Evolution: The Story of the Cell
By Tyler Woodward
In this article, we will talk about the idea of evolution and how we humans came to exist.
Table of Contents:
- A Sum of our Cells
- Evolutionary Theories
- Evolutionary History
- The Missing Piece
- The Human Genome Project
We often like to view evolution on the macro (large) scale, viewing how many species of plants, animals, insects, and fungi came to exist. But by doing this, we often overlook the micro-scale of how our cells have advanced over time, allowing these ever more complex organisms to come into existence. Just as all modern-humans have a common ancestor, so do our cells. The story of how these modern-day cells came into existence is interwoven into our story itself.
A Sum Of Our Cells:
We are just a sum of our cells. That is it. Every single action, emotion, or thought that we feel can be broken down to the cellular level. I think people often have a misconstrued idea of what the cell is and how it works, so to illustrate this point, I am going to steal Bruce Lipton’s analogy.
Our cells are like little people. Every cell is capable of performing all of the same functions as a person including:
- Respond to a stimulus
- Grow & Develop
- Maintain Homeostasis
- Process or metabolize energy
However, they do so on a much smaller scale. To understand the cell, we have to know at least a little bit about what the cell itself is made up of; we have organs, our cells have organelles. Here is a list of the main organelles in our cells, their functions and their human or “large scale” counterparts:
- Nucleus ≈ “Brain” - stores genetic information
- Cytoplasm ≈ Blood - intracellular fluid
- Mitochondria ≈ Heart - Site of metabolism
- Cellular Membrane ≈ Skin - regulates what enters & exits the cell
- Vacuole ≈ stomach - stores liquids
- Chloroplasts (plants) - photosynthesis occurs
- Cell Wall (plants) - provides rigid structure of plants via cellulose
But our cells did not always contain all of these “advanced” structures. To understand how modern-day cells came to exist, I think it is really useful to understand how modern-humans came to exist…
The History of Humans:
There are a few key events in human history that defined our evolution as a species.
- The “invention” of fire, allowed us to produce our own heat source and survive through cold spurs.
- Language provided us with the ability to communicate with each other and neighboring tribes.
- The agricultural revolution changed our society from a hunter-gatherer based society to an agricultural based one. We were no longer dependent on hunting to supply us with food, as we then had the ability to produce food for ourselves,
- Last, but not least, after the specialization of labor and developing more advanced farming techniques, every person in the group/tribe was no longer required to produce their own food. This opened up many opportunities for trading and development, establishing the world’s first economy. If you were not a great farmer, but were a phenomenal clothing maker or seamstress, you could now trade your clothes for food. This allowed for rapid progress as a society as individuals and families advanced within their trade, producing better products over time.
Here is the thing…
Just as humans became specialized, so did our cells
Which brings us to evolution...
There are two main theories which explain how evolution occurs:
- Darwin - Evolution by Natural Selection (Survival of the Fittest)
- Evolution by natural selection - Those that are best suited to survive are most likely to survive to adulthood and reproduce, passing down their genes onto the next generation.
- Ex. Moths & the Industrial Revolution
A famous example that illustrates survival of the fittest is the change seen moths in Great Britain during the industrial revolution. Prior to the industrial revolution, the majority of moths in Great Britain were white and blended into the trees, providing them with camouflage from predators (birds). During the industrial revolution due to smoke and soot, the trees in Great Britain turned blacked. This provided an advantage to the black moths already present in the moth population, as they now blended into the trees, where the white moths stood out. Over the course of 10 years, the black moth population skyrocketed, as the white moth population significantly declined because it was no longer advantageous, thus exemplary of survival of the fittest.
- Lamarck - Inheritance of acquired characteristics
- The theory of use & disuse - Organisms altered their behavior towards environmental change.
- Ex. Giraffes will continuously grow taller each generation if it is beneficial.
- Ex. Penguins lost their ability to fly over time because they stopped flying.
Lamarck’s theory has been pretty much disregarded. In the past, it did not really make any logical sense, especially when comparing it to Darwin’s theory and looking at evolution through the “macro” (large-scale) lens. But when you look at evolution through the “micro” lens or through the eyes of the cell and when you ask the right questions, the puzzle pieces begin to fall together.
So what is the right question?
Why? Why did life continually evolve? For what reason have “life forms” continually become more complex?
(This is going to a recurring theme throughout this article and I encourage you to keep asking yourself this question as you read)
If you are at all familiar with Earth’s history you may know that Earth has not always been the earth as we know it today. ‘Back in the day’, Earth was extremely hot and had very little, if any, oxygen in its atmosphere, which was made up of mostly carbon dioxide and nitrogen gases. We believe that about 3.8 billions years ago, in these conditions, the first cell was formed and used this anaerobic (lacking oxygen) environment to produce energy.
The first cells were very primitive in their structure consisting of a nuclear envelope (a less advanced version of the cellular membrane, remember cell membrane ~ skin of the cell) and RNA, the first genetic material. Over time, these cells advanced, developing new organelles like flagella (a whiplike structure used to propel the cell), more complex membrane proteins that allowed the cell to regulate what is able to enter/exit the cell and to help them better respond to and adapt to their environment, and finally DNA (a more stable version of RNA). These cells eventually evolved to be able to convert sunlight into energy through a process known as photosynthesis, marking a shift to Earth’s oxygen filled atmosphere as we know it today. This shift to an oxygenated atmosphere allowed for cells to develop methods of aerobic respiration (converting glucose or sugar and oxygen into carbon dioxide and water), as we humans perform today.
