How did we get from single celled organisms to all the diversity of life in the world today?
If you focus on how many differences there are between one species and another, you’ll be overwhelmed with information. But if you look at the critical differences between one species and another, suddenly it’s a coherent story. Now you’re looking at how few differences it took between one species and another to make all the rest of the differences evolve.
What had to change in those original cells to make the simplest plants evolve? Then the simplest animals? Then more complex animals?
ACT I
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3,500,000,000 years ago there were single celled organisms floating in the ocean. There are a lot of steps between them and us.
If you focus on how many differences there are between one species and another, you’ll be overwhelmed with information. But if you look at the critical differences between one species and another, suddenly it’s a coherent story. Now you’re looking at how few differences it took between one species and another to make all the rest of the differences evolve.
What had to change in those original cells to make the simplest plants evolve? Then the simplest animals? Then more complex animals?
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Genes are molecules that make copies of themselves, and that start other chemical reactions. Genes join together into chromosomes. They surround themselves with other molecules, to create their cell walls. Some of them are predators, which get the energy and molecules that continue their chemical reactions by breaking up other cells. Genes reproduce by making copies of themselves and dividing the cells in two.
The first genes in our story made copies of themselves directly when they came into contact with the right combinations of molecules and energy. But that’s not the only way for genes to make copies of themselves.
They could also make copies of themselves in a two-step process. They could come into contact with certain molecules, start a chemical reaction that produces new molecules, and then start a second chemical reaction with those molecules that creates a copy of themselves.
Or it could be three steps. The gene could start a chemical reaction that produces new molecules, some of those molecules could start a second chemical reaction with other molecules that produces new molecules, and the gene could start a third reaction with some of those molecules to create a copy of itself.
Or it could be a ten step process, or a hundred, or a million. It doesn’t matter how many steps it takes. As long as it starts with one gene and ends with more than one, that’s replication.
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At first, there were relatively few cells in the world. They spread around in the ocean currents and made more of themselves whenever they came into contact with the right combinations of molecules and energy. But eventually they reached a point where all the critical elements were tied up in the life cycles of cells. That’s when they ran into Finite = Finite.
When they reached the point where there wasn’t enough material for all the cells to keep making copies of themselves, how each species used energy and matter affected how much energy and matter the species would get.
Now the different species were competing for resources. The members of each species were competing for resources with each other also.
Now the differential survival rates of genes was making some individuals survive and reproduce, but not others. The combined effects of that made some species evolve and others go extinct.
Now we can say that the differential survival rates of genes depends on how efficiently they use their energy and atoms.
Genes are big molecules. The amino acids and proteins that genes form to create their cells are also big molecules.
Joining atoms together into big molecules depends on creating a lot of chemical bonds. Creating chemical bonds takes energy. That’s why life depends on energy.
Organisms that use their energy and matter more efficiently get higher survival rates. That means organisms evolve to use their energy and matter more efficiently.
ACT II
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The simplest types of cells— called prokaryotic cells— are made up of three basic things: the genes (connected in chromosomes), the cell wall, and cytoplasm, which is basically a stew of other chemicals inside the cell the that genes need to start their reactions.
Depending on the species of cell there can be other components that help with the life of the cell. The outside of the cell can have a sort of tail, called a flagellum, or can be covered in hairs, called cilia. Either of those can move to help the cell swim through the water or whatever it lives in.
The inside of the cell can have some organelles, meaning miniature organs. Those facilitate some of the chemical reactions that happen in the cell. The critical part of the life of a prokaryotic cell is that all the chemical reactions in the cell are started by the genes.
The sun dumps energy onto the Earth every day. Some prokaryotic cells evolved a very simple way of getting energy. Chlorophyll let them absorb sunlight. Those were algae, the first plants.
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Single-celled organisms come in different sizes. Eventually, some small organisms broke through the cell walls of larger organisms and invaded them.
Some were predators, which ate the larger organisms from the inside.
Some were parasites, which didn’t kill the larger organism directly, but drained energy and material from the larger organism to grow and make copies of themselves until the larger organism died.
But some settled into symbiotic relationships with the larger organisms, where they each produced something that was beneficial to the other. Like genes sticking together to form chromosomes, if one organism living inside another makes both of them survive and reproduce better than they did before, both of them have more offspring, and their offspring keep that relationship going.
