Ancestral testing is “astrology.” We need to relearn everything we know about DNA and cells

Genes are necessary for the development and maintenance of tissues, but from the layout of the body to the organization and functioning of our nervous system, cells control their expression and make us who and what we are.

Throughout the 20th century and continuing to the present day, the common belief has been that our personality is tightly linked to our DNA. While there is some truth here – as Shakespeare said, “What is past is history” – when it comes to development, cells and genes have a very different relationship with history. It is therefore appropriate to pause for a moment to briefly revisit the reasons behind the dominant view of the genome as the master of our lives.

This idea lies in the content of DNA, those strings of Gs, Cs, As, and Ts that make up the hardware store catalog that is your genome. This catalog has been updated over millions of years and is unique to each of us, not in its repertoire of tools and equipment but in colors and design details. Through these subtle differences, in the same way you can trace the evolution of 1950s computers on your iPhone, you can trace the history in your genome, a history based on the correlation of differences and similarities of the script. . Add a historical explanation to these genetic relationships – genealogies – and you will have ancestors, generations that, so you are told, connect distant peoples and places and, if you go back far enough, connect all people to each other.

We humans feel a great need to be friends, to know our origins, and because we have been genetically engineered for the past hundred years, we have been using genetic language to write our stories. The big hitters in commercial DNA testing, Ancestry.com and 23andMe, together store the genomes of more than 30 million people in their books. Based on this data, you can tell that you are 37% Western, 27% German, 26% Scottish, and 10% Nigerian, give or take 10 to 20%, or that 2% of your DNA is Neanderthal (as it is, on average, for all people alive today, because of how humans evolved). Some companies claim to be able to match your DNA with that of, say, Vikings, ancient Egyptians, Chumash Indians, and other people who lived a few thousand years ago. Being a pharaoh’s descendant!

There is great appeal in the thought of communicating with distant people, places and times. But as the organization Sense About Science says of such claims, “It’s not just genetics.” Geneticist Adam Rutherford rightly pointed out that if you go back far enough – and “far enough” is not all that far back in human history – we are all related. This is the truth. The tools and editing in the genome is what we need to become an animal, a primate, a human, so it’s not too surprising that there is a lot of overlap.

Genetic ancestry can be measured, say we are 50% this or 25% that, but what do these numbers really mean? Do these numbers say anything about who we are today? The history of our species may be carried in our genome, but our genome does not make us who and what we are.

An equally fascinating view of human history is contained in the story of how our cells create us, division by division, beginning with the first division of the zygote and building up divisions along the way. Remember the point of embryonic development noticed by Karl Ernst von Baer: that, right after eating, the process that sets the plan of the organism, we look very similar to chicken, fish and frog. The similarity of animal embryos connects us to many primitive organisms. Eukaryotic cells – those with a “true,” or well-formed, nucleus – began to use the genome in new ways, controlling genes so that they could combine to build a strong, functional organism that could conquer the planet.

To achieve this, the cells have found a few efficient methods, such as the bilaterian body plan (left and right sides) and gastrulation. In all animals, cells draw upon the same set of tools and materials to form the basis of the body. Then, after gastrulation, they go their separate ways, building special characteristics of species and special things, individuals, based on their interaction with each other, because we are mammals, our central connection is with our mother. The building process does not end at birth; it continues throughout our lives, as our stem cells produce new cells to keep our bodies functioning properly.

Our genes are not our identity, no matter what the DNA testing companies say in their marketing campaigns. In fact, these companies use DNA from human experiments to research how to treat diseases caused by single gene mutations. In other words, they know that genes are tools, and they are looking for ways to use the fact that these tools can be modified at times.