In the Beginning
In the beginning... there was a singularity. Physicists tell us that the universe, as we know it, began between 10 and 20 billion years ago, at a moment in time they call the Big Bang. Our own star is comparatively young. Estimates are that it formed about 5 billion years ago. As our solar system was forming, cosmic dust gradually got swept up and began to form planets. Scientists estimate that our own planet reached its present size at about 4.6 billion years ago. That is generally taken as the age of the planet Earth.
In the beginning, planet Earth was a really miserable place. The way that the planet was formed, with ever larger and larger chunks of material slamming into it, created an enormous amount of heat. When the planet first formed it was melted. It was no place where one could ever conceive of life existing. Less than a billion years later, however, the fossil record clearly shows that life was there. This life was in the form of simple cells that resembled the bacteria we see around us today.
This is pretty fast work, especially when you consider that it took about a half a billion years just for the Earth to cool enough to actually have rocks and an atmosphere. In fact, some scientists now argue, based on fossil evidence, that life might have been present even earlier, as earlier as four billion years ago.
What we can take from this is that life appeared on the planet almost as soon as it was possible to do so. As soon as there were rocks to record the existence of life, we find evidence that life is there.
Where do these organisms come from?
In the beggining, life originated on the early Earth from non-living materials. All of the diverse forms of life we see around us today have arisen from some common, primitive, single original living entity. This is pretty deep stuff, a very cool idea.
There are alternatives to this account, of course. Many religious faiths hold that, in the beginning, life was bestowed on the planet by the work of a deity, but this is a pretty boring idea. Another alternative, one that has been suggested repeatedly over the years by a number of scientists, is the panspermia hypothesis. It suggests that the first life on Earth came from somewhere else in space.
Both of these alternatives, however, beg the question of how living matter could arise from non-living matter. That brings an important question into the table.
What’s the minimal difference between living and non-living materials? This is basically the same as asking “what is life?”. This question has been around for a long time. For me, however, with all the knowledge we have today at our disposal, to address this question is pretty simple.
So, what is life?
Life is defined by what is called organic chemistry. The most fundamental difference between living and non-living matter has to do with chemistry. Living things all have in common the fact that they are made of a particular class of chemical compounds. These are compounds that are built around the unique chemical properties of the element carbon. These kinds of compounds are called organic compounds. They are called that way because they are uniquely associated with living organic things.
There are only four kinds of organic compounds, broadly speaking. The first kind are amino-acids. These are the things that make up protein. The second kind of organic compound are the nucleic acids. These nucleic acids are DNA and RNA. The third class are the carbohydrates. These are what we commonly call sugars. The last general class of organic compounds are the lipids. Lipids are what we commonly call fats in many cases, but lipids can actually take a number of different forms.
These organic compounds have particular and quite sophisticated chemical properties that are unique to them. There is one property that is particularly remarkable, that is that the complex organic compounds that we find on the planet today, the stuff we are made of, is generally only produced through the action of living things. Another way to put this is that the creation of new organic matters depends on the existence of organic matter. You can’t make more organic compounds unless you got compounds to make them.
We can be quite confident given what we know about how the planet was formed the early Earth was entirely inorganic. Then, we have to ask: Where did the organic compounds that life depends on came from in the beginning? At this point, you might think that I’m going to throw Intelligent Design and Creationist arguments at you. I won’t, don’t worry. I’ll create some tension and leave that question unanswered, until next time, when we talk about the exciting, random and unintelligent origin of life.
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