Essentially, the small cells evolved into organelles inside the large cells. Those cells have much more complex lifecycles, which means they make more things happen over the course of their lives. Those additional things they do mean more opportunities for variations in characteristics and for the evolution of new traits.
Those are called eukaryotic cells. That’s what we have.
ACT III
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Eventually some cells divided but didn’t split apart. They stuck together and formed symbiotic relationships. Those were the first multicellular life forms.
The simplest symbiotic relationship for two predator cells would be for one of them to break up another cell to eat, and for the other to absorb some of the nutrients that otherwise would’ve floated away. That’s such a simple symbiotic relationship that more cells could be added to it.
Since these animals were evolving in the ocean, the ones who were in open water, as opposed to anchored to rocks, were floating. The evolution of movement began with the evolution of the ability to control how they floated. That’s what swimming is.
Single celled predators can move on their own. But whatever they use to swim grows out of their cell walls.
A few single celled predators stuck together could still do that pretty well. But every time two cells stick together, it reduces the surface area of their cell walls they have available for propulsion.
For an organism to grow much bigger than a few cells, it would need to evolve a new way to move. Some of these multicellular predators evolved the ability to shift the positions of their cells in relation to each other. That’s what you’d call wiggling.
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Now think about how much organization that would take.
For a multicellular organism to coordinate its cells to move in a way that propels it toward food, it needs several things.
First, it needs to detect food. It could react to chemicals that a food source gave off and swim toward it. Single celled predators all do that.
But if single celled predators that were all stuck together all detected the food at the same time, and all started moving toward it at the same time, they wouldn’t be helping each other move. So they’d move slower than if they were all swimming individually.
If one of them broke loose and started swimming on its own, it would get to the food first. That would lower the survival rate of the multicellular organism.
If one of the cells got a variation that made it recognize food more easily than the others, it would start moving first. Would that be enough to make the others start swimming in the same direction? Or would they wait until they detected the food to start moving toward it? Either way, the one that detected it and started moving toward it first is now the front of the organism.
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Now another variation would help it move faster. If the food detection cell detected the food long before the others, and it started a chemical reaction when it did, and that chemical reaction created chemicals that the other cells recognized, andthat made them start moving toward the food, essentially the food detection cell would be sending a message, or a signal, to the other cells.
Once this organism had one cell that could detect food first and signal the other cells which direction it was, the other cells wouldn’t need to detect food at all anymore. That would also let the food detection cell get better at detecting food, now that it didn’t have to wait for the other cells to detect it to be able to move toward it. That raised the survival rate of the organisms that could do it, so that evolved.
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Now think back to the story of electro-strong-weak force. Electromagnetism is the force that attracts electrons to the nuclei of atoms. Chemical reactions shift electrons among atoms. That means that every chemical reaction has an electrical current.
Some types of atoms, meaning some chemical elements, conduct electricity faster than others. That’s why wires are made of metal and they’re insulated with rubber. Out of all the chemical elements in those original cells, some of them conducted electricity faster than the others.
Electricity can move faster than chemical reactions happen. That’s why it’s faster to turn on a light switch than it is to snap and shake up a glow stick. That means the fastest way for a food sensor cell to send a signal to the other cells would be electrically.
If the food sensor cell started a chemical reaction when it encountered traces of food, and that chemical reaction was connected to molecules that conducted electricity easily, which ran through all the other cells and made them move, it would only take one chemical reaction to get all the cells moving, instead of one chemical reaction for each cell. Organisms that could send their food detection signals faster got higher survival rates, so that evolved.
Now this multicellular life form has an area of its body that takes in information, starts chemical reactions, and sends electrical signals to the rest of the body to make it move. That’s what a brain is.
ACT IV
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Since these multicellular life forms were moving through water, a streamlined shape would let them move fastest and would require the least energy. That increased the survival rates of organisms, so that evolved.
The most effective way for a long, narrow organism to swim through the water and absorb nutrients would be for the cells to form a tube that could surround a piece of food and contain all of its nutrients.
A tube-shaped animal that swallows food, digests it, and expels the waste is what a worm is.
That basic body style created more opportunities for variations to adapt it to different living conditions, different ways of moving, different ways of processing information, and different ways of getting food. You and every other animal species that has a digestive system is a more complicated version of a worm.
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Here’s an experiment you can try.
Get down on your hands and knees. Now try crawling forwards, sideways, and backwards.
