It is now thought that the universe began approximately 15 billion years ago, and that some 4.5 billion years ago the Earth was formed. No life existed on the planet during the early period after its formation.
With time, however, the atmosphere and environment became more suitable for the development of life. Simple substances gradually underwent a process of chemical evolution, forming compounds that were more and more complex. These eventually became the building blocks of life. The first living organisms, single-celled blue-green algae and bacteria, are thought to have appeared about 3.5 billion years ago. These simplest of life forms derived their energy from photosynthesis, a process whereby carbon dioxide and water combine in the presence of light to form the carbohydrates that power the cell’s metabolism.
The first multicellular organisms (hard-bodied animals like corals and starfish) arrived about 600 million years ago. It was only very recently in terms of these vast expanses of time, or about 100,000 years ago, that the first humans appeared. Thus an unfathomable span of time elapsed between the time of the Earth’s formation and the appearance of humankind.
It is estimated that the Earth is home to about 1.5 million distinct varieties of life. This number includes about 900,000 species of insects, 323,000 species of plants, 30,000 species of fish, 87,000 species of birds, and 77,000 different types of micro-organisms, not including viruses. If we consider the countless multitudes of other forms of life that exist on this planet, it becomes clear that even at a population of more than 5 billion, human life is a rare commodity.
Suppose it was equally possible for us to be born into this world as any one of the Earth’s countless inhabitants. If we were to divide a number even as large as 5 billion (Earth’s human population) by the vast number of all other individual living organisms on Earth, this would yield a very small number. In other words, we might say that the probability of being born a human being is extremely small.
The human being has been called the “final destination of evolution.” Regardless of the ultimate truth of this statement, it does suggest the magnificent power and potential that human life possesses, above and beyond that of other living beings. What makes human beings unique among other animals? Perhaps it is the function of the individual’s will to affect changes in himself and influence the environment. Life at each moment encompasses both body and spirit and both self and environment of all sentient beings – plants, sky and earth, on down to the most minute particles of dust. Life at each moment permeates the universe and is revealed in all phenomena.
We all have the potential to change ourselves for the better and influence others, our community and our environment in a healthy and positive way. We can therefore feel a profound sense of gratitude that we are able to possess the rare commodity called human life.