Life

Cesare Emiliani, in his text, Planet Earth: Cosmology, Geology, and the Evolution of Life and Environment, says in his chapter on the origin of life:

“People are awed by life. Some call it “unique”. Many call it “a miracle”. All are puzzled and bewildered by it. Indeed, there is excellent cause for bewilderment – life, as we know it today, is the end product of 15 billion years of cosmic and terrestrial evolution and therefore is utterly complex. We see a fantastic machine with billions of moving parts, a machine that has been fine-tuned by nature to the utmost degree – and we are bewildered. I hope, however, that this book will convince you that, far from being a miracle, life is a necessary and inevitable consequence of the way the world originated and evolved. Indeed, the origin and evolution of life on Earth were foregone conclusions right from the beginning, given the mass, the chemical composition, and the physical and astronomical parameters of our planet.”

One blazing hot day on earth 4 billion years ago, after trillions of failed chemical experiments, in the rich soup of water and gases on primordial Earth[4], warmed by the sun and receiving energy from a violent lightning storm and from chemical interchanges, something utterly remarkable happened. The self-organizing powers of the processes on Earth came together to create the first life, an early replicating molecule that would be modified and shaped by evolutionary processes to eventually become the first prokaryotic (non-nucleated) cell (these were likely primitive viruses). Earth would never be the same again.

The process called mutation played an indispensible role in the development of life. One of the many life forms that appeared around 4 billion years ago was a cell that somehow discovered how to convert photons of light from the sun into energy. Capturing solar energy zipping into the cell at the speed of light, the cell was able to invent the biochemical machinery to convert nitrogen in the air into proteins for feeding itself. Modern-day animals (including humans) have still not mastered the trick of converting nitrogen in the air into the proteins required for their existence. We still rely on plants for this job. All mammalian food chains have plants at the bottom. Early plants flowered forth with many different forms, each tossed out into the great adventure to see what might come of them. They all entered existence.

An aside: The complexity of modern plants (they have over two times the number of genes as humans) continues to challenge the understanding of 21^st century science.

Now, the evolutionary processes then took a turn. Early blue-green bacteria satisfied their hydrogen needs from the waters of the oceans[5]. They cleaved a water molecule to produce hydrogen, releasing the oxygen into the atmosphere. Oxygen, one of the most reactive elements, transformed the primordial atmosphere, and disrupted the environment for the earliest life forms that had developed in the early atmosphere of ammonia, carbon monoxide, and hydrogen sulfide. In the next two billion years, the first cells either developed defense mechanisms against oxygen, learned to exploit it, or they became extinct, becoming a distant footnote in the relentless evolutionary course of life on Earth.

Ozone built up in the upper atmosphere, filtering out the most energetic rays from the Sun. Once again, the self-organizing patterns of creation played out their wondrous influences, and symbiotic cell life evolved. Interconnected life forms appeared and flourished in the shallow oceans, now protected from the killing ultraviolet rays of the Sun. The rhythms of life of these creatures had evolved to enmesh with each other as they shared the environment, each taking resources unneeded by the other, each providing an element to the environment required by the other.

About 1 billion years ago a cell invented sexual reproduction, a major step forward in the creation of new life forms. Sexual reproduction ensured that both mating cells will possess the advanced and defining characteristics of the lineage. This powerful preservation of lines of creativity led to the emergence of the multicellular organism, another major step toward the evolution of higher forms of life. Only 700 million years ago, the first multicellular animal appeared. (1)

Now we are almost 14 billion years from the springing forth, almost to our modern times. Dinosaurs flourished about 235 million years ago, and it was only 216 million years ago that the very first mammal appeared. Our recent ancestors, the monkeys, appeared 36 million years ago. The first humans, homo habilis, using stone tools, appeared about 2.6 million years ago[6]. Early forms of our species, homo sapiens, appeared a scant 200,000 years ago. Our language appeared about 40,000 years ago, and 18,000 years ago we left cave paintings in Europe.

We tamed dogs 10,000 years ago; tamed cattle 8,800 years ago, Sumeria in Mesopotamia arose about 7,000 years ago, and we settled Europe 5,000 years ago. About 3,000 years ago civilizations were arising along the Indus, Nile, and Tigris-Euphrates valleys, the time of our narrative creation story recited at the beginning of our time together this morning.