Hi. In this video, we're going to be talking about the history of genetics. Okay. So I know if you're anything like me, history is probably not your favorite subject. That's okay though, but history in genetics for some reason is really important. The professors of genetics really like hitting you with history questions. So throughout the whole semester, if I'm giving you, you know, dates and names and people, I'm going to tell you, you know, these names are important, these dates are important, these concepts are important because for some reason, geneticists love to test and quiz you on history. But for this, we're going to start way back. I mean, like, the very earliest time that I think you'll probably ever even talk about in a science class, and that is, you know, 8,000 to 1,000 BC. And this is when genetics really first came about. Not the genetics we have today, but really the genetics that they had then was things like domestication. And that's domestication of animals. Things like, you know, the wolves, the dogs, domestication. That's cultivation of plants, that they could eat and harvest and raise as people started, you know, grouping together, living together. They needed food sources. They needed animals, and so they domesticated things. And so this type of genetics is actually called selective breeding or artificial selection, and, essentially this is the process of taking organisms with certain traits and mating them together to propagate that trait. So, although carrots didn't really exist in the same way back then, but if you had an orange carrot and you wanted more orange carrots, what you would do is you would mate orange carrots together and you keep getting orange carrots. For dogs, you take, you know, these gentle wolves, and you mate them together, and eventually over time they turn into these gentle dogs, which are completely different species, but, this is this type of breeding. You're selecting for certain traits. At the time, though, I mean, obviously, no one knew at all what controlled this. They had no idea. They were hoping that, you know, you mate 2 orange carrots together, you get another orange carrot, but they didn't know. Right? And sometimes you don't, and sometimes there are these unique genetic traits that we'll talk about where you mate 2 orange carrots together, sometimes you get a purple carrot. And these types of genetics, they had no idea how to control, but they did their best, and so they were like, you know, most likely this will work, so that's what we're going to keep doing. And so they use the principle like begets like. So things that are like will keep producing those things. So orange carrots will likely keep producing orange carrots. And so here are some carrots, for instance, that have undergone artificial selection so that you can get all these different colors. They're pretty much all the same size, but, all these different colors, you know, were bred for that trait or some trait that gave them these colors, an example of artificial selection.
Now we're going to jump forward a lot further, so now we're in 300 BC. And this is when Aristotle and the Hippocratic School of Medicine started coming about and proposing some theories about, how, you know, inheritance worked. They could see that, you know, children often look like their parents, but they really had no idea how that happened. And up until then, all they had was life begets life. So what they did is they proposed this idea, this pangenesis. And this uses these particles called gemmules. And gemmules, they believed, were these particles that existed in every part of the body. So there were brain ones, there were eye gemmules, there were hand gemmules, leg gemmules, kidney gemmules, all these gemmules that existed in every part of the body, and they traveled to the reproductive organs. And so when they made it to the reproductive organs, these gemmules were then able to be passed on to the offspring, and that is what allowed children to look like their parents. But this allows for something interesting, including the inheritance of acquired characteristics. So, for instance, if a man is a really great musician, and so he spent his whole life acquiring this musical talent, then he'll have these special musical gemmules in his body, and those would travel to the reproductive organs and be transferred to the offspring, giving that offspring a much higher chance of being, you know, really great at music. And so that's what they believed here.
So here's an example of what this looks like, all these little circles that are the gemmules, and you can see there's some here, some in the brain. Let me choose a different color. Oh, I chose black. Let me choose red. There we go. There's some in the leg, all over, and they all travel to the reproductive organ. They get into the eggs of the sperm, and then that is going to be passed on to the offspring. So that was kind of the theory at the time, and that actually remained for a very long period of time.
