Life Unfolding: How the Human Body Creates Itself

Citation

Davies, J. A. (2015). Life Unfolding: How the Human Body Creates Itself. Oxford University Press. (Original work published 2014.)

Chapter Summary

The book was first published in hardback in February 2014 and in paperback in 2015. It runs to about 300 pages: an opening chapter and eighteen further chapters in four parts, followed by references and an index. Its author is a developmental biologist at the University of Edinburgh. According to the publisher, the book tells the story of human development from egg to adult in terms of one central principle, "adaptive self-organization". This is the idea that interactions among many cells, and among the molecular machines inside them, can organise tissues far larger than themselves, correcting errors as they go and adding new layers of complexity. Davies describes the book as an attempt to explain this clearly and accessibly, with an emphasis on a systems approach: how feedback lets small units that carry very little information build structures at a much larger scale. Many chapter titles are allusive, so the outline below keeps to what the titles, the part headings and the publisher's description show.

Chapter 1: Confronting an alien technology

The opening chapter stands outside the four parts. Its title presents the body's way of building itself as something fundamentally unlike human engineering. The Publishers Weekly review summarises the theme: bodies build themselves very differently from the way we build houses, with no boss in charge and control located everywhere.

Part I, First Sketch — Chapters 2–6: From one cell to many; Making a difference; Laying down a body plan; Beginning a brain; Long division

The first part covers the earliest stages: going from the fertilised egg to many cells, making those cells differ from one another, establishing the basic body plan and beginning the brain. "Long division" closes the part; its subject is not stated in the sources and it is best read in the book itself.

Part II, Adding Details — Chapters 7–13: Fateful conversations; Inner journeys; Plumbing; Organizing organs; Taking up arms (and legs); The Y and how; Wired

The second part fills in the sketch. The chapter titles point to signalling between cells, cell movements within the embryo, the vessels and tubes of the body, the formation of organs, the growth of arms and legs, the role of the Y chromosome and the wiring of the nervous system. The Publishers Weekly review describes the strategies at work as interactions between secreted proteins, cell surfaces with different receptors and adhesion properties, and eventually molecular messages from different parts of the brain.

Part III, Refinement — Chapters 14–18: Dying to be human; Making your mind up; A sense of proportion; Making friends and facing enemies; Maintenance mode

The third part deals with processes that refine the body after its basic construction. The titles suggest cell death as part of normal development, the shaping of the mind (the reviewer notes activity-dependent wiring and rewiring of neurons), the control of body proportions, the immune system's distinction between friend and foe, and the maintenance of the body in adult life. The publisher states that the book highlights how embryological knowledge is used to understand why bodies age and fail.

Part IV, Perspectives — Chapter 19: Perspectives

The final part has one chapter. According to the Publishers Weekly review, Davies argues here that the future lies in studying larger patterns of gene expression and of cell connections, networks that may reveal universal principles.

Key Concepts

Chapter 1 and Part I: Confronting an alien technology; First sketch

• Self-organisation: the building of large, complex structures from local interactions among cells, without a central plan or controller.
• Adaptive self-organisation: self-organisation that corrects its own errors as it proceeds, the book's central principle.
• Body plan: the basic layout of the body established early in development.

Part II: Adding details

• Cell signalling: communication between cells by secreted proteins and surface receptors, which decides what cells become.
• Cell adhesion: differences in how cells stick together, used to sort and shape tissues.
• Organ formation: the construction of organs, limbs, vessels and nerve connections from the early embryo.

Parts III–IV: Refinement; Perspectives

• Activity-dependent wiring: the refinement of neural connections by their own activity.
• Feedback: the mechanism by which small, simple units can organise and regulate structures far larger than themselves.
• Maintenance and ageing: the body's continuing work to stay organised in adult life, and what happens when it fails.

Critical Analysis

Strengths

• A single unifying idea. Adaptive self-organisation runs through the whole book, according to both the publisher and the author's own description. This gives a non-specialist a way of understanding development as a set of related processes rather than a catalogue of facts. The author's stated emphasis on feedback and control brings ideas from systems biology into the story.
• Human-centred. The book follows the human body from egg to adult and on into maintenance and ageing. Readers interested in their own bodies or in medicine will find the subject directly relevant.
• Coverage beyond the embryo. The third part carries the story into the shaping of the mind, body proportions, immunity and maintenance, linking development to physiology, ageing and disease.
• Reviewed as useful for students. Publishers Weekly judged that students of developmental biology will find the work useful. Scientific American's notice describes it as setting out what is and is not known about how small components produce the complexity of life.

Limitations

• Dense for general readers. The Publishers Weekly reviewer, while recommending it to students, found it rather dense for a general readership. Readers without school biology should expect some hard going.
• Not a textbook. The book is a narrative about the human body for general readers and students. It is not organised for systematic study of model organisms and experiments, and it does not replace a course text.
• A 2014 snapshot. The state of research is that of the early 2010s. Developments since then, for example in organoids and single-cell methods, are outside its scope.

Where It Fits in the Course

Among the developmental biology books on this list, Life Unfolding is the longer of the two books for general readers. Lewis Wolpert's Developmental Biology: A Very Short Introduction covers the basic processes of development across vertebrates, invertebrates and plants in about 130 pages. It is the quicker first read and gives the comparative background that Davies, who concentrates on humans, does not aim to provide. Reading Wolpert first and Davies second works well: Wolpert supplies the vocabulary, and Davies adds the systems view and the human story.

For a course, Slack and Dale's Essential Developmental Biology and Barresi and Gilbert's Developmental Biology are the textbooks that cover model organisms, experiments and mechanisms systematically. Wolpert's Principles of Development is an advanced textbook for readers with a background in cell and molecular biology. Carroll, Grenier and Weatherbee's From DNA to Diversity treats the evolution of animal form, a theme Davies touches only indirectly. Davies's book is best read alongside one of these textbooks, as a narrative that ties the mechanisms together.

How to Use This Book

The book is written for general readers and students. School biology is the background assumed, but readers will benefit from some familiarity with cells and genes, given the density the reviewer noted.

• Read in order: the book is a narrative from egg to adult, and the four parts build on each other. Chapter 1 sets out the central idea and should not be skipped.
• Core for students: Parts I and II, which cover the early embryo and the building of organs and tissues, the material of most developmental biology courses.
• For wider interests: Part III on the nervous system, immunity, body proportions and maintenance suits students of neuroscience, immunology or medicine. The final chapter is useful for anyone thinking about research directions.
• Alongside a course: after each textbook unit, read the matching Davies chapter and ask how feedback and self-organisation explain the mechanisms just studied.