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Misunderstanding evolution: a biologist's perspective on Social Darwinism

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Video transcript

hey this is Kim from Khan Academy I am the history fellow here and I am here with Emily hi I'm the biology fellow so Emily and I are here talking about Darwinism and I'm interested in Darwinism because in the late 19th century I usually call the Gilded Age there is a very prominent interpretation of Darwinism that is called social Darwinism and social Darwinism wasn't so much an actual form of biology as it was kind of a misinterpretation of how natural selection and the theory of evolution worked that was used to justify or explain a lot of the social inequalities of this time period and the way people often thought about it was that white anglo-saxon people so Europeans Northern Europeans were kind of the most evolved and this is our timeline of evolution from least evolved to most evolved and people like african-americans or Asians or Native Americans or even Eastern Europeans were less evolved that they were on a scale of evolution where they hadn't come as far as anglo-saxons so Emily you're a biologist and I would love to get your take on how it is that natural selection actually works and how this doesn't quite describe what was really going on yeah definitely on so maybe I can speak first to that specific graph that you've drawn on and I think that this is actually a common point of confusion when it comes to evolution that there's not really such a thing as more or less evolved in evolution okay so this is this gradient really doesn't exist no I mean there's on there's sort of the I think that people sometimes see the pictures of like the eep standing up and turning into a person and they think oh this is sort of a linear path from one thing to another but what you really get is different types of organisms evolving from a shared ancestor and branching off so alright so nobody who's alive on earth today has been evolving for more or less time since their last common ancestor than anybody else so would you I'm gonna draw what I think is how you're explaining this and please correct me as I go along but say this is my common ancestor and then would there possibly be branches like this yeah that's a great way to draw it and I mean you know certainly humans are all extremely closely related to each other but like we could even say this for us versus a dog a bacteria like pretty much anything all life on Earth shares a common ancestor and so that bacteria is just as well as evolved as you are actually in the sense of absolute time since since those two split apart right so like from the moment that life first appeared on earth there has been so much time and all of us have been evolving from that point so even whether you're a piece of bacterial piece a good word of a bacterium there you go Nestle bacterium I I took biology once um or you are Albert Einstein you have been evolving for precisely the same amount of time yep awesome okay wow I'm really relieved to find that I could deserve it as well good you did a great job beautiful um so okay so you've done this this distinction between evolving from a common ancestor so how is it that the actual theory of natural selection works yeah that's a great question so natural selection often people talk about it as sort of having three key ingredients and to see how it works on let's imagine that we're just looking at a population of beetles so picture picture your beetles to start with on and what what would we need to have in order for these beetles as a group to evolve by natural selection so one thing that we would need is we would need some variation among the beetles so if you have identical beetles you're not going to have any that are better at surviving or reproducing than any others which is kind of a key ingredient for what we're going to talk about okay so I've got two different beetles here they're slightly different from each other awesome and you've made them different colors which is perfect so we have variation and in the next ingredient that we're going to need so we're going to need that variation to be heritable so we're going to say that those beetles one of them is green and one of them is blue and that's because of something in their DNA so they have differences in their DNA that create the variation in colors okay so all right so when you say heritable you mean that this is something that their descendants could inherit exactly that is that is exactly it so the final ingredient is that the difference is these heritable differences need to affect how good the beetles are at leaving offspring in the next generation okay so for example let's let's say we would probably have more than two beetles in our actual population but let's say this population has just moved into a new area that is very blue colored okay so blue rocks blue flowers whatever and there's also a bunch of birds in that environment that really like to eat beetles and I'm guessing that if they have blue beetles and green beetles that one of those is going to show up a lot better against the blue environment than the other so probably a lot of our green beetles are going to get picked off by birds and they're not going to be able to leave offspring because gosh they kind of got at so when you look at the next generation of beetles if we know that the colors get passed on we're going to probably see a bigger group of that a bigger proportion of that group being made up of Blue Beetle and less being made up of green and that is an example of natural selection and action where you can see that that organisms that survive and specifically reproduce better in a certain environment are going to increase in frequency in a population so you're going to get more and more of these blue guys less and less of the green guys is there a word you would use to describe this sort of this adaptation is that the natural selection part as from variation and heritable like the natural selection is just like a good situation yeah I mean natural natural selection is really the just the the differential survival and reproduction and as you you mentioned a great word there which is adaptation on so adaptation is is the word that biologists often give to the the process of a population getting better and better suited to its environment so you would say that the population was adapting to being in a blue space as it gradually started to have more and more blue beetles across generations so what I find really interesting about this is that it's entirely by chance right more or less you've got a genetic mutation and then that mutation happens to suit the environment that you're in which allows you to thrive and your jeans and your adaptations to be passed on over time yes and I mean the the variation would have occurred randomly to start with like you say it would have been a mutation it didn't happen because the Beatles went to a blue place and said gosh I should be blue that'd be awesome that was not what happened that it was already there and it just happened to be successful in that environment if they'd gone to a green place well guess what you would have gotten exactly the opposite effect suddenly the green guys would have been more successful more able to leave offspring and you would have seen green be increasing or quote-unquote favored by natural selection