The Evolution of Primitive Earth
The beautiful image of Earth as seen from the moon, a blue and white sphere hanging in black space, changed our self-understanding in a deep way. We went from a perspective which saw the natural world as a kind of platform created for our exploitation to another which appreciated the planet as a whole, with us humans as simply an interrelated part of the larger web of life. But Earth was not always that way. It took a series of dramatic changes to evolve the blue planet we know today.
Our planet formed about four billion years ago, rather late in the universe’s over thirteen-billion-year history, at the same time as our sun was being formed from the coalescing debris of a huge exploding supernova. The supernova had “cooked up” in million-degree processes the higher elements, so the building blocks of future life on Earth were already present in the clouds of debris. As the forming sun turned on its axis, the debris turned with it, the whole flattening out like a big pancake. Soon small clusters began to form in the cloud of debris and these centers of gravitational pull attracted material to themselves, growing eventually into planets.
The four outermost planets, Jupiter, Saturn, Uranus and Neptune are huge, with diameters ranging from four to ten times that of Earth, and also cold, ranging from 200 to 300 degrees below zero F. Their atmospheres consist mostly of hydrogen gas, reflecting the composition of the universe as a whole. There’s no room for life to develop here.
The innermost planet, Mercury, about a third the size of Earth, has no atmosphere to speak of. Spinning slowly, taking almost 60 Earth days for a single rotation, the sunbaked side can reach temperatures as high as 800 degrees F, while the dark side may fall to almost 300 degrees below zero—not hospitable to life.
Venus and Mars, Earth’s sister planets, have characteristics similar to Earth, so life could have developed there. Venus, particularly, showed promise, but unfortunately fell victim to the greenhouse effect and global warming, its temperature rising to about 900 degrees F. Mars is still a candidate for some form of primitive life, and investigation continues. So Earth is the only planet in our solar system where conditions are just right.
As the newly-formed planet cooled, a heavy iron-rich core formed, surrounded by a solid mantle and a thin crust. The initial atmosphere was mostly hydrogen, like the rest of the universe. Earth’s gravitational pull was not strong enough to hold this lightest of elements, and most of the hydrogen drifted away. Some reacted with other elements to form hydrogen-rich compounds like methane (CH4) and ammonia (NH3). There was none of the oxygen essential to life as we know it, and water, the indispensable condition for life, was mostly trapped within the rocky mantle. With time volcanic activity released some of the water in the form of vapor.
During this period, there were a number of smaller “planetoids” orbiting the sun and some of these bombarded the forming Earth over millions of years. The result was a sweeping away of some of the surface and atmosphere,
making the process of formation more complex. One of the largest of these collisions is thought to have resulted in the formation of Earth’s moon.
As Earth continued to cool, the water vapor began to condense into liquid, and years and years of torrential rain began, eventually forming the seas which cover over two-thirds of the surface of our planet. As water evaporated from the surface and returned to the atmosphere, it joined the rainfall, and the hydrological cycle was born.
The earliest forms of life originated in the oceans. At this time there was not yet an ozone layer, that modern miracle which protects us from most of the harmful ultraviolet light, so the oceans were continuously bombarded with this high-energy form of electromagnetic radiation. It was radiation strong enough to break and reform carbon bonds, in principle able to produce organic molecules essential to life such as amino acids and nucleic acids.
In a landmark experiment at the University of Chicago in 1957, a sealed container of water and primitive-earth-like gases was subjected to continuous electric discharge for a week. From the product, the investigators were able to isolate some amino acids and nucleic acids. It was concluded that primitive earth conditions could lead to spontaneous formation of the basic molecules necessary for life.
Here the conundrum arises, a “chicken or egg” question. Proteins cannot form from amino acids without the DNA template to code the sequence properly. Functioning of the DNA requires enzymes, forms of protein. Neither can work without the other. So how does it begin?
In desperation, some have suggested that the seeding of life came from outer space. Certain meteors, in fact, have been found to contain organic molecules similar to those found in living organisms. While this may be a solution to the immediate problem, it just pushes the question back one step: How did life arise in the place where the meteor came from?
A Teilhardian view would propose a different perspective. Suppose we are dealing not with individual molecules acting independently, but rather with the universe acting as a whole. The divine presence acting within the evolutionary process would be directing it along to its ultimate goal, not only life, but self-reflective consciousness raised to its highest level.
It has all been gift to us. As if aware that we would be coming along later, all has been prepared, often in surprising and even miraculous ways. Our response can only be gratitude.
But we are not there yet. Let’s help the process along, raising our own consciousness, cultivating peace in our own hearts and working to create conditions for peace in the world. The future is in our hands. What a privilege!
Dom Roberti Dom Roberti, PhD, is a member of CPF
