Scarcely a day passes without a report about genes associated with debilitating diseases such as early onset diabetes or breast cancer. Other genes allow you to happily eat ice cream and drink milk because Darwinian natural selection acted on your distant ancestors, allowing them to digest lactose beyond infancy. And you can hardly be unaware of the debate surrounding genetically modified organisms (GMOs) in the food chain or on the farm. Many of the genetic differences between humans and chimpanzees are now clear. Advances in genetic research are producing startling results. Trading on these developments, it isn’t surprising that a simple explanation for the way that we humans act has been accepted in academic circles and by most everyone else. We supposedly have genes that confer language, make us moral or religious, favor our close relatives, allow us to detect cheats, determine our taste in art, and so on. Simple solutions to complex problems are always appealing.
The focus here will be on research that points to understanding how the human brain evolved so as to allow us to choose between alternative courses of action and to create new possibilities—in short, the creative capacity that sets us aside from other species. Presently, no one can definitively tell you how the human brain works, but we can rule out the nineteenth-century models that guide the “gene that controls something” school of thought—whether it is language, math, morality, favoring relatives, and the like. Advances in neuroscience show that our brains do not operate in a manner similar to the components that make up digital computers. The biological brain doesn’t consist of independent “modules”—subsystems that each control a specific function, one module operating the keyboard or touch screen, another devoted to the display, and so on. Instead, specific structures of the brain clearly carry out particular “local” operations, but these operations don’t constitute an aspect of behavior that you can observe. The “instructions” for moving your arm forward, which involves a learning process carried out by a set of linked parts of the brain, are stored in the motor cortex, but even so seemingly simple a task as lifting a glass of water to your mouth involves pulling these instructions out of this motor memory store through local operations carried out in different parts of your brain, linked together in a “circuit.” I will describe some of these neural circuits and what they do, peeling away later in the text, the technical jargon.
Surprisingly, brain structures whose roots can be traced back to before the age of dinosaurs play a critical role in circuits involved in learning and executing motor acts, as well as in thinking. Neural circuits that first evolved for motor control were tweaked so that they regulate a range of linguistic and cognitive acts, including our creative ability to form new ways of acting and thinking, and choosing among them. Charles Darwin wasn’t aware of DNA, nor was he aware of the mechanisms of genetic evolution, but ongoing studies show that the guiding principles of evolution that Darwin proposed account for why we are not hairless chimpanzees, even though almost 99 percent of our genes are similar. Instead, natural selection acting on genetic variation, and the opportunistic use of existing organs adapted for one function to another, accounts for the neural bases of human language and our not being ruled by genes fixed in human prehistory or in our animal forbears.
The story isn’t over—we’re just at the starting point, but it is clear that determinist theories like those proposed by Noam Chomsky are untenable. As we’ll see, attested evidence of Darwinian natural selection acting on humans and the presence of genetic variation rule out Chomsky’s views, as well as related theories that claim that we have “moral genes,” “cheater-detector genes,” or “monogamy genes.” Other living species show signs of creativity, and that certainly was the case for extinct hominins such as the Neanderthals, but cultural innovation fueled by the enhanced creative capacities of human brains has made us the unpredictable species. The result is that we are able to shape our actions and destiny for better or worse.
Philip Lieberman
Providence, Rhode Island
May 30, 2012