Via listverse.com by Brian Molinari
Whether we refer to the act of living or to all sentient beings in this world, life has always been a difficult concept for humans to understand. Even when life has preceded us on this planet for 3.5 billion years—and we ourselves have roamed Earth for plenty of millennia—there are many questions about it that we still cannot answer. What is the meaning of life? Is there life after death? These, among many others, are typical questions of any philosophical debate, questions as old as humankind itself.
[1] But then we have strange questions, unconventional doubts about life that do not usually come to our minds on a normal day. Have you ever wondered what
Earth would be like if it were devoid of all life? Then this article is for you. If not, keep reading anyway; some of the answers, or the questions themselves, exposed here will certainly not leave you indifferent.
10. How Much Life Has Ever Existed? Currently, the human population is slowly approaching eight billion people. That is certainly quite a number, but it does not even compare with the 100 trillion ants under our feet. And it is estimated that, at any given time, there are five nonillion bacteria in the world—that’s a “5” followed by 30 zeros. There is no doubt that there are so many living organisms on Earth that trying to count them all would be an unachievable task. And again, all this is just about the currently existing
life-forms. But what about all the life that has existed in the past?
Determining how many creatures could have inhabited Earth throughout the history of the planet is extremely difficult. It is believed that complex life has been around in this world for at least 570 million years. And the fossils we have managed to recover are a minimum percentage compared to the prehistoric remains that are either out of our reach or have been destroyed by geological processes. But using their ingenuity, scientists have come up with a correlation between the number of fossils and the currently known species to estimate the total of life that has ever existed. Today, the experts are pretty convinced that 99.9 percent of all species on Earth are extinct.
This number is understandable, considering that the Earth’s biosphere has suffered five
mass extinctions during the last 400 million years. On average, more than 80 percent of all living beings were erased from the face of the Earth in each of these five events. And a significant part of the scientific community believes that today, we are facing a sixth mass extinction. Estimates say that species disappear 100 times faster today than before our existence, and in the last 50 years, humans have eliminated 60 percent of animal life. So, unfortunately for us, death is much more common than life in this world.
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9. Is Life On Earth Of Alien Origin? Today, most scientists are sure that all life on Earth comes from a common ancestor. This primal being would have been nothing more than a unicellular organism, created by random chemical reactions in the early Earth. However, what scientists do not yet understand is exactly how these processes took place. And all their attempts to replicate the origin of life have failed so far. Perhaps the answer to this mystery could be found in a theory called lithopanspermia.
The theory of panspermia suggests that early life-forms were brought to Earth from somewhere else in the
universe, such as nearby planets. Within the same idea, lithopanspermia states that rocky fragments of another world containing microbial life were ejected into space after some kind of planetary impact. Millions of years later, those rocks reached Earth, and the life they carried inside began its evolutionary cycle here. The concept behind panspermia appeared several centuries ago in France, and since then, it has been an object of scientific study, although other theories generate more interest nowadays.
Nevertheless, there are several indications supporting the possibility that lithopanspermia really occurred. Using collision simulations, researchers at Pennsylvania State University have concluded that it is statistically possible that a space rock containing microbes can travel from one planet to another by ejection.
[3] Of course, there is the problem that space is too hostile to allow the survival of life, due to factors such as radiation and extreme temperatures. But we know that there are multiple bacterial species capable of
resisting the harshest environments, from the hottest places on Earth to the nothingness of outer space.
In addition, a recent study shows that the main elements that make up life on Earth are common in stars, existing more abundantly toward the center of our galaxy than in our planetary region. In short, the matter we are formed from literally comes from another region of the universe. So life may not be so special across the cosmos after all.