Who we are and how we got here? What is our relationship to everyone else? How do we fit in this homogenized and interconnected world?

These are a few of the questions we have been asking for thousands of years. Many brilliant-and less brilliant-minds have tried to unwrap the bundle of complexity and sought to understand and answer the mystery of heredity and genetics.

Heredity is a very old idea. The ancients thought that there is something inside us that we have inherited from our ancestors and we pass down to our offsprings. The Greek philosophers had a variety of hypotheses about heredity. Hippocrates speculated that the material for heredity was produced by ‘’seeds” that were transferred to the offspring during the conception. Aristotle disagreed. He proposed that individual organisms begin when the fluids from the mother and the father are mixed. The maternal contribution, he thought, resided in the menstrual blood. It was an idea that would later influence the blood theory of heredity which appeals to those who pride themselves on having a noble or “blue blood” line.

We know a lot more about how heredity works now. We know that heredity is the genetic code you inherit in your DNA (deoxyribonucleic acid) from our parents. Each DNA molecule consists of four organic bases: adenine (A), guanine (G), cytosine (C) and thymine (T). The specific order of A, G, C and T within a DNA molecule is unique to each person, it determines your physical characteristics, along with your genetic disorders. Basically, hereditarians say, your DNA is what makes you, you!

But are we really just our genes? Or, as some claim, are we just the victims of our genes? Today we know that it is more complicated than that. We know about mitochondrial DNA. We know that DNA is modified by experience and by chance. We know that who we are depends on upbringing, education, lifestyle choices and environmental influence. Ongoing research continuously uncovers the role of epigenetics in a variety of human disorders and fatal diseases.

In his ambitious work, “She Has Her Mother’s Laugh: The Powers, Perversions, and Potential of Heredity”, Carl Zimmer, one of the best science writers today, delves deep into the complex history of heredity, weaving together history and philosophy, the science and the pseudoscience of heredity. It is a big book (656 pages) and it is full of fascinated stories of the well-known and famous, like Darwin, Mendel, Watson and Crick, and the less known but equally interesting, like Pearl Buck and Rosalind Franklin. He explores the breakthroughs that have changed what we know about heredity, the synthesis between heredity and evolution, the links between heredity and intelligence, the effects from the environment and how genes are switched on and off in different cells at different points of our development and life. He unfolds the new technologies, like CRISPR, which allows researchers to manipulate genes, or to correct genetic defects in patient cells, and the unintended consequences of gene-editing technique.

Carl Zimmer, who got his genome sequenced, also describes his personal journey into the story of heredity and his thoughts and the responsibility he felt knowing that his daughters would be inheriting a lot of his genes.

I loved this book