Evolution and the mind: science and speculation

The Birth of the Mind, by Gary Marcus, tells a fascinating story discovered in recent years about how genes drive the development of the brain. The primary puzzle is how 30,000 genes enable the creation of billions of neurons and trillions of connections. The answer is that genes aren’t like a blueprint with each gene coding for a component. Instead, genes act like computer programs, with behavior that is switched on and modified based on developmental and contextual cues. Brain wiring isn’t complete at birth or in childhood. Learning consists of rewiring the brain across the human lifespan.

Marcus hypothesizes for further research that the difference betweeen humans and chimpanzees isn’t just brain size, it’s differences in the developmental program. The same components are re-used and extended — the “then” parts of the genetic conditionals — the proteins produced — are the same but the “if” sections are different — the conditions and sequence in which the proteins are produced.

One of the interesting areas of discovery how modules are repurposed. The FOXP2 gene has been discovered to play a role in human language capabilities; it’s also used in the heart, lungs, and other areas. Another gene, PAX6, which controls eye-building, also used for “development of the central nervous system and endocrine glands, and regulates a range of cellular processes, including proliferation, migration, adhesion and signalling.” (from this paper by Marcus on FOXP2).

The story Marcus tells is complementary to the science sections of The Symbolic Species: The Coevolution of Language and the Brain, which describes the developmental patterns of neural growth. In human brains, neurons get extend and infiltrate from motory, sensory, and emotional centers through to centers of reason and planning, extending vocal calls to speech, foraging instincts to ethnic cuisine, emotions to poetry, weddings and funerals.

Unlike the Symbolic Species and recent books by Steven Pinker, Gary Marcus’ mentor at MIT, this book doesn’t stray as far into unprovable speculation about human nature and the origins of consciousness and culture. Which is just as well — the science is fascinating with less speculation. It is quite a thrill to read about a body of scientific knowledge that is growing so rapidly.

Daniel Dennett’s Freedom Evolves is on the speculation side of the continuum. No surprise, since Dennett’s a philosopher. The book tries to show how evolution can give rise to free will.
The first part of the book is a defense of an old philosophical perspective called “compatibilism”, whereby human free will is compatible with a deterministic universe. Even though natural events are predetermined, humans can choose to avoid determined events. For example, I might be genetically nearsighted, but can choose to wear glasses. The logical failure case is the intersection of multiple agents that each have free will. Ghandi chose nonviolent tactics to oppose British colonial rule, Indians chose to follow Gandhi’s nonviolent approach, and the British agreed to concede.

Following the defense of compatibilism, Dennett cites game theory and evolutionary biology to explain how humans may have evolved tendencies to co-operate, to develop ethical norms and social judgement. Dennett’s discussion of ethics seems rather impoverished. The examples he gives are mostly about the use of prison as just punishment, rather than the less extreme ethical issues that pervade social life. When discussing “free will”, Dennett tries to zero in on the rare circumstance of pure free choice, rather than the common situations where ones choices are influenced by habits (which one has chosen at some earlier date).

Dennett is vehemently in opposition to traditional, religiously derived perspectives. The book is studded with barbs against unnamed opponents who are supposedly terrified of the liberating impact of Dennett’s evolutionarily derived secular philosophy.

Yet spiritual thinkers from various traditions have more nuanced and insightful discussions about the range of ethical behavior, from parent-child relationships, to social gossip, to business ethics, to more extreme cases of crime and punishment. It is commonplace in Jewish ethical writing, for example, to talk about choosing good companions, teachers and habits to foster good choices.

Like Steven Pinker, Dennett scornfully replaces traditional ethical thought with modern, science-justified speculations that don’t, however, seem particularly wise. It is possible that moral philosophy guided by evolutionary science will contribute wisdom about the human condition; but these writers haven’t done it.
The developing science of mind, shaped by research in genetics, developmental biology, psychology, computational modeling, and evolutionary analysis is generating fascinating results. So far, the science seems more compelling to me than the philosophical speculation surrounding it.

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