You and I have something fundamental in common. We are both ALIVE. We also both surrounded by an uncountable variety and quantity of living forms. Scoop up a clump of dirt, and you are likely carrying more bacteria than there are humans on planet Earth.
Because bacteria are so abundant, ubiquitous, and invisible to the human eye, biologist E.O. Wilson often refers to them as the “dark matter of the biosphere”.
But where did all this life come from?
Before we can answer that we need to figure out what life is. Besides being bizarre, many scientists describe life as an open system that constantly extracts energy from its environment in order to maintain its own internal processes. We call this complex maintenance a metabolism.
How does life manage to do this?
With something biologist Leslie Orgel called “specified complexity”. Life has a biological memory of its own environment encoded in highly ordered molecules. On our island of life, all that information is encoded in the same basic code: deoxyribonucleic acid; better known as DNA.
Then life does something else interesting. Life reproduces its own information; and as a result of differential survival, life changes over time in a symbiotic way with the environment, or it perishes.
But when did it first start to occur on Earth?
To find out, we need to go back 4 billion years, to the early Earth. When the Earth first formed, it looked nothing like it does today. The moon was much closer, there was no water, and most importantly, there was no life. There was geology, there was chemistry, but there was no biology.
Numerous fossilized biological microstructures from Australia, dating to 3.5 billion years ago suggests that this situation changed rapidly. Somehow, the Earth had started teeming with primitive life. What was going on?
Well, abiogenesis was going on, the natural process where biology emerges from chemistry. And it was going on in a very chaotic environment.
Earth weathered the Late Heavy Bombardment, a period of meteor and asteroid collisions, that occurred 100 times higher than the contemporary average.
To a life-filled planet, this bombardment would have been catastrophic. But to a life-less planet, this planet brought gifts, including water and organic compounds; critical ingredients for life as we know it.
The Earth now had oceans, and those oceans were filled with complex chemistry. But how did these ingredients spontaneously self-organize, into the complex biological structures we find in every cell today.
Back in the present day, abiogenesis has proven to be one of the biggest mysteries for modern scientists. This mystery runs so deep that microbiologist Lynn Margulis said: “to go from a bacterium to people, is less of a step, than to go from a mixture of amino acids to a bacterium.”
Biologists like Jack Szostak are trying to take that step, by producing simple chemical systems that can transition into systems exhibiting life-like characteristics. The result would be revealing a scientific “holy grail”: understanding the pathway (or pathways) to life.
Experimentation has shown us that it’s really hard to replicate abiogenesis. But they have also revealed fascinating hints about the pathway to biology. Some organic molecules naturally develop water-loving and water-hating membranes. This allows for something essential for cellular activity: compartmentalization of amino acids and nucleotides, the building blocks of protein, RNA, and DNA. And consequently, a potential first step towards a proto-cell with the biological machinery necessary for cellular growth and reproduction.
While we have yet to uncover exactly how this pathway was achieved, what we do know is that once the genetic code for life emerged on Earth, those first living forms shared their genes as liberally as humans share ideas globally today.
By sharing biological information, early life developed useful adaptations, allowing them to persist through supervolcanoes, asteroids, and global ice ages. So although life is mysterious, it is also most definitely resilient.
Remember that clump of dirt I was holding with billions of bacteria? Our life-filled world stemmed from microscopic pioneers that shared a lot in common with these extant bacteria.
This simple life also makes me wonder. Is our pale blue dot unique in it’s ability to foster abiogenesis. Or is it a simple and common process throughout the universe?
I’ll be in the comments, so discuss this with my below!