Atheism and religion are not diametrically opposed to each other. In Chinese tradition, all the three major faiths -- Daoism, Buddhism and Confucianism -- are each both a religious belief and a non-religious metaphysical conviction at the same time, the former held by less educated folks while the latter by better educated scholars, generally speaking. This parallelism marked the more mature nature of the thousands of years long and still surviving Chinese civilization.                                                                                
                          -- The New Legalist editor

Atheists tend to be more intelligent than religious people because they are able to rise above the natural instinct to believe in a god or gods, scientists have said.

But according to Edward Dutton, from the Ulster Institute for Social Research in the U.K., and Dimitri Van der Linden, of the Rotterdam University in the Netherlands, this could also lead to their decline—in the same way high intelligence appears to have played a role in the fall of the Roman Empire.

Dutton and Van der Linder build on the theory that religion is instinctive, and it evolved as a behavior that helped humans become the highly successful species they are today.   

There has been a great deal of research into how religion originated, with the most prevalent idea being it evolved to help societies to form —believing there was heaven and hell, for example, would ensure cooperative, social behavior over fears of eternal damnation.

But now society has developed, why does religion still exist?

Ancient Greek and Roman texts show that even thousands of years ago, the link between intelligence, religion and atheism had been formed. More recently, scientific studies suggest a clear correlation between lower intelligence and religiousness.

In a study published in the journal Evolutionary Psychological Science, Dutton and Van der Linden say the link between higher intelligence and atheism, and lower intelligence with religion, can be accounted for by our instincts.

According to the study, our genes mean belief in religion is instinctive—it did, after all, help us develop as a species. Having a higher intelligence, they say, allows people to override these instincts and engage in more rational, and therefore enhanced problem-solving behavior.

But this is not all good news for non-believers, nor does it mean heightened intelligence will be selected, eventually leading to a species full of hyper-intelligent atheists. Instead, the ability to override your instincts would likely lead to a decline in intelligent, atheist people, because they are more likely to be antisocial and to have fewer children—or to not have them at all.

“It’s true that people who are less intelligent tend to have more children than people who are more intelligent,” Dutton tells Newsweek . “And intelligence is negatively associated with religiousness. So on that basis, you would expect religiousness to increase.

“If you have higher intelligence, you’re less instinctive. You’re lower in what you might call ‘evolved instincts’ that have evolved over thousands and thousands of years until the Industrial Revolution, when natural selection slowed down.”

He says that with intelligence being around 80 percent genetic, eventually there will be a decline in intelligence—and, as a result—a rise in religiousness. And this, he adds, could eventually lead to the fall of society. “It was commented on at the end of Rome, that the upper class weren’t having any children. It’s the same now,” he says.

Before the Industrial Revolution, parish records show that it used to be the richer, more intelligent people survived and had more children. As a result, society became more and more intelligent, up until the point of the widespread innovation of the Industrial Revolution.

“But these [breakthroughs] can only be sustained if we continue to have a certain level of intelligence, so if intelligence is decreasing then eventually the inventions that our ancestors were capable of coping with, we’ll no longer be able to cope with. We’ll go backwards,” Dutton says. “That’s what happened with the Romans.”

As a society becomes less religious, and more intelligent, we begin to lose the benefits religion brings in terms of group society. If a society becomes too intelligent, it becomes antisocial and stops breeding, and it eventually declines.

Next, Dutton plans to look more closely at the genetics of atheism, not only that it reflects high intelligence and low instincts, but that our instincts might be changing. If natural selection is becoming weaker, there may be a propensity towards instincts that would have been removed under natural selection. These instincts may have been disfavored because of their association with poor genetic health, he explains—and atheism could be an example of this.

“I think most people think it is rational to be an atheist,” he says. “But the reason why people are atheist is not necessarily some logical reasoned choice.”