Because now we're going to jump ahead to 1650-1850 AD. And this is when two more theories of inheritance came about. The first is epigenesis. And this says that organisms or offspring are derived from substances found in the sex cells, so found in the sperm or egg. Now this is actually almost right. I mean, it is right. Right? They didn't know what these substances were, but they said, you know, the sex cells contain the information to make the offspring. So this was actually very intuitive. But the conflicting theory at the time was this theory of preformation, and it's kind of one of my favorite scientific theories of all time because I think it's just absolutely ridiculous. And I know that I shouldn't make fun of people from this time period, but it just blows my mind. So preformation said that the sex cells contained this structure called the homunculus, which I have a difficult time saying, but anyways, there it is. And essentially what that is, is a miniature adult. It's just a little, little, I mean, like, just such tiny adult that will grow into a full human. So what it looked like is this is a drawing of sperm, and you can see right here, there's a little tiny person just, like, balled up inside, like, just sitting in there waiting to come out. And eventually, it keeps growing keeps growing and becomes a baby, which a full adult human. So this is what was believed at the time, and, you know, don't make fun of people, but dear goodness, this idea is a little ridiculous. But that's what they believed. It's kind of my favorite theory of all time. So the epigenesis was much closer, but, actually, most people at the time believed in the preformation over the epigenesis.
And then came Gregor Mendel, and I know all of you guys have heard about Mendel. He was this Austrian monk, and he began studying pea plants during the 1800. And so he was so crucial in providing us with the information that is genetics today. And so, at the time Mendel was studying, what people were believing in this idea of the Theory of Inherence, and this says that children were a blend of their parental traits. So, all the traits were kind of like fluids, and you mix them together, and that created the offspring. So it's kind of like paint. You mix red paint and white paint together, then the offspring would be the pink paint. You mix. And this is what was the major theory at the time Mendel was doing his research. But he actually ended up disproving this because he would mate purple pea plant flowers and white pea plant flowers, and they didn't turn into, like, a light purple. They were either purple or white. So there wasn't that mixing that the blending theory of inheritance predicted. So what Mendel did is he actually, after all of his studies, which we'll talk about a lot more, like, in just excruciating detail in future lessons, But he proposed that there were particles, not fluids, so it wasn't just like paint, that liquid paint, it was actual particles. And these particles controlled heredity. They controlled inheritance. And so today, we now know that these particles are called genes. At the time, they were called particles. And so he proposed a few things, and we're going to talk about more in detail these proposals in future topics. But he proposed that there are 2 copies of each particle, which we now know are called alleles, but I'll get into that in other videos. And each of these copies controls one trait, so for instance color, 2 copies of these particles control one color trait. And then he proposed that one is more dominant than the other, and the dominant one actually chooses what you see. So what you see here is it's kind of hard to see. You have a purple, and you have this, like, light pink one here, and I'm going to circle it in case you can't see it. So the blending theory of inheritance says that if you mix this purple ball with this light pink ball, what you'll get is this light purple one. But Mendel didn't see that. What he saw is that if you mate a purple with this light pink together, what you get is you either get purple or light pink. You don't get this blending. The blending theory, you know, couldn't be right. But, unfortunately, Mendel, like, he published his work in 1866, but generally was largely ignored and, pretty much forgotten about for about 40 years. And then in the 1900, there was this guy called William Bateson, and we'll talk about him more in the future. But, he, as well as some other scientists at the time, actually rediscovered Mendel's work, and they did an experiment and proved, you know, this guy wasn't just some, like, guy we forgot about. This stuff really means something, and this is when the term genetics was actually coined for the first time. And then you have this, another scientist, which we're going to talk about a lot more in the future, Thomas Hunt Morgan, Thomas H. Morgan, and he actually found, or really discovered more of the mechanism of how this works, how these how these particles or these genes were inherited, and he found that they were inherited on chromosomes. And he actually proposed the Chromosomal Theory of Inheritance in 1910. So these names I'm throwing out here, they you will need to know them and their dates and everything, but we're going to talk about them more in future topics. But for now, just know that this is kind of the step all the way from, you know, just domesticating dogs, light begets light, through preformation of the tiny human in the sperm, and then to Gregor Mendel, who was actually proven, and remembered and rediscovered in the 1900, and now we have, genetics today. So that's just a brief overview of the history of genetics, so now let's move on.
