Review: Kevin J. Mitchell’s “Innate”

by Miles Raymer


People who study the classic scientific debate between nature and nurture tend to reach some version of this conclusion: It’s complicated, both sides make significant contributions to human behavior, and we should never be too quick to attribute a particular outcome solely to genetic or environmental factors. Kevin J. Mitchell’s Innate doesn’t completely overturn this paradigm, but it definitely modifies it in ways that feel fresh and exciting.

Innate is a dense but accessible analysis of cutting-edge findings from genetics, neuroscience and psychology. Mitchell has a true talent for condensing complex scientific concepts into graspable prose, and includes many well-designed visuals to complement his research. His thesis posits not only that the existence of innate personality traits is inarguable, but also that these traits appear to have a larger impact on our selection of behaviors and experiences than previously thought. He explains:

The debate about the relative contributions of nature and nurture to our psychological makeup is classically framed as a battle between these two forces, rather than, say, a collaboration. In recent times, this has turned into a proxy war, with genetics on one side and brain plasticity on the other, lately allied with the shadowy forces of “epigenetics.” If the brain can change itself, and if we can turn our genes on or off by our own behavior (which is what some proponents of epigenetics rather nebulously claim), then it seems we could reverse the arrows of causation––our psychology could dictate our biology, rather than the other way around.

Under this scheme, nurture––whether this refers to parenting, experiences, or our own conscious psychological practices––can trump nature. It can overwrite the innate differences in our brains that arise due to genetic and developmental variation. In fact, what tends to happen is just the opposite––initial differences tend to be amplified due to the self-organizing processes of brain development and the fact that individuals select and construct their own environments and experiences largely based on innate predispositions. This is a radically different conception, where the processes of brain plasticity––the supposed instruments of nurture––align with nature instead. (81)

I found the first component of Mitchell’s argument––that innate predispositions exist and obtain from an individual’s genetic makeup––to be neither controversial nor unfamiliar. The second component, however, was much more novel. Mitchell zooms in on the highly probabilistic and unpredictable nature of brain development, whereby each human body physically constructs its brain according to a person’s unique genome:

The complex machinery of the brain emerges from instructions encoded in the genome, but it is not mapped out like a blueprint––there is no one part of the genome that corresponds to one part of the brain or one type of nerve cell. It is more like a recipe, or a series of protocols, which, when carried out faithfully, result in a human being with a human brain. And, just like a recipe, no matter how detailed and precise it is, there will inevitably be some differences in the outcome from run to run––you can’t bake the same cake twice. (54)

This process, which Mitchell helpfully refers to as “prewiring” (as opposed to “hardwiring,” which implies genetic determinism), exerts a massive impact on a person’s way of seeing and interacting with the world. The descriptions of prewiring in Innate are quite intricate for a popular science book, but Mitchell does a commendable job of leading the reader through the major self-organizing layers of brain development, revealing a vast and impressive array of pathways through which each person’s genetic program builds a brand new and completely unique brain. Mitchell gathers these factors under an umbrella concept called “robustness,” with each person thrown into a genetic lottery that can increase or decrease chances of efficacious development:

There is an unexpected consequence of the way developmental systems are designed, which is a paradoxical fragility to certain kinds of perturbations, especially mutations in developmental genes. The robustness that evolved to buffer noise and environmental variables means the system can also absorb the effects of many mutations affecting the components of the developmental programs. But not all of them…We all carry thousands of minor genetic variants and typically 100-200 major mutations. So none of us has a developmental program that is as robust as it could be. If you or I were cloned 100 times, the result would be 100 new individuals, each one of a kind. (77-8)

Importantly, although the development of each individual brain is subject to a wide range of variability (each recipe can bake many potential cakes), which brain ultimately gets “baked” appears to be either minimally affected or completely unaffected by factors outside the body––the traditional forces of nurture. This means that the “world outside” the body has little to no impact on the development of our innate predispositions, at least when a person undergoes normal, healthy development (the effects of adverse childhood experiences may represent a categorical exception). Furthermore, as stated above, it is Mitchell’s view that these same predispositions tend to be reinforced and compounded by our environments and experiences, rather than challenged or subverted by them. Whether this assertion will stand the tests of time and scientific scrutiny remains to be seen, but as a first stab Mitchell’s case is compelling and well-supported.