Now think about which direction your mouth is pointing in relation to the direction you crawl fastest. It’s in the front of your body.
Think about where your brain is. It’s in the front of your body.
Think about where your eyes, your ears, your nose, and your tongue are. Also in the front of your body.
That’s where every other animal’s mouth, brain, eyes, ears, nose, and tongue are.
ACT V
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Now I’m going to jump ahead a lot more steps.
The fish that we’re most accustomed to seeing, because they’re the ones that are sold most in pet stores and grocery stores, are deep water fish. They move through water easily because their bodies are wide in one direction and narrow in the other. That lets them bend in the narrow direction to help them swim.
Deep water fish are narrow side to side and wide top to bottom. But fish that live near the bottoms of bodies of water are different from that. Some are wide side to side and narrow top to bottom. Some are more round.
Either of those lets them hug the seabed or riverbed more closely. It also lets them live in shallower water.
Fish have fins that help them swim. Deep water fish can move their fins to change the way water flows around them, or flap their fins to help propel themselves. But bottom feeder fish could also use their fins to drag themselves along river beds.
Fish that lived in shallow water would use their fins to do that a lot. That means variations that made them better at dragging themselves over riverbeds would get a higher survival rate.
Fish breathe by taking oxygen out of the water with their gills.
Some fish also have ballast sacks that help them swim. Those are organs they can fill with air to help them float. They swim up to the surface and suck in air with their mouths. The air in their ballast sacks helps them float around near the surface. Then when they want to dive they expel the air.
As you can imagine, eventually a variation connected the gills of some fish to their ballast sacks and let them take oxygen out of the air they sucked in. That’s what lungs are.
Bottom feeder fish with lungs, who can use their fins to drag themselves along the beds of shallow rivers, can also crawl up out of the water and onto land. And if they find new food sources there, that increases their survival rate again.
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Variations that made fish better at living on land let them spend more time on land. Eventually some of these fish evolved to a point where they depended on living partly in the water and partly on land.
That’s not a fish anymore. That’s an amphibian.
Eventually some amphibians got so good at living on land they stayed there all the time, or almost all the time, even though some of them still lived near the water and spent a lot of time swimming in it.
That’s not an amphibian anymore. That’s a reptile.
ACT VI
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What does this tell us about how evolution fits into the four mathematical laws? There are two ways it does.
Evolution is always an interaction between the members of a species and their environment.
Evolution is the product of replication, variation, and selection. Parents have multiple offspring; the offspring have different characteristics; and the offspring whose characteristics are the best match to the environment tend to be the ones that survive and reproduce the most.
When an environment changes, or a species moves into a new environment, the environmental pressures change. The new environmental pressures favor new variations. That lets new characteristics take hold, and makes some existing characteristics more common and others less common.
If those new conditions last long enough, some of the new characteristics turn into traits and the old species evolves into a new species. That makes evolution part of Change = Motion.
When an environment stays stable, it means that the environmental pressures stay the same. New environmental pressures don’t appear. That means the old environmental pressures continue to favor the existing characteristics and traits of the species.
Variation and selection still happen. But since the species has already been evolving to fit that environment for many generations, the new variations are a worse fit to the environment. That gives them lower survival rates, so they’re the ones that die out.
New characteristics don’t last, existing characteristics don’t become more or less common, and the traits of the species don’t change. The species stays the same. It doesn’t evolve into a new species.
That’s a number of factors balancing each other out. That’s Balance = Stability.
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Replication could also be called dispersal. The genes that started in two parents spread into offspring.
Variation could also be called diversification. Two combinations of genes turned into more than two combinations of genes.
Selection could also be called destruction. In the wild, most of the offspring of every species turns into food for something else before they reproduce. Up until a few thousand years ago that was true for us too. We’ve outsmarted death in a lot of ways. That’s how we got into our population explosion.
Replication, variation, and selection, or dispersal, diversification, and destruction, are each a way that things move from high concentration to low concentration more than they move from low concentration to high concentration.
If two rabbits have eight babies, it means two combinations of genes created eight more combinations of genes, and they’re all different from each other.
Then if six of the baby rabbits get eaten by predators, it means most of those combinations of genes break up.
That means that evolution is caused by three manifestations of the Second Law of Thermodynamics running into each other. Or as I’ve been calling it here, three forms of Change = Motion.