Chapter 9: Genes and Reproduction
The next question we have to answer is: How do genes get passed down from one generation to another?
Women create egg cells, and men create sperm cells. When a sperm meets an egg cell, the two join together to create a fertilized egg. That’s simple enough that I’m assuming you already know about it. If you don’t, I’m guessing any school teacher or university student could explain it to you.
You grow by creating new cells. Once an egg is fertilized, it splits into two cells.
Here we can talk about chemistry again. The chromosomes in the cell are really big molecules. You have other atoms in your cells. The chromosomes start a chemical reaction with some of the other atoms. That makes some of the other atoms in the cell turn into copies of the chromosomes.
When the fertilized egg splits into two cells, a copy of each chromosome goes into each cell. Then those cells each split in two and create four cells. And so on. This is how you grow from the time your mother gets pregnant up until you stop growing.
In the fertilized egg cell there are different chemicals in different parts of the cell. When the egg splits into two cells, each cell gets the same chromosomes, but each cell gets different amounts of the other chemicals in the cell. The different chemicals in each cell make different chemical reactions happen. That turns your cells into bone cells, muscle cells, skin cells, and all the other kinds of cells you have that make up the different parts of your body.
Over the course of your life, this keeps happening to you. Individual cells get old and die, but as long as you stay healthy, you keep replacing the old cells with new cells. If you build up muscles or get fat, you turn food molecules into new muscle cells or fat cells. If you get hungry and lose weight, you break up some of your cells to get the energy out of the molecules in them, and you don’t replace them as quickly. If you get sick, or when you get old, some of your cells die, and then you don’t replace them with new cells as quickly. Then you lose weight and you get weak.
When you make sperm or egg cells, a different chemical reaction happens, which makes those cells divide differently.
To create a sperm or egg cell, first all the chromosomes in a cell break up into genes. Then the genes mix together, join back together, and form new chromosomes.
Now the cell has 46 chromosomes in it, and all of the genes are yours. The chromosomes are different from any of the other chromosomes in the rest of your body though.
In the other cells in your body, you have 23 pairs of chromosomes. You got one of each pair from your father and the other from your mother. There are hundreds or thousands of genes in each chromosome.
When your chromosomes break up to form sperm or egg cells, some of the genes from one chromosome in a pair mix together with the genes from the other chromosome in the pair. The other genes from the two chromosomes join together to make another chromosome of the pair. Now you have a pair of chromosomes again, but now some of the genes on each chromosome came from your father, and some came from your mother.
Let’s say you had a pair of chromosomes for making your arm. On each of those chromosomes you have a gene for your fingers, one for your hand, one for your wrist, and so on. This isn’t really how genes and chromosomes work, but it’s the basic idea. This is another of those things that if you go study biology at the university you’ll have to learn the real version, but for farmers this is close enough.
When your genes divide up and create the new chromosomes, now you have two different chromosomes from the pair that made your arm. Now one of the chromosomes might have your father’s gene for fingers, your mother’s gene for hands, your father’s gene for wrists, your mother’s gene for your lower arms, and so on. The other chromosome in that pair would have your mother’s gene for fingers, your father’s gene for hands, your mother’s gene for wrists, your father’s gene for lower arms and so on. These are different from your original pair of chromosomes because in your original pair all the genes from your father were in the chromosome you got from your father, and all the genes you got from your mother were in the chromosome you got from your mother.
The chromosomes you got from your father were different from the chromosomes your father had, because when he created his sperm cells, his genes divided up and reformed new chromosomes in the same way. Some of the genes you got from your father came from his father, and some of the genes came from his mother, but now they were mixed together in the same chromosomes. And the same goes for the chromosomes you got from your mother.
Now that your mixed-up genes have joined together to create your 46 new chromosomes, your cell divides. Now one of each of the 23 pairs goes into each cell. Now you have two sperm cells or two egg cells that each carries 23 chromosomes. When a sperm cell meets up with an egg cell, they join and mix the chromosomes together. Now you have 23 pairs of chromosomes again in a fertilized egg.
I should say here that what’s known as the 23rd pair of chromosomes is the pair that determines the gender of the child. (It’s called the 23rd pair because biologists keep a list of the pairs of chromosomes so they can talk about which pair is which. The gender pair of chromosomes is the 23rd pair on the list.)
