Origins of Life
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- This place sure is cool, but how did this all get here?
- Well earth wasn't always like this. It used to be an uninhabitable planet before life developed. Temperatures soared, asteroid impacts were commonplace, volcanic eruptions happened all the time... it all seems pretty bad, but it was actually really helpful to creating life on earth.
- What!? That stuff would just kill life, not help it. How would development even be possible?
- You see, inorganic molecules make up the abiotic world around us-everything that isn't living. However, these inorganic molecules can be used to make the inorganic molecules within living things. Those conditions that we think are extreme were actually the conditions that let those reactions take place!
- Okay so early Earth had a bunch of crazy things going on that made life, but how did we become a part of this?
- Humans are much more complex, multicellular organisms made of eukaryotic cells. Eukaryotic cells have specialized internal bodies called organelles, which are surrounded by a membrane and carry out specific functions-just like our organs!
- Great question! Humans obviously didn't live way back then, that was a whopping 4.5 billion years ago! Those first life forms I mentioned are prokaryotic, which are very simple, single celled organisms.
- Wait a minute! You said that we're made of eukaryotic cells, but all those cells back then were prokaryotic. How does that make any sense?
- That's cool and all, but what does this have to do with totally different types of cells?
- Those ancient prokaryotes had to eat just like you and I do. A lot of the time, they ate one another just like animals do today.
- Well, there's a theory called endosymbiosis that explains just that. According to the theory, one prokaryote tried to digest another by absorbing it through its membrane. However, the 'prey' prokaryote survived, and the two developed a symbiotic relationship. That means that their presence benefitted one another, and as they reproduced their offspring benefited too.
- That sounds super complicated. How do we even guess about how that happened?
- You see, inorganic molecules make up the abiotic world around us-everything that isn't living. However, these inorganic molecules can be used to make the inorganic molecules within living things. Those conditions that we think are extreme were actually the conditions that let those reactions take place!
- For example, eukaryotic cells today have organelles that are very similar to prokaryotic life. Organelles like mitochondria and chloroplasts have their own membranes, their own genetic material, reproduce like prokaryotes, and have very similar DNA sequencing.
- Well that's easy, there are cells everywhere, right? How do we know about life 4.5 billion years ago?
- The earliest eukaryotes came into existence around 2.7 billion years ago. But you do bring up a good point nonetheless. Things like fossil records and rock deposits tells us about earth's condition during that time.
- Groundbreaking experiments have been done too, such as the Stanley Miller experiment. Scientists such as Mr. Miller used inorganic molecules found on early earth and volatile conditions like electrical shocks to make organic molecules. They were essentially synthesizing early life in a lab!
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