We live in a universe where matter is distributed in a hundred billion galaxies, each containing a hundred billion stars, made up of particles, such as electrons and protons, or as waves or quantum strings. Tucked into the 14-billion-year history of this vast observable universe with 100 trillion planets is a pale blue dot teeming with life and a technological civilization composed of a strange species known as homo sapiens.
Are we an aberration, an evolutionary accident, or are we one of millions of evolving beings scattered throughout the distant reaches of the cosmos? In June of 2016, The New York Times attempted to answer this great unanswered question of the human species, publishing an op-ed titled, “Yes, There Have Been Aliens.”
In a brilliant display of intuition versus evidence, astrophysicist Adam Frank at the University of Rochester and author of “Light of the Stars: Alien Worlds and the Fate of the Earth”, proposed that “while we do not know if any advanced extraterrestrial civilizations currently exist in our galaxy, extraterrestrial civilizations almost certainly existed at one time or another in the evolution of the cosmos. The degree of pessimism required to doubt the existence, at some point in time, of an advanced extraterrestrial civilization borders on the irrational. We now have enough information to conclude that they almost certainly existed at some point in cosmic history.”
The pessimism line actually represents the 10 billion trillion times the universe has run its experiment with planets and life.”
Frank writes that this probability is not an abstraction, not just a pure number. Instead, he says, it represents something very real: “10 billion trillion planets existing in the right place for nature to have at it. Each world is a place where winds may blow over mountains, where mists may rise in valleys, where seas may churn and rivers may flow. (Note our solar system has two worlds in the Goldilocks zone — Earth and Mars — and both have had winds, seas and rivers). When you hold that image in your mind, you see something remarkable: The pessimism line actually represents the 10 billion trillion times the universe has run its experiment with planets and life.”
Frank’s argument have their appeal, countered Ross Andersen in The Atlantic, but it is an appeal to intuition: “The simple fact is that no matter how much we wish to live in a universe that teems with life—and many of us wish quite fervently—we haven’t the slightest clue how often it evolves. Indeed, we aren’t even sure how life arose on this planet. We have our just-so stories about lightning strikes and volcanic vents, but no one has come close to duplicating abiogenesis in a lab. Nor do we know whether basic organisms reliably evolve into beings like us.”
Evolutionary biologist Wentao Ma and collaborators, observes Frank, used computer simulations to show that the first replicating molecules could have been short strands of RNA that were easy to form and which quickly led to a “takeover” by DNA. And, as neurobiologist and leading expert on evolution of intelligence, Lori Marino has argued, human intelligence evolved on top of cognitive structures that already had a long history of life on Earth. Thus our kind of intelligence should no longer be seen as entirely separated from what evolved before.
We are a genetic Accident
For what purpose did the human brain evolve is a question that has puzzled scientists for decades, and was answered in 2010 by Colin Blakemore, an Oxford neurobiologist who argued that a mutation in the brain of a single human being 200,000 years ago turned intellectually able primates into a super-intelligent species that would conquer the world. Homo sapiens appears to be a genetic accident.
We are the only species of the billions of species that have existed on Earth that has shown an aptitude for radios and even we failed to build one during the first 99% of our 7 million year history, according to Australia National University’s Charles Lineweaver.
Mutation in the Brain of Mitochondrial Eve
Genetic studies suggest every living human can be traced back to a single woman called “Mitochondrial Eve” who lived about 200,000 years ago, Blakemore said in an interview with The Guardian. He suggested that “the sudden expansion of the brain 200,000 years ago was a dramatic spontaneous mutation in the brain of Mitochondrial Eve or a relative which then spread through the species. A change in a single gene would have been enough.”
Blakemore stressed that the plasticity that our brains were enhanced with when this mutation occurred. Some scientists, he pointed out, “believe that skills like language have a strong genetic basis, but my theory stresses the opposite, that knowledge, picked up by our now powerful brains, is the crucial mental component. It means that we are uniquely gifted in our ability to learn from experience and to pass this on to future generations.”
The huge and logical downside to Blakemore’s theory is that with a single generation starved of knowledge, thanks to some mass extinction global disaster, for example, would be cast back to the Stone Age. Blakemore observes, “Everything would be undone. On the other hand, there is no sign that the human brain has reached its capacity to accumulate knowledge, which means that the wonders we have already created – from spaceships to computers – represent only the start of our achievements.”
The universe gets to run the experiment many, many times. So if you want to argue Earth is unique, then the onus is on you to show why technological intelligence is so strongly selected against.”
“We can’t extrapolate from our existence on Earth”, counters Andersen, “because it’s only one data point. We could be the only intelligent beings in the universe”, he writes, “or we could be one among trillions, and either way Earth’s natural history would look the exact same. Even if we could draw some crude inferences, the takeaways might not be so reassuring. It took two billion years for simple, single-celled life to spawn our primordial lineage, the eukaryotes.”
“And so far as we can tell”, he continued, “it only happened once. It took another billion years for eukaryotes to bootstrap into complex animal life, and hundreds of millions of years more for the development of language and sophisticated tool-making. And unlike the eye, or bodies with legs—adaptations that have arisen independently on many branches of life’s tree—intelligence of the spaceship-making sort has only emerged once, in all of Earth’s history. It just doesn’t seem like one of evolution’s go-to solutions.”
In 2012, Princeton astrophysical sciences professor Edwin Turner and lead author David Spiegel, with the Institute for Advanced Studies, analyzed what is known about the likelihood of life on other planets in an effort to separate the facts from the mere expectation that life exists outside of Earth. The researchers used a Bayesian analysis — which weighs how much of a scientific conclusion stems from actual data and how much comes from the prior assumptions of the scientist — to determine the probability of extraterrestrial life once the influence of these presumptions is minimized.
Their study argued that the idea that life has or could arise in an Earth-like environment has only a small amount of supporting evidence, most of it extrapolated from what is known about abiogenesis, or the emergence of life, on early Earth. Instead, their analysis showed that the expectations of life cropping up on exoplanets — those found outside Earth’s solar system — are largely based on the assumption that it would or will happen under the same conditions that allowed life to flourish on this planet.
In fact, the researchers concluded, the current knowledge about life on other planets suggests that it’s very possible that Earth is a cosmic aberration where life took shape unusually fast. If so, then the chances of the average terrestrial planet hosting life would be low.
“Fossil evidence suggests that life began very early in Earth’s history and that has led people to determine that life might be quite common in the universe because it happened so quickly here, but the knowledge about life on Earth simply doesn’t reveal much about the actual probability of life on other planets,” Turner said.
Evolutionary Bottlenecks on the Road to Technologically Advanced Civilizations
There are many evolutionary bottlenecks between abiogenesis and the development of a technologically advanced civilization. And scientists simply do not know all the types and significance of these bottlenecks. For example, our Moon stabilizes the Earth’s tilt into a nearly constant 23.4 degrees. Without the Moon, Earth’s tilt would vary wildly, leading to epochs with hardly any seasons and long periods with extreme seasonal variations. Whether advanced lifeforms could arise from such chaotic temperature variations is unknown. Our Moon formed due to a chance impact of a Mars-sized object with Earth early in the formation of our Solar System. The fraction of Earth-like planets in the habitable zone that have a large, stabilizing moon is unknown, as is the full role of such a large moon in the evolution of life.
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