Assuming Mitchell’s thesis is correct, what are the implications of shifting the nature/nurture debate in this direction? First, it is critical to point out that Mitchell is not a genetic determinist who believes that nature is the only game in town:

The claim is far more modest. It is simply this: that variation in our genes and the way our brains develop causes differences in innate behavioral predispositions––variation in our behavioral tendencies and capacities. Those predispositions certainly influence how we behave in any given circumstance but do not by themselves determine it––they just generate a baseline on top of which other processes act. We learn from experiences, we adapt to our environments, we develop habitual ways of acting that are in part driven by our personality traits, but that are also appropriately context dependent. (264, emphasis his)

So, we shouldn’t interpret these findings as nullifications of the traditional forces of nurture, but we also shouldn’t downplay the powerful role of nature. By and large, innate differences between people are not the products of conscious human choices; they are not particularly sensitive to our intellectual discoveries, cultural traditions, or ethical convictions, and instead are received from the statistical crapshoot of developmental robustness and the contingent whims of our biological history. The fact that we are a sexually dimorphic species is the starkest example of this, and Mitchell includes an entire chapter addressing the significant and undeniable differences between men and women. He also explores the nature of variations in human perception, intelligence and mental illness, putting forth his own spin on how innateness operates in each field of study.

I think Innate is a good and worthwhile book, but I would like to point out one area where Mitchell’s intellectual consistency seems to falter. In his last chapter, he claims that his point of view does not align with determinism––that his research shouldn’t lead readers to conclude that people don’t have free will. I think Mitchell does a fine job of avoiding genetic determinism and neuroscientific reductionism, but I think he fails to refute determinism in the more general sense. In fact, Innate contains some of the strongest arguments I’ve encountered that support the determinist position and undermine the commonplace concept of free will.

Mitchell tries to split the difference by acknowledging that our freedom is constrained by biology and that “free will doesn’t mean doing things for no reason, it means doing them for your reasons” (266, emphasis his). However, the entire rest of his book could be interpreted as an extremely detailed and convincing explanation of exactly how little “choice” people get in shaping their motivations and reasons for action. It seems unclear, then, how we are supposed to feel the kind of personal ownership over our motivations and actions that would confer a legitimate sense of self-determined freedom. It would be better to admit that there’s no scientific evidence to support free will, and to point out that this reality doesn’t require us to completely surrender our notions of personal and social accountability. Rather, we ought to utilize the nonexistence of free will as a bedrock motivation for a compassion-based overhaul of our institutional responses to aberrant and violent behaviors. Mitchell’s failure to make this move constitutes a lost opportunity.

I don’t need to agree with Mitchell about everything in order to appreciate his valuable contribution to these fascinating and consequential subjects. The best of these is perhaps the intellectual tools Mitchell provides for “reality-proofing” our expectations of ourselves and others. Since people arrive on Earth with well-developed and wide-ranging predispositional palettes, we must accept that human communities are a mosaic of profoundly variable perceptions, preferences and reactions to our ever-changing world. There is a strong limit to how moldable people can become, and we must adapt our models of growth and learning to promote achievable progress while also rejecting the project of human perfectibility:

There is a power in accepting people the way they are––our friends, partners, workmates, children, siblings, and especially ourselves. People really are born different from each other and those differences persist…Denying those differences or constantly telling people they should change is not helpful to anyone. We should recognize the diversity of our human natures, accept it, embrace it, and even celebrate it. (269)

Rating: 8/10