In his paper purporting to show that a beneficial, baby-making “religion gene” will sweep through a population and eventually make everyone religious, Robert Rowthorn ignores this inconvenient fact: nearly everyone in the world is already religious. Here is how it breaks down:
Because fifty percent of the “Non-Religious” group is theistic but not “religious,” we can cut this number in half to 8%. And this number is surely lower given that the “Non-Religious” category includes those who express no religious preference but consider themselves to be “spiritual.” Though good statistics are lacking, it is probably safe to say that less than 2% of the world’s population is absolutely non-religious, non-spiritual, or non-metaphysical. No more than 1-2% of the world’s population, in other words, can be considered strict materialists.
What accounts for this fact? Has the “religion gene” already swept through the world’s population? Only 10,000 years ago, there were perhaps 5-10 million people worldwide. Today there are nearly 7 billion. Are we to suppose this exponential population explosion was caused by the spread of a high-fertility religion gene during the last 10,000 years? Surely not. The biggest change, and the primary driver of population growth, has been agriculture and industrialization.
There is, however, a sense in which all humans are predisposed to what Rowthorn blithely calls “religion.” We all have thousands and thousands of genes that code for a particular kind of neural apparatus. This apparatus has a focal point: the brain. Human brains have evolved in a manner which causes us to generate supernatural concepts. We do this naturally and it is a cross-cultural universal. What we today call “religion” rides on top of this biological substrate.
It is not, of course, very informative to say that humans have a whole mess of genes that create brains and these brains naturally generate supernatural concepts, which when culturally patterned are called “religions.” Humans do not have anything remotely approximating a religion gene or genes. We do have brain genes.
Rowthorn, R. (2011). Religion, fertility and genes: a dual inheritance model Proceedings of the Royal Society B: Biological Sciences