Let’s Talk About Sex: Crash Course Psychology #27


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People have been having sex and writing songs about it and carving statues of it and changing
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fashion for it since the dawn of humanity, but it wasn’t until fairly recently in the
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1940s that serious Western scientific study of sex began. And by most accounts you can
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thank one guy for that: Alfred Kinsey.
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Kinsey was born in 1894 in New Jersey, to poor strict Methodist parents. He studied
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etymology in college, graduated with degrees in biology and psychology before heading to
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Harvard. His doctoral thesis was on the genealogy of Gall wasps, a subject he tackled with intensity;
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meticulously collecting over five million samples, measuring hundreds of thousands of
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specimens.
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And wasps are interesting and everything, but Kinsey’s interests drifted toward human
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sexuality and his research in Indiana University paved the way for decades of study into sex.
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He surveyed thousands of men and women about their sexual habits and histories, and found
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all sorts of interesting things related to sexual preferences, masturbation, orgasms,
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and pre-marital sex. He established the “Kinsey scale” indicating degrees of sexual orientation)
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and went on to write the seminal texts on sexual behavior in the human male and female
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respectively.
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Like many researchers of human behavior, Kinsey and his colleagues were – and in some ways
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still are – pretty controversial. But he definitely succeeded in two very important tasks. One:
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he was an early adopter of a scientific approach to studying sex, and two: he showed that the
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popular perception of what people do and don’t do sexually, versus what people actually do
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and feel, was often very different.
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Since then we’ve seen innumerable sex-related studies examining the physiological and psychological
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and social elements of sex.
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And, there’s a whole lot of lingering misinformation and judging morality swirling around the subject
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of sex. It can be a tricky topic for sure but we are here to clear some things up. It’s
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the entire purpose of life so there’s no reason to blush.
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So. Sex.
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That one little word has complicated so many lives. The desire for or lack of sex has spawned
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poetry and made babies and transmitted diseases and cost money and driven people batty and
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kept late-night cable in business.
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Even the word itself can mean many different things.
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First we’ve got the verb kind of sex, the physical process of engaging in sexual acts
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and intercourse, which, probably I don’t need to describe to you.
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Then we’ve got the biological definition, having to do with the anatomical parts that
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go with the designations of male or female or intersex – those who were born with the
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reproductive parts that don’t fall into the predominant definitions of male or female.
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And these are quite separate from gender, or an individual’s sense of identifying as
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male or female or another gender identity regardless of how that corresponds with their
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actual reproductive plumbing. For transgender people, for instance, gender identity typically
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doesn’t match biological sex.
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And remember that gender identity is completely different from sexual orientation, which we’ll
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talk about in a minute.
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So beyond definitions, we have the physiological and psychological aspects of sex.
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Let’s start with the physiological, and with that, Masters and Johnson.
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In the late 1950’s and 60’s, American gynecologists Williams Masters, and his collaborator and
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future wife, sexologist Virginia Johnson, did something no researchers had ever done
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before. They invited nearly 700 male and female volunteers, many of them sex workers, to come
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into their lab and get it on, either alone or with their partners.
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Their aim? To record the body’s physiological response to sex. This involved wearing a whole
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lot of wires and heart monitors and such, and is probably about as sexy as it sounds.
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All the volunteers had to be willing and able to show arousal and be capable of orgasm.
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And over the years, Masters and Johnson recorded more than ten thousand “sexual cycles”. The
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main thing they documented was that a complete sexual response cycle involved four distinct
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stages – excitement, plateau, orgasm, and resolution – which Masters and Johnson maintained
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happened in a linear way, one after the other.
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In the excitement phase, things are gettin’ goin’, blood is rushing to all the necessary
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places, genital areas are becoming engorged and secreting lubricant. Next comes the plateau
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phase. Pulse, blood pressure, and breathing rates keep increasing and genitals are becoming
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fully engorged. The penis is often secreting pre-ejaculate as vaginal secretions increase
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until the big event orgasm during which muscles all over the body contract and breathing and
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pulse rates hit their peak.
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Of course, a biological male orgasm typically releases sperm that may lead to fertilization,
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depending on the situation, but female arousal and orgasm also help facilitate conception,
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again depending on the situation as those muscle contractions and lubrication help draw
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up and retain sperm in the uterus.
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Finally, the body comes back down to its normal state of affairs during the resolution phase.
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It’s during this phase that biosex males enter a refractory period during which they’re unable
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to orgasm again for a few minutes to a day or more whereas biological females refractory
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period is very short in comparison.
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While the four stage model of sexual response is still taught today, some have criticized
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both its rigid linear setup, arguing that things don’t always work so tidily in the
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bedroom, and it’s insistence in including orgasm which doesn’t happen for everyone all
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the time. Others also question the model’s clinical focus on only physiological factors
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arguing the cultural attitudes, psychological and relationship factors, and other external
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details should also be considered when looking at sexual response.
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I’ll get back to that in a minute, but before we move on to the psychology of sex, we got
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to talk about hormones.
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You remember hormones, those chemical messengers brewed up by the endocrine system that travel
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through the bloodstream and regulate all sorts of physiological and behavioral activities
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from growth to digestion to sleep to sex.
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Our sex hormones serve two major purposes. One, they direct the physical development
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of biological sex characteristics, and two, they help activate sexual behavior.
