing that matters is how well the creature is adapted to its environment."
    } ]
  }, {
    "tStartMs": 562460,
    "dDurationMs": 2719,
    "segs": [ {
      "utf8": "Okay, so, before we go, let's do a quick recap:"
    } ]
  }, {
    "tStartMs": 566000,
    "dDurationMs": 5150,
    "segs": [ {
      "utf8": "Even with this relatively simple environment we created, we were able to see some important principles in action."
    } ]
  }, {
    "tStartMs": 572060,
    "dDurationMs": 2359,
    "segs": [ {
      "utf8": "But we're not done yet. In the next few videos,"
    } ]
  }, {
    "tStartMs": 574420,
    "dDurationMs": 6360,
    "segs": [ {
      "utf8": "we'll keep exploring natural selection by trying to see how some more complicated and even counterintuitive traits can be favored."
    } ]
  }, {
    "tStartMs": 581540,
    "dDurationMs": 2000,
    "segs": [ {
      "utf8": "See you then!"
    } ]
  } ]
}