Some chromosomes are shaped like Xs and some are shaped like Ys. In the 23rd pair of chromosomes, there are actually two different kinds of chromosomes that can fit into that pair and work together. One is called the X chromosome and the other is called the Y chromosome. Men have an X and a Y chromosome. Women have two X chromosomes. That means that all of the eggs a woman creates carry X chromosomes. That also means that half of the sperms a man creates carry X chromosomes and the other half carry Y chromosomes. That means that if the sperm that fertilizes an egg carries an X chromosome, the fertilized egg has two X chromosomes, so it becomes a girl. If the sperm carries a Y chromosome, the fertilized egg becomes a boy. Whichever combination of chromosomes the fertilized egg gets for the 23rd pair start chemical reactions that create the head and face and body and arms and legs and everything else of a boy, or of a girl.
Now if we can say that you have a chromosome for your arm, and you have your mother’s finger genes and your father’s hand genes, you won’t end up with fingers exactly like your mother and hands exactly like your father. You end up with fingers like your mother and hands like your father, but your fingers and hands are either boy fingers and hands or girl fingers and hands, depending on which one you are. So if your mother had long fingers and your father had large hands, those are what you get, but you either get long boy fingers and large boy hands, or else you get long girl fingers and large girl hands.
This is an example of how lots of genes work together to create your body. Every part of your body is created by a lot of genes working together, instead of one gene for your fingers and one for your hands and so on. Someone who studied biology at a university could teach you more about that if you wanted, but that’s close enough for what I’m telling you about in this book.
Among a lot of animals, the males fight against each other to try to mate with females. This is another way that the strongest genes get passed down from generation to generation. The animals that have the strongest genes are the strongest animals, so they win the most fights, mate with the most females, have the most children, and pass the most of their alleles down to the next generation.
Men fight other men to mate with women a lot of times. Even when men don’t fight each other literally, they compete against each other to see who can build the best house and the best farm, or who can make the most money, or whatever. That’s the same competition animals have that keep their species healthy by passing the strongest alleles down from one generation to the next. That’s why competing against each other feels like such a good idea to a lot of men. Even though we have the same feelings most animals have when it comes to competing against each other, human intellect lets us compete differently. We still feel like it’s supposed to work the same way, but it doesn’t always. That can get us into trouble.
Men who are sickly can’t compete very well, so they can’t pass their alleles down to the next generation as well as healthy men, because healthy men have more time to find women, and have more time to do the things that attract women. However, when healthy men compete against each other, that doesn’t prove anything about who has the strongest genes. A farmer might have better alleles than a banker, because the farmer might be stronger than the banker and smarter than the banker. But if the banker has certain abilities, he can get a job that pays more money. If the banker’s parents had more money than the farmer’s parents, the banker probably went to the university and the farmer didn’t, so that’s another way the banker can make more money than the farmer. Now that the banker has more money than the farmer, he can buy more things than the farmer. That will help him attract more women because that will make him seem to have better alleles than the farmer. That will help him have more children, and that will help him pass more of his alleles down to the next generation, just like he wanted to do.
The banker can even use all his money to take the farmer’s farm. That’s another way the banker can compete against the farmer. When the banker owns the farmer’s farm, he has one more thing he can use to help him survive and help him attract women and have children. The farmer has one less thing he can use to help him survive, attract women, and have children.
This is a big problem that people who don’t understand much about biology are causing, which is causing problems all over the world. It’s really easy for people who take other people’s farms to say that the fact they were able to take the farmer’s farms proves the farmers were just stupid people, and get everyone else to believe them. So nobody else thinks anything of the farmers, and the people who are taking the farmers’ farms can keep right on taking their farms. That benefits a few people, but it harms a lot more people. It seems to a lot of people that the competition benefits the human race, but it doesn’t.
There aren’t any other species that can threaten us as a species anymore, so we don’t need a stronger species. What we need is a smarter species. Competition among people is spreading a lot of misery through the world. People have found a lot of ways to compete against other people. The whole purpose of military weapons is to help people compete against other people. Murder is a way people compete against each other. Theft is a way people compete against each other. Taking people’s land is a way people can compete against each other. War is a way people compete against each other. Slavery is a way people compete against each other. Any kind of oppression is a way that people compete against each other. But on the other hand, revolution is also a way people compete against each other.