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Estrogens like estradiol contribute to female sex characteristics and are secreted in greater
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amounts by females than males and while all humans make testosterone, it’s the predominate
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sex hormone for males, stimulating the growth and development of male sex characteristics.
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Now most female mammals become sexually receptive when their estrogens peak during ovulation,
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but it doesn’t really work that way for humans. Our hormones are more loosely related to sexual
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behavior, although studies have found that in general female’s sexual desire spikes slightly
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around ovulation, when woman are most fertile and males can also be affected by this spike,
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responding with higher levels of testosterone when ovulating women are around.
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But these short term changes hardly compare to the larger more major hormonal shifts that
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occur throughout a life time.
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Puberty, for one, tends to get everyone a lot more hot and bothered and interested in
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dating and gazing at posters of their favorite celebrity crushes and later in life, as sex
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hormone production normally decreases, our amorous urges and endeavors tend to decrease
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as well.
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Age affects our libido. But in the end you might think of sex hormones as fuel for your
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sexual engine, and while an engine can’t run on a totally empty tank, it also won’t run
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any better or worse on a full tank versus a half tank. We need our sex hormones, but
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we also need the right psychological stimuli to turn us on and keep us going sexually.
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So, finally, let’s look at some of these psychological aspects of sex. First, there are the very
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important social and cultural influences. Things like your families, your societies,
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your religions, and your personal values. Does your community view sex merely as the
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means for reproduction or can it be fun too? What are the views on premarital sex, and
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homosexuality, showing some skin or kissing in public?
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Then there are the influences of external stimuli. In western society, we’re constantly
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bombarded with sexually charged content from movies and TV to advertisements, R&B; slow
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jams, and Victoria Secret catalogs. And constantly looking at images of things that you find
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extremely attractive can lead to folks viewing more average people, even their own partners,
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as being less attractive.
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But our sexual desire is also fueled by internal stimuli. Our imagination and memories and
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fantasies. According to plenty of studies, at least 95% of people fantasize about sex
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at some point. The thing you need to keep in mind is that none of these factors work
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independently of each other. How we respond to both external and internal stimuli can
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be really heavily influenced by social and cultural factors, and that is where a lot
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of the thinking and studying of sex has gotten really complicated.
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Human judgment and morality is often entangled with sex and desire and sadly, a lot of people
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have been made to feel miserable for liking certain things or being attracted to certain
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people. There’s also just been a lot of misinformation out there. For ages, a lot of folks believed
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that masturbation could make you go blind, become mentally ill, or kill the neighborhood
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kittens. It doesn’t do that.
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And as I know, you’re thinking right now one area of sexuality has been needlessly associated
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with conflict, fear, and shame in many cultures is sexual orientation.
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For our purposes, sexual orientation can be defined as a relatively enduring physical
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or romantic attraction to another person. Heterosexual, homosexual, and bisexual are
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all types of sexual orientation. And although the field once stigmatized non-heterosexual
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orientations, we now know that homosexuality and bisexuality are in no way related to mental
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health.
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Psychologists are also beginning to look more in depth at other sexual orientations. For
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instance, Asexuality or nonsexuality, where no sexual attraction of any kind is experienced.
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In any case, whether a culture itself is friendly to or tyrannical against any of these orientations,
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all types prevail. Sexual orientation is neither chosen nor changed.
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So, what might cause these differences? Hopefully you already know this but it’s worth repeating.
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There’s no evidence that sexual orientation is determined by things like dominating mother
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or passive father or sex hormone levels in your adult body or your history of childhood
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abuse or whether your parents were gay or straight. In other words, decades of research
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have led most researchers to believed that once you’re born, there are no clear environmental
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factors that influence your sexual orientation.
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And there’s been a lot of research into possible biological components of sexual orientation,
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like genetics, brain anatomy, prenatal conditions, or other things. It’s also important to know
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that we’re far from understanding sexual orientation on a purely biological level. If anything,
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the evidence we’ve got simply strengthens the idea that sexual orientation isn’t choice,
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but rather a naturally varying occurrence among human beings, like height.
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So.
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After all this talk about sex, perhaps you’re wondering why we do it at all. I mean, it
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feels good obviously. But the biggest function of sex goes beyond pure pleasure. In fact,
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sexual intimacy serves many of life’s most basic purposes: some times procreation, but
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also stress reduction, maintaining healthy relationships, social bonding, and the expression
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of love, and overall fulfillment.
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People say he brain is the most significant sex organ for a reason. And intimacy is often
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its own reward.
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Today, you learned about Alfred Kinsey’s ground breaking sex surveys, the differences between
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how we define biological sex and gender identity, and about Masters and Johnson’s four-part
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sexual response cycle.
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We also looked at the role of sex hormones, in our development and drive, how psychological
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and social factors play into sex, how we think about sexual orientation and why we have sex
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in the first place.
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Thanks for watching, especially to our Subbable subscribers who make crash course possible.
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To find out how you can become a supporter, just go to subbable.com/crashcourse.
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This episode was written by Kathleen Yale, edited by Blake de Pastino, and our consultant
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is Dr. Ranjit Bhagwat. Our director and editor is Nicholas Jenkins, our sound designer is
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Michael Aranda, and the graphics team is Thought Cafe.


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Photo credit: Screenshot from video.