No Space Aliens? Are We Alone in the Universe?

Why Are There No Visitors From Outer Space?

Part II – Primates and culture

Originally, scientists thought that intelligent life should be somewhat common in the universe. All one had to do was to estimate the number of planets in the habitable zones of their stars in our galaxy, and there were an unlimited number of candidates. The prebiotic molecules that help kick-start life can be found throughout the universe. So life made up of single cells is probably common on many planets.

Part I of this series covered the roadblocks to intelligent life based on planet and sun type, and simple cell biology. There we learned that the development of eukaryotes was unlikely on most planets capable of life, and no intelligent life would emerge. Assuming, however, that eukaryotes do appear, in this segment we discuss what further roadblocks to intelligent life exist after complex multicellular lifeforms evolve.

Roadblock 2 – Lack of Primates

Animals that have reached a human level of intelligence, and able to physically manipulate their environment, have only been certain primates. Living in trees, they first used their legs to walk upright on tree branches while holding on to higher tree branches with their arms, then walked on the ground with their arms free to carry provisions. No other animal form on Earth has reached human intelligence capabilities.

It was very unlikely that the asteroid that struck the Earth and led to the dinosaur's demise would land where it did. Half of the Earth's surface is deep water where an asteroid strike would not have much significance. So the evolution of primates on Earth was a fluke caused by an asteroid landing in the worst possible place to cause mass extinction of large animals.

The primate genus homo, which appeared 2.8 million years ago, happened 4.3 billion years after the Earth first formed. It took a long time to get that far, and there was no guarantee it would happen. What we have to conclude is that another roadblock to the development of a technologically intelligent species is the absence of primate-like animals.

Roadblock 3 – Lack of permanent towns and farming

Most of human history is that of bands of roaming foragers living off the land. Only when human populations grew too dense to sustain themselves foraging food in the wild did farming and a more settled way of life in villages appear. However, Neanderthals and Denisovans never produced growing populations that required settlements and farming. If a species like modern humans with its rapid population growth does not appear, civilization, with the motivation to develop a writing system and recorded information, may never develop.

Roadblock 4 – Religion

The first modern human philosophy explaining how the world came about was religion. Religion is not only widespread in all human cultures, it is easy to understand by the simplest of men. It tends to lead away from a rational, logical approach to the world to one that is more subjective. It is also very effective in combating other philosophies, such as science, and will often drive them out of society, by banishment of, or killing, its advocates.

Roadblock 5 – Lack of science

Science is the methodical study of the observable universe for the purpose of understanding the laws by which the universe is governed. This philosophy was invented by the Greek philosopher Aristotle. He was the only one in the world to develop this idea and pass it along to others. Without Aristotle, would science have been invented and accepted by society anywhere?

Roadblock 6 – Wars, religious opposition

Science had to go through a gauntlet of challenges before gaining widespread acceptance. It developed slowly in the Roman empire, but the Islamic conquest took over the southern Mediterranean and with it, much of the literature of the Roman world. Some forward-thinking sultans paid for the development of scholarly knowledge after the conquest. The Islamic world developed scientific methodology, optics, and algebra. Then money dried up because of wars with invading barbarians, and Islamic leaders declared that religion had been perfected and no further development of knowledge was needed.

An entire library of Islamic literature in Toledo, Spain, was gifted to the Spanish who translated it to Latin. Science began further development in the Christian world until it was effectively banned by the Catholic church. Ironically, it was banned because Galileo's teachings disagreed with those of Aristotle, whom the Church had adopted as the ultimate scientific authority, even though frequently wrong and out of date.

Some scientists fled to Protestant countries where the Pope had little influence. There, they continued to develop science, picking up the Protestant religious idea that one should do honest work to be worthy. Science flourished in Protestant countries, giving us physics, chemistry, biology, and eventually, electric power, radio communications, and solid-state electronics.

Science could have been abandoned if Islam had treated Roman literature as unreligious and unworthy. It could have been shut down if the Christian world had not obtained the scientific knowledge of the Islamic world. If the Protestant Reformation was not underway, there would have been no safe haven for scientists after the Catholic church crackdown.

Conclusions

There could be intelligent communities on other planets, just without the technology to communicate with us or to visit. On the whole, we must agree with one scientific assessment that the number of intelligent civilizations in the universe with advanced technology is a maximum of two civilizations per galaxy to as few as one per four galaxies.

In other words, we have not been visited by aliens from outer space and we will likely never encounter any. At present, we do not have the ability to travel, in a space ship, as much as one-quarter of the way through our own milky way galaxy, except using robots. The distances and travel time are prohibitive for even one galaxy.