Image of brain

In the messiness of determining why and how people are who they are, Innate: How the Wiring of Our Brains Shapes Who We Are, by Kevin J. Mitchell, feels like a lucid, up-to-the-minute account of the human mind. Mitchell, a neuroscientist, blogger, and associate professor at Trinity College Dublin, explores the diversity of our brains, explaining how we become different individuals despite using the same genetic blueprint.

Beginning from the foundations of our DNA, Mitchell blends our sometimes-black-and-white understanding of nature vs. nurture, building a framework for the reader to understand how our biological code manifests itself to shape anything from genetic influences on schizophrenia and epilepsy, to abstract traits of personality and intelligence. In considering the social, ethical, and philosophical implications of the accumulation of scientific discoveries, Mitchell changes the paradigm of what truly defines human nature.

Below is an excerpt from Innate, published this month by Princeton University Press.

Cover of Innate

The Essence of Intelligence

At its core, intelligence is the ability to think in more and more abstract ways—to see a specific instance of something and draw larger lessons from it, which can then be applied to other situations, by analogy. We can go from learning that “A causes B” to extrapolating that “things like A can cause things like B.” That power of analogy is at the very heart of our intelligence—it is, in fact, explicitly included in questions on IQ tests, like: “Acorn is to tree as puppy is to __.” The analogy in that example is based on a quite concrete relationship, but, with increasing brainpower, analogies can be made across higher-order properties of categories of things or events or situations.

Let me make an analogy. The hierarchical organization of our visual system allows us to extract features of the visual scene of higher and higher order. Each area integrates information from the lower areas and extracts a more complex model of the world—first just dots and flashes, then lines and edges, then shapes and objects, then types of objects—tools, animals, faces—until we get to a stage where we can categorize objects as the same thing—say, a chair—despite seeing it from different angles, and we can recognize multiple different things as being members of the same category, based on their higher-order properties (like having multiple legs and a flat bit to sit on, for example). Our cognitive systems do the same thing. As the cerebral cortex got larger, it led to the emergence of new areas, so that the hierarchy had more levels, each one able to integrate more sophisticated information from lower levels and discern more and more abstract properties.

When we talk about intelligent behavior we mean the deployment of such abilities to recognize the relevant dynamics of novel situations, to anticipate events, to imagine the consequences or outcomes of a range of possible actions. Intelligent beings are not just driven by hardwired instincts or even by learned responses to specific stimuli—they can use the abstract principles gleaned from prior experience to adapt to new situations and environments.

At some point in evolution, the increasing ability to think in abstract terms—to have ideas—led to, and was reinforced by, the emergence of language. How this happened is a mystery, of course, tied up with the emergence of consciousness itself, which is definitely a topic for another day. But the consequences were profound. Now the advantages of each individual’s big brain were massively amplified by the ability to communicate ideas with each other. Now if I learned something useful, I could tell you; if I had a good idea, I could pass it on so everyone in the group benefited. Then children didn’t have to relearn everything anew from their own experiences—instead, they could build on the previous hard-won knowledge of their parents, and of others in the group.

Culture was born. And cultural evolution started to interact and collaborate with biological evolution. Where, previously, being more intelligent gave some advantage, now it gave a huge advantage. And the more intelligent we got, the better it became to be even more intelligent. This snowball effect meant that we started to be able to transcend the normal rules of natural selection. We made our own niche—the cognitive niche. Instead of being selected by our environments at the glacially slow pace of evolution, we had the flexibility to adapt to them on the fly, and eventually to flip the process entirely—now we were in the driver’s seat, adapting our environments to our own ends. In the process we changed the selective pressures acting on new mutations, greatly favoring any that further increased intelligence. The only thing that put the brakes on this process of positive feedback is thought to have been a size constraint—our heads became too big for the birth canal. Or perhaps the metabolic costs of our big brains, which use about 20% of our energy, just became too high. However it happened, we ended up with intellects leagues beyond our nearest relatives.

See also: Neuroscientists Uncover the Roots of the Uniquely Large Human Brain

Because of its central role in our evolution, when it comes to variation in intelligence across people today, this seems, more than other traits, to carry a kind of value judgment with it. Unlike many personality traits, where variation is seen as fairly neutral—where it’s not obviously, or at least not consistently, better to be, say, more extraverted, or less neurotic—variation in intelligence is not neutral. All other things being equal, higher intelligence is better than lower intelligence.

We’ll see how this idea influenced the dark policies of eugenics that were widespread across many countries in the twentieth century (and that are, in some places, experiencing a surprising resurgence, though perhaps in a more benign form). Supporters of eugenic policies made the unwarranted extrapolation that a more intelligent person is better than a less intelligent person. The idea of judging the “quality” or “worth” of a person at all is repugnant (to me at least, though apparently not to everyone), but if one were to engage in such a practice, intelligence is just one of many personality and character traits that we might throw into the mix (honesty, integrity, kindness, courage, and selflessness all spring to mind as equally valuable elements of our humanity). In any case, given the history and attitude of eugenics, it is not surprising that there was and continues to be a strong backlash against the very idea that intelligence is in any way innate.

In what follows, I will try to separate the science from these kinds of extrapolations, though we will return in chapter 11 to the societal implications of the scientific findings and especially to the subject of eugenics. For now, what follows from the discussion of the evolution of the intelligence of humans as a species should be obvious: that difference, between us and other animals, is genetic. Cultural evolution played a central enabling role, but, ultimately, we each have human intellectual capacities because the program for a complex human brain is written into our DNA. It should not be a surprise, then, that variation in that genetic program could exist between people and could contribute to variation in their intelligence. Indeed, it would be a surprise if it didn’t.

Excerpted from Innate: How the Wiring of Our Brains Shapes Who We Are* by Kevin J. Mitchell. Copyright © 2018. Published by Princeton University Press

Innate: How the Wiring of Our Brains Shapes Who We Are is published on October 16, available now.

Photos via Princeton University Press, Pixabay