We have been blinded by the excitement of discovering DNA. It has dominated biology, promising new worlds of eliminating diseases, customizing babies to parents’ orders, and “improving” every living thing. According to Alfonso Martinez Arias in The Master Builder, none of this is true, because we are looking in the wrong place.

DNA, he says, is a resource, a toolbox, not, as we are told repeatedly, an operating manual for all life. When questions arise like what eye color should be, how tall should the body be prepared to grow and what enzymes should the gut produce, DNA has the answers for all who care to read them. But when it comes to what to give birth to, what components the brain should have and where does the heart go, those decisions are made without reference to DNA, by the cells. Cells are the repository of all such knowledge, and are the only ones that can take action to make it happen. They are the master builders of the book’s title. DNA on its own can produce nothing. Cells drive everything and employ DNA as needed.

To prove the point, Arias focuses almost entirely on the embryo, where all kinds of action takes place immediately after the egg and sperm make contact. DNA is swept up by the process (copied and getting attached to chromosomes as they are built out), but is passive about it. Stem cells, particularly embryonic stem cells, are busy dividing, clustering and following their own roadmap of how to create a new human. They are on automatic drive, and will only consult the DNA at certain pre-programmed points.

Cellular life can go on without DNA, but DNA cannot go on without cellular life.

DNA, Arias says, is copied almost continuously throughout life, as cells of all kinds divide and die off. There is so much data stored in DNA that it is not possible to replicate it all perfectly every time. The result is numerous slightly different genomes scattered throughout the body, with genes that are broken, no longer make sense, or are damaging to the host body. Cells meanwhile, keep faithfully building the body throughout life. Skin is entirely replaced monthly, for example. And every new cell gets a copy of the DNA for itself, some 40 trillion of them in a human.

DNA’s passive role can be seen dramatically in twins, and Arias spends a lot of time on them. Suffice it to say that identical twins have different fingerprints. DNA was not asked for its opinion.
The fact that all DNA is structured the same way through all living things points to all living things descending from one living thing, and the happenstance creation of DNA being widespread enough that constant damage to it did not make it useless. So all the internet DNA-reading services that tell customers they were descended from ancient Egyptians or have Viking in their blood, are not saying anything outrageous. In less than half a million years, everyone’s DNA can still be traced back to the first human and the first living thing before it.

DNA is not itself a living thing, but it is “molecularly stable” and can be discovered after death. Cells however, need fuel, and die without it. This difference has led to all kinds of wild speculation, culminating in Jurassic Park, where dinosaurs could be raised anew because snippets of their DNA are still discoverable. Arias shows nothing of the kind is possible. DNA needs a cellular host, so unless we can come up with a female dinosaur to implant with the DNA, dinosaur DNA will not do the job of restoring them to life. Using a female elephant might produce something, but it will not be a dinosaur.

Yet another point of proof is the mouse, with which humans share 97% of identical DNA. This should be a screaming clue that DNA is not the driver of the process. Mice and men have far more differences than congruent traits, because it is their cells that determine them. DNA might determine hair color or baldness, tail length or color perception, but stem cells determine body style, leg numbers, symmetry of limbs, organs and sensors (mouths centered, one eye on each side of center, five fingers per hand, two nostrils centered, etc).

There is also an interesting chapter on perception. Humans find it necessary to pinpoint times and dates. The result has been a variety of definitions of life, when it begins, its stages, and so on. These were made in total ignorance for all of history. For example, we did not even know that women produced eggs just like any other female animal, until less than 200 years ago. The human egg, the diameter of a human hair, is all but invisible and has been hiding in plain sight since mankind came along. Without even knowing about eggs, the definitions of things like conception, embryos, viability and sustainable life are quite meaningless. Still today, Arias points out, we mislabel it all. It used to be that life was declared to begin when the mother first felt movement, between 18 and 20 weeks into the pregnancy. It was called the quickening. But even that was wrong.

Life does not begin at the quickening. Nor does it begin at conception, Arias says. A zygote cannot develop into a human outside the womb. The detectable heartbeat is not the defining point of viable life, as it is not pumping any blood to any organs, but merely operating – a dry run of sorts. The fetus cannot survive outside the womb until very late in the process. The percentage of fertilized eggs than reach live birth is stunningly low. Life only really begins with a successful birth.

The book is well illustrated with understandable drawings, proving what Arias claims from every angle. It is not a difficult read, which is a relief in biology books.

The problem with The Master Builder is in its main and only point: cells rule life. Arias makes this point again and again in differing stages, differing contexts, and differing processes. But it is the same point, over and over again. It can become tiresome for readers who aren’t totally fascinated by the physiological processes he describes. He writes credibly, with the facts plain for all to see. So by the end of the first chapters, readers will totally believe him. The rest is more of the same.

Just know that DNA is not the bottom line or the end of the story. Cells drive everything, including DNA.

David Wineberg

(The Master Builder, Alfonso Martinez Arias, August 2023)

If you liked this review, I invite you to read more in my book The Straight Dope. It’s an essay collection based on my first thousand reviews and what I learned. Right now it’s FREE for Prime members, otherwise — cheap! Reputed to be fascinating and a superfast read. And you already know it is well-written. https://www.amazon.com/Straight-Dope-learned-thousand-nonfiction-ebook/dp/B07Z48... ( )