All the heritage that hides under people’s skin

Diversity is not what we thought. It is much less obvious than it seems, as it is not always recognized by the naked eye. That’s what the publicist makes clear Carl Zimmer in the book He has his mother’s smile (Swing Captain), Published in Spanish in the first half of 2023, and which was elected ‘Science Book of the Year’ in 2018 by The Guardian newspaper.

It is about knowing the apparent similarities and differences that are hidden under people’s skin, at a time when Diversity It has become a term of controversy. For some, diversity constitutes a virtue and wealth for societies; for others, a problem, when they fear that their own traditions, customs or physical traits will be diluted.

Zimmer explains in his essay that if we found genetic similarities with people from other continents, we would hardly be able to guess just by naming or looking at each other. The genetic variants underlying our traits are invisible to the naked eye, tens of thousands of years after the first human migrations.

In fact, between 50,000 and 80,000 years ago, a group of humans expanded out of africa and, according to the author, today these genetic variants are found in Australia and India, among other regions. Meanwhile, a genetic mutation drastically reduced a skin pigment and the hunter-gatherers they continued to open routes to the north and west.

The author begins his book by narrating a visit to the obstetrician, before the birth of his first daughter, who recommends consulting a genetic counselor.

He has a smile… translation by Patricia Teixidor, contains almost 700 pages of an amusing story about it that is already on everyone’s lips. Because genetic studies are currently being talked about in almost all areas of science, from biomedicine, to discover causes and possible therapeutic targets from rare pathologies to paleontology, when bones are unearthed and dated fossils of dinosaurs.

But genetics also occupies a few pages of gossip, when celebrities go to an egg or sperm donor bank to have children (or grandchildren). In addition, recently, we heard the news of the pardon of a woman —accused of killing her four children— when she discovered that they had all suffered the same hereditary disease fatal. At the other extreme, genetic studies led to the trial of a man suspected of fathering more than 550 children for his compulsion to donate sperm.

Questions for new parents

Carl Zimmer is one of those popularizers who usually starts his work with an anecdote that attracts us. Here she does it with a visit to the obstetrician, before the birth of her first daughter, who recommends consulting a genetic counselor.

What can frighten parents expecting their first child more than the ghosts that grow up in the face of the unknown?

Since hominid skin does not fossilize, we cannot say with certainty what the skin color of our ancestors was four million years ago.

Down syndrome wasn’t the only thing prospective parents should have wondered about, notes the author. “It was possible that we both carried genetic variations that we could pass on to our daughter, causing other diseases,” he argues.

The author remembers that the geneticist took a piece of paper and drew a Genealogy to show them how genes are inherited. The 21st century was beginning and it had just been announced that the first study of the entire human genome had been completed.

Two decades later, what do we expect from genes we inherit? This is a question that assails us, among the first curiosities of this time when amazing stories are known, half regulations, disparate from country to country, and “racial” arguments to vetoes and sociological theories not always well intentioned.

Has Europe always been white?

“Ancient DNA showed that white people do not share a genetic link deep and pure dating back to the earliest days of human occupation of Europe,” observes Zimmer. “The first homo sapiens who arrived in Europe are not directly related to current Europeans”, in his words.

In fact, “the European people can trace their ancestry back to the peoples who arrived on the continent in a series of waves separated by thousands of years”, he assures, as if to make it clear that there are kinships that we do not know and strangers to whom we are linked by more genes that may not be expressed in skin tone or curly hair.

Cover of the Spanish edition of the latest work by science columnist Carl Zimmer.

This is a book to learn about history and DNA. There are amusing passages that shatter beliefs or areas of ignorance that we had. thanks to scientific compilation and the author’s anecdotes we will know that there is more genetic variability Inside of Africa that among some African populations and Caucasian coming from other continents.

Indeed, one of the things that draws the most attention is the social and cultural aspect of genetic lineages, what we usually call ‘racial’, in a simplification that is not without connotations and consequences in the daily lives of citizens.

Zimmer assures that, “as the skin of hominids does not fossilizewe cannot say with certainty what the skin color of our ancestors were four million years ago.” However, “if our closest living primate relatives – gorillas and chimpanzees – are any guide, they probably had fair skin”.

Studies indicate that at some point, “perhaps two million years ago, our ancestors began to adapt to life on Earth.” african savannah and lost a lot of their body hair”. Once their skin was exposed to direct sunlight, the writer speculates, “it probably started to change color because ultraviolet rays could more easily reach the skin cells.”

So, he continues, “the damage they’ve done can cause skin cancer and also destroy an essential molecule in the skin called folate.” that’s why some mutations they would have added “more pigment in the skin”, in order to “protect our distant ancestors from this evil”.

However, “no one can be sure what color the skin of the first representatives of the homo sapiens”, says the promoter. “What is known is that the genetic variants who are behind the skin color they are scattered in many cities of the Earth and that everyone must have gone through a strong natural selection to survive near the Equator or in southern Africa, where the light is less intense”, he indicates.

A less bleak future than a century ago?

O diversity It is vegetable, animal and it also defines these hominids that we are. This is what guarantees our health and ecosystems. And this concept that circulates so much can be spoken with more propriety at the dawn of the 21st century, when seven decades of knowledge of the double helix of DNA (a discovery in 1953) are completed.

With that 1953 discovery also came a conflict over the Nobel Prize — in 1962, to Francis Crick and James Watson — which was withheld by a pioneering female scientist —rosalinda franklin—which is why Zimmer also explores the history of how social conditioning, discrimination, and the notion of gender have changed in each historical period.

In attempts to tame the wild and tame the unknown, many experiments have been done; among them, the kings began to marry between cousins

But before making the ethical and social aspect of genetics more complex, Zimmer takes us on a journey through the history of natural life, on a journey that talks about the genetic selection of plants or animals that have been domesticated to meet human needs.

Because researchers from all disciplines have been dabbling in far-fetched theories about heredity for centuries. For example, has anyone ever wondered how a pitted plum came to be? Or we knew it barley grains were not always soft so it was necessary to select the variants that served as an ingredient, since if they hardened they would no longer serve as food?

How many generations of sheep did it take before the sheep produced soft wool? here goes the spoilers: leave behind a season of rough wool, the amazing and North African Arabs introduced the Merinos.

Marry between princes of blue blood

In an attempt to tame the wild world and tame (or subdue) the unknown, many experiments have been done; among them, the kings began to marry between cousins, in the belief that this guaranteed a ‘blue blood’ offspring, different from the rest of the people. And it turns out they achieved the opposite effect: congenital diseases lasted forever and worsened in some royal bloodlines, and even the lack of healthy heirs led to wars and desperate solutions.

Thus, times of total opacity of knowledge passed, until the first eugenic experimentsin the United States at the beginning of the 20th century and, with them, the inspiration of National Socialism and the long period of supremacy.

Zimmer advances concepts of rewriting or genomic shortcuts, as well as CRISPR techniques (repetitive sequences present in the DNA of bacteria) so that the reader can approach them without setbacks or fear.

Finally, with everything learned, the reader will be able to learn more about genomic studies without getting lost in the first turns of the helical maze. Or we ask ourselves questions with a better objective: what can be expected from the rewriting of DNA?, for example.

Finally, after this compilation of hereditary studies, we will recognize part of our history and will be able to continue to investigate the possible applications that genetics offers to the personalized medicine of the future.

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