Scientists studying the earth’s geological layers, have found that as they dig deeper, the further back in time they look, the simpler the fossilized organisms become. Life used to be simpler. But can life naturally arise from non-life?
I’m not talking about the Aristotelian notion of spontaneous generation that assumed putting rags and wheat in a jar would magically turn into mice when no one was looking. This was disproven in part by Fransisco Redi in the 1600’s and later by Louis Pasteur in the 1800’s. What we’re going to explore is the theory of abiogenesis. The theory that in the right circumstances, simple chemicals can naturally bond together to form organic molecules which organize themselves into living, evolving structures called cells.
Given a big enough time-span and enough generations, can we get from chemicals to humans? In order to answer that, we need to know what living organisms are made of.
Up until the 1800’s, there was a common misconception that life possessed some kind of vital force. This was different from the notion of a soul. It was believed that all living things possessed this force, and that organic material couldn’t be generated synthetically in a lab. Until in 1828, Freidrich Wohler did just that (synthesizing urea in a laboratory) – putting an end to the false notion of vitalism. Life is chemistry and all the energy that you run on comes from chemical reactions taking place in your body.
Since Wohler’s experiments, there have been many attempts to create entire living organisms in a lab. In the early 2000’s Martin Hanczyc and his team created simple protocells that moved around in a petri dish, responded to stimuli, sought out food, and underwent cell-splitting (similar to reproduction), but these were very simplistic and even lacked the DNA necessary to pass traits from one generation to the next. But in 2010 Craig Venter & his team were able to determine the minimal gene set for a viable cell, synthesized an artificial genome, and placed the DNA into a protocell that was able to reproduce using this synthetic DNA, demonstrating yet again that life is nothing but chemistry. But let’s dig deeper and get a closer look at what cells are actually made of.
Inside every living cell there are metabolic networks – networks of interactions between polymer complexes undergoing chemically regulated activities to keep the cell alive.
These polymer complexes are composed of macromolecules called polymers. And since “poly” means many, all these are is a collection of many monomers. Which are made up of organic molecules that you’re probably familiar with from chemistry class. In case this sound confusing, let me break it down for you.
There are four organic molecules found in every living organism: carbohydrates, lipids, nucleic acids, and proteins.
These are the building blocks of life, and every one of these building blocks is simply a different arrangement of atoms.
In the case of carbs, simple elements like hydrogen, oxygen, & carbon form simple sugars called monosaccharides which then make up more complex polysaccharides.
With lipids, simple elements, predominantly hydrogen, oxygen, and carbon form fatty acids and glycerol. These bond together to form triglycerides or fatty acids can bond with a simple phosphate group to make phospholipids.
With nucleic acids, hydrogen, oxygen, carbon, & nitrogen come together to form nucleotides which bond together to form nucleic acids.
And lastly, proteins: simple elements like hydrogen, oxygen, carbon, & nitrogen (and sometimes sulfur) make up amino acids which link together to make polypeptide chains.
Once you have these four building blocks for life they can work together, form various structures and play vital roles for every living organism. For example, when a poly-peptide chain gets long enough, these chains naturally fold into structures called proteins that carry out vital functions like speeding up chemical reactions, forming antibodies, and providing structural scaffolding.
The laws of physics are constant. If life can come from non-life we should be able to recreate physical simulations of early-earth-like environments and watch these steps (from simplicity to complexity) happen on their own. Now there very well may be several ways that life can arise naturally, so this wouldn’t necessarily tell us which simulations represent exactly how life came from non-life, but it would at least show us that it’s possible.
So what steps in this process have been observed in simulations? I’ll cover that in my next video. Until then, dare to be curious, but don’t drink the Koolaid!
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