Review of ZERO TO BIRTH
Every detail you didn’t know you wanted to know about brain development in utero
The human brain, made up of 86 billion neurons, is the most complex object in the known universe. Its unrivaled capacities, complexity, and mystery are slowly being uncovered as our technologies and knowledge advances – things that our very brain allows.
How does it get this way? How does it develop?
As it turns out, the nine months of we spend comfy and growing in our mother’s womb is the site of an astonishing amount of brain development. In fact, all the neurons we’ll ever have are produced before we’re born despite our brains being only 30% of adult size at birth. What happens in the brain from the moment of fertilization to a baby’s first breath on the outside? In Zero to Birth: How the Human Brain is Built, W. A. Harris shares every detail.
This book really is a masterpiece in terms of how much information is packed into this average sized book. Harris covers in utero brain development in a roughly chronological sequence, with each chapter highlighting a specific aspect of brain development.
Zero to Birth describes how neurons are made, then how they navigate to where they are supposed to be, and then how they know how to stop producing more neural stem cells and develop into functioning neurons. I found this last bit particularly interesting since it’s quite a feat of evolution to get our brains up to the size they are in terms of neuron number in a such a short time. Turns out, the cell division process neurons undergo is how.
Human neurons undergo several rounds of cell division, which allows for the astounding number of cells our brain contains. Neural stem cells in humans divide many times prior to “stopping” and developing into neurons, unlike other animals in which stem cells turn directly into neurons or divide only once more before doing so.
Once neurons are made, they need to get connected to other neurons, so they search for their friends. Connections are made between the transmitting axon of one neuron and the receiving dendrite of another. Once the connections — synapses — are made, neurons can now begin to communicate.
What is fascinating about this whole connection process is that our brains undergo periods of “refinement” – including a period in utero – whereby synaptic connections undergo a competitive process to see who remains. Connections that are better at communicating survive, those that don’t, die off.
What underlies much of these developmental processes is of course, chance. No single neuron has a specific plan of where it will end up and what it will be. Instead, the law of large numbers come into effect and – on average – things all work out. But the result of chance is inherent variation among human brains. These variations in connections and wiring give rise to what we call intelligence, personality, and asymmetries across our bodies.
Overall, this was a great book that I learned a lot from. That said, I also teach human development and intro psychology regularly, and have a PhD in psychology. The book is quite technical, and I think that if I were to read this with little psychology or neuroscience background, I would be a bit lost and might not get much from it.
Published: May 2022
Format: Hardcover
If you think this sounds interesting, bookmark these other great reads:
Innate: How the Wiring of our Brains Shape Who We Are by Kevin Mitchell (2018). Read my review.
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