She Has Her Mother's Laugh

She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity
© 2018 Carl Zimmer
672 pages

Overhearing discussion of heredity a few hundred years ago would have meant only one thing:  being in the presence of noblemen, who stood to inherit their fathers' titles, lands, rights, and responsibilities.  Heredity quickly became a scientific concept,  and is now more commonly associated with biology than law, but genes aren't all we inherit. She Has Her Mother's Laugh is a meaty exploration of the history and present tracking of inheritance, genetic and otherwise.

Much of the book is a history of attempts to figure out heridity, beginning with mental impairment and the suspicion that it was something which could be passed down from generation to generation. This came of age when interest in biological inheritance was white-hot: Darwin and Huxley were at work, and various animal fanciers were creating ever-more elaborate breeds of pigeons and the like by monitoring traits from generation to generation and promoting the birth of different  variants.  It wasn't at all difficult for people to decide that imbecility was a distinct trait which could be controlled against, if all its present carriers were prevented from reproducing. This 'effort' was initially conceived as sterilization, but in the 1940s those efforts took on ghastly and murderous proportions Hitler's regime.

Aside from the outstandingly massive moral problems of controlling other people, including their ability to beget life,  there's also the scientific problem that "imbecility" is not one thing, created  by one trait. Mental impairments are diverse, and stem from all manner of biological hiccoughs. Many people in the Victorian age who were 'imbeciles' merely suffered from a metabolic disruption: they were unable to process a substance common in foodstuffs, and ingesting it slowly poisoned them, giving their skin an odd hue and eroding their mental faculties.  Children who were diagnosed early with this syndrome could be put on an appropriate diet, and be perfectly healthy members of society. Biology is chemistry in action, but the genes aren't the only chemicals in the solutions: they're constantly interacting with the substances of their mother's body, or the outside environment. Even if eugenicists had won, we would still have sick and infirm people, because there are so many variables. 

Other 'inheritance' issues are similarly problematic.  Take race, for instance; the human eye might look at a Norwegian, a Nigerian, and a Chinese citizen and declare them to be three obviously different kinds of people, but if that same eye were to look at their genes it would be unable to tell much of a difference beyond ordinary individual distinctions. Humans, for all our passionate in-grouping and out-grouping,  are far more alike than we are different -- biologically.  That doesn't mean our in-grouping and out-going is irrelevant; it  probably won't ever go away, because crucial to understanding human inheritance is realizing we are fundamentally cultural creatures. We don't come out of the womb sniffing wine and venturing opinions about the ballet, but we're as hungry for teaching as we are for food. When compared to chimpanzee juveniles, human youths are far more imitative.   Heredity cannot only apply to genes, or even biology (we also inherit bacteria from our parents):  it has to apply to culture, as well,

Zimmer also includes a chapter on CRISPR, and the admittedly scary potential that puts in our hands. Yes, we can eradicate genetic disease. We  can also turn our children into gross experiments, tinkering with their bodies to produce barbies or ubermensch. Society needs to think long and hard about the implications.

She Has Her Mother's Laugh is a steak of a book, of obvious interest to anyone with an appetite for human biology.

Some of my highlights:
"In Morgan’s own research on flies, he had learned to respect the power of the environment. His students discovered one strain of flies that developed normally if they were born in the summer but tended to sprout extra legs if they were born in the winter. It turned out that the researchers could get the same outcomes in their lab simply by changing the temperature in which they reared the fly eggs. It was thus meaningless to talk about the effect of their mutation without taking into account their environment."

“It was my child who taught me to understand so clearly all people are equal in their humanity and that all have the same human rights,” Pearl [Buck] wrote. “Though the mind has gone away, though he cannot speak or communicate with anyone, the human stuff is there, and he belongs to the human family.”

"To eliminate imperfection would demand eliminating humanity itself."

"We were three people of African, Asian, and European descent from three corners of the world. Three races, some might say. And yet we shared far more than what set us apart."

"Textbooks say that the human body has about two hundred cell types, but recent studies have rendered that figure a laughable understatement. No one can say how many cell types there are, because the more scientists examine cells the more they break down into more typed. Immune cells may all carry out the same mission to save us from pathogens and cancer, but they are an army with hundreds of divisions. All our cell types are seperate branches on the body's genealogical tree, like rival dynasties descended from a first monarch."