Eventually, as these cells continued to advance and grow, it is believed that a larger cell basically swallowed a smaller cell and these cells merged together (Endosymbiotic theory). The smaller cell continued to live within the bigger cell, producing energy for the bigger cell through either photosynthesis or cellular respiration, becoming the first chloroplasts and mitochondria respectively. These “merged” cells would become known as the first eukaryotic cells, the direct ancestors of our cells.
At some point down the line, these cells ran into an obstacle in that they could only grow so big. Remember, these cells have no means of “bulk flow”; there is no heart in these cells to pump oxygen or nutrients throughout the cell, meaning these cells relied solely on diffusion to get these nutrients. Diffusion is the movement of anything from high concentration to low concentration. Diffusion is the reason that when you make a bag of popcorn, the smell spreads throughout the whole room, when you put food coloring in a drink it naturally mixes throughout the drink, or when you open a door in the winter cold air rushes inside. The issue with diffusion is that it is slow. As cells increase in size, it takes more and more time for these nutrients to diffuse across the cell. Eventually, these cells reached a point in which they could not grow any bigger because they could not consume enough nutrients.
So these cells turned to their neighbors, developing more complex membrane proteins to communicate with nearby cells and their environment and regulate what can enter/exit the cell. These connections eventually turned into the first communities of living things and provided an active network of intercellular communication. This gave a huge advantage to these cells, as they could now receive significantly more information regarding their environment. These communities continued to grow over time from a few cells linked together to millions and eventually billions of cells. As these communities grew, it allowed these cells to work together instead of as individuals, distributing the workload across the community. Remember how humans began to specialize in certain tasks, making the community as a whole more efficient?
The Missing Piece:
We have been taught in biology that the nucleus of the cell is the human equivalent to our brain, but what if we have been looking at this backwards?
The central dogma or underlying belief of biology today is:
DNA → RNA → Proteins
DNA is our genetic code, which allows our cells to encode for/ produce proteins in the body. Basically, every three “pieces” of DNA encodes for one of twenty amino acids that are used commonly in the body. Hundreds of these amino acids are linked together to form a single protein. These twenty different amino acids allow for thousands of different proteins to be produced, performing various functions throughout the body. Proteins are like the “blue-collar workers” of the cell and are responsible for performing just about every task/function of the cell, including breaking down food, building immunity to foreign invaders, and facilitating growth and repair. Our nucleus contains this DNA which allows the cell to reproduce and to build these protein “workers”.
But how does the nucleus know which proteins to build?
For a long time we believed that, like our brain/nervous system, the cell’s nucleus was capable of regulating itself. However, in recent years, we have discovered that this is often not the case.
The Human Genome Project
In 1990, the US launched the Human Genome Project with the goal of identifying and mapping all of the genes within the human genome. At the time, scientists expected to find at least 120,000 genes, each encoding for a single protein in the body. They were shocked to find that the human genome was actually made up of less than 25,000 genes! This means that the majority of genes must encode for multiple proteins (not a 1:1 ratio). This also threw those scientists for a loop, as they could no longer justify our “advanced” genetics as the primary cause of our (human) complexity relative to other animals. To give you an idea of how stunned these scientists were at the time, yeast has about 5,000 genes and rice has about 38,000 genes. By this logic, we are about 4X as complex as yeast and half as complex as rice. We also discovered in this project that less than 2% of our DNA is regularly used to encode for the proteins found in our cells
So what is the purpose of the 98% non-coding DNA?
We have discovered in recent years that the remainder of DNA aka “Dark DNA” has three main functions:
- Regulating the production & assembly of the DNA-encoded proteins
- Responding to the environmental “information” to modify the activity of these protein-encoding genes
- Functioning as “gene” switches that are able to turn specific genes on/off and re-write DNA structure
Key Takeaway: About 98% of our genes are designed to respond to our environment.
The Story of the Cell:
For a long time, we have been missing this integral piece of piece of the biological puzzle. Since its discovery, we have believed that the nucleus was analogous to the brain of the cell, but in reality, the nucleus has much more in common with our genitals. Think about it, our genitals are responsible for the storage and transmission of genetic information. The cell’s nucleus is responsible for the storage and transcription of our DNA. Our genitals encode for our “babies” and our nuclei encode for our “proteins” and the replication of the cell. In fact, cells can survive for weeks after their nucleus has been removed.
The brain of the cell is much more similar to the cellular membrane. Our brain responds to external stimuli or our environment using our five senses and releasing hormones or electrical signals throughout the body as a response. Our cellular membrane is responsible for regulating the cell, determining what proteins are produced based on its external environment and determining what enters and exits the cell.
What does this mean?
It means that the story of evolution and our complexity is not found in our genetics, but rather in our cell’s ability to respond to its environment. This has stayed true from the first unicellular organisms to first communities of cells to the modern-day cells found in humans today. Think about every one of our biological systems: the skeletal system, muscular system, circulatory system, nervous system, etc., all start with a single cell. Hundreds or even thousands of these cells are grouped together to form tissues, which combine to form our organs and finally our organ systems. Ultimately, this results in the end-product, an organism.
The difference between us and these single cellular organisms is that we are capable of controlling our environment, including our external (macro) environment, the outside world, and our internal cellular environments. Only when you understand how to control your own environment can you truly understand what you are capable of and reach your potential.
Continued in “You are What you Choose to be”
My goal in writing this article, as always, is to provide you with logically-based principles that you can use to form your own conclusions regarding any information you may come across within this subject. I really hope you found this article interesting and if you have anything to add to this article, or any comments or criticism, feel free to reach out to me on our facebook groups (The Thermo Diet Community Group, The UMZU Community Group) or on Instagram @tylerwoodward__. Also, please feel free to share this article with anyone that might be interested.
Thanks for reading!
Until next time… be good
B.S. Physiology & Neurobiology