Prominent researchers and scientists from around the world will tell you that humans evolved from single-celled organisms. But if you’ve ever wanted to take a deeper dive into how something so small could lead to something so big – an estimated 7.9 billion people, to be specific – keep reading. We’ll explain what led to the origin of mitochondria, how early cells evolved into complex cells and the important role that symbiosis has played in cell evolution.
Which cells came first on earth?
Every living thing can be traced back to the first cell on earth: a single-celled microorganism called a prokaryotic cell. Prokaryotic cells are thought to have originated on earth following a series of events that combined several organic compounds with the right environmental factors. While we can’t know for sure that prokaryotic cells were the first cells on earth, several experiments have led scientists to believe that this is the case.
“Prokaryotic cells are single-celled organisms that fall under two domains: bacteria and archaea”, explains MitoQ’s Research and Development Project Manager, Kai Man Yuen. “The first cells would have likely been primitive prokaryotic cells which may have only had organic compounds such as RNA surrounded by a membrane. Based on fossil evidence, prokaryotes appeared on Earth 3.5 to 3.8 billion years ago - making them the first inhabitants on Earth.”
How did humans evolve from a single cell?
Scientists believe eukaryotic cells – the cells humans are made from - evolved from prokaryotic cells around two billion years ago. Because prokaryotic cells are single-celled microorganisms, they’re not capable of creating complex creatures – like humans – on their own. For complex species to exist, there need to be multicellular organisms that can carry out an array of functions.
The theory is that symbiosis – the process when two different organisms interact - led to the evolution of eukaryotic cells. Because eukaryotic cells can be multicellular, it became possible for complex beings to emerge. Theorists also believe that a similar symbiosis occurred between eukaryotic cells and bacteria, resulting in your mitochondria: the powerhouses that give your cells the energy to function.
“Mitochondria have always been known as the powerhouse of the cell, but that is not doing justice to what they can do”, adds Kai Man. “While they do provide energy for processes in life forms, they also help with regulation in the body along with helping other systems in your body, like the immune system.”
Of course, it took a long time for multicellular organisms to evolve into humans (initially, there wasn’t enough oxygen on the planet to sustain human life). One of the first known multicellular animals was a poriferan, also known as a sponge (not the kind you use to wipe down your kitchen bench). Poriferans are fascinating aquatic invertebrates whose cells can shift dramatically, allowing the invertebrates to change shape. It’s suspected that, by eating certain bacteria, these creatures may have made a small contribution towards creating more oxygen - making the earth inhabitable for human life.
What is the Cambrian explosion and why is it important?
Because cells work better when they’re together, multi-cellular organisms continued to evolve – which eventually led to what is now known as the “Cambrian explosion”. It’s estimated that 541-485 million years ago there was an “explosion” of new species on earth. New inhabitants of different shapes, sizes and ways of consuming energy began roaming the earth, and our current food ecosystem began to form.
Now, some 541 – 485 million years later, you need only look in the mirror to see how far cells have evolved from there. What began as one, single-celled organism, led to you: a person made of trillions of cells that have many different functions. Some form your body and organs, some protect your immune system – and some make it possible for you to create new life!
Take care of your cells. They make it possible for you to move, breathe, function and exist.
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