genetics – Ink-Stained Wretches

BY HELEN CURRIE FOSTER

April 1! It’s spring, with a riot of bluebonnets this year.

Plus paintbrush! Winecup! Verbena! Prairie celestials (so lovely)!

And within the fence, safe from our marauding burros, the roses are opening their petals and sharing their beauty. Humans have been growing and hybridizing roses for millenia. I favor those with deep rose fragrance. This year the sniff prize goes to Madame Isaac Pereire,

but Zephirine Drouhine is a strong contender as well—sweet perfume, but no thorns!

Blooming with pride are Cramoisi Superieur, fun to pronounce, and dainty little Perle d’or, below.

Yes, the French have been busy. But I’m waiting on the spectacular Star of the Republic, which is covered with buds that will become exquisite cream and pink roses, and is almost as tall as Texas.

Thanks for human ingenuity and the deep love of beauty and fragrance that resulted in these roses. We humans are so able to produce beauty—and yet we mystery readers and writers know how gripped we are by the companion question: why do humans commit the primal sin of murder?

I’ve been reading a riveting book called How the Mind Changed, A Human History of Our Evolving Brain (2022), by neuroscientist Joseph Jebelli, who studies the genetic history of the human brain. I’ve had to put stickers and checks on so many pages!

Jebelli says that, starting about 7 million years (or 230,000 generations) ago, when humans split from chimps, our brains were only 350 cm3 big. Then 3.5 million years ago, when our ancestor Lucy came along, we got a new uniquely human gene that gave us a folding neocortex and nearly doubled our brain size to 650 cm3.

Later, he says, our brains bloomed to 900 cm3, when we began cooking (maybe 2.7 million years ago), then to 1000 cm3, about 2.5 million years ago, then to 1500 cm3 500,000 years ago, and then grew another 25% by the time, 300,000-400,000 years ago, when Homo sapiens appeared.

Later research shows—the bigger the brain, the bigger the social group. Id., 69.

And lucky Homo sapiens came along when our planet was in extreme ecological instability: “African megadroughts depleted the land’s fresh water; vanishing grasslands diminished the number of animals available…” Homo sapiens spread across the planet, interbreeding along the way with the Neanderthals (who went extinct around 40,000 years ago), and the Denisovans, Neanderthal cousins from Asia. Most humans outside Africa carry around 2 percent Neanderthal-derived DNA while today humans in Papua New Guinea and Australia possess up to 6% Denisovan DNA.

Now we have tools of advanced microscopy and molecular genetics to use “the mosaic of neurons, the constellation of synapses and the tributaries of molecules to learn the age of the brain and the transformations it has seen.” Îd., 21.

But it’s Jebelli’s discussion of brain research on “fair play” that I find most fascinating – whether the experiment uses rats, vampire bats, or humans. “Our minds intuitively draw a distinction between unfair equality (all students receiving the same…grades regardless of merit) and fair inequality (the doctor earning more than the cleaner). When push comes to shove, humans nearly always prefer fair inequality to unfair equality.” Jebelli goes on to explain that when we humans engage in fair play, we experience a surge of neural activity in our brain’s reward centers, releasing dopamine, oxytocin, serotonin and endorphins. Id., 68.

Watch out: scientists are identifying gene mutations that explain amazing things. “Non-monogamous brains tend to have a special kind of dopamine receptor gene called DRD4, which is linked to promiscuity and infidelity.” Id., 78. Use that in a plot, mystery-writers!

But I was thrilled by the focus on the link between strong imagination and intelligence in our “default network, a brain system that participates in daydreaming, mind wandering, reflective thinking and imagining the future….People who engage in these cognitive practices…have greater access to the states of mind necessary to solve complex problems.” Id., 115. Jebelli says our default networks are only active when we’re not focused on a task, “when the brain is cycling through thoughts not associated with the immediate environment.” In other words, the default network contrasts with our executive control network. Jebelli makes another leap: compassion also stimulates the default network. “Compassion requires imagination. ‘Climb into his skin and walk around in it,’ Atticus tells Scout.” But imagination also requires compassion. Id., 119.

Why has this book grabbed me? As a mystery writer I wrestle with why some humans will run into the street to save a child from a bus, and some will just watch; and why and how some humans invent gripping new imaginative worlds (Lord of the Rings, Harry Potter, Slough House, Yoknapatawpha County, the Forest of Arden, Hat Creek and the saga of Lonesome Dove) that tell of human struggles and victories, tragedies and comedies. Yes, writers who stimulate our “default networks”!

So you might like to take a peek at How the Mind Changed—check out the chapter on that age-old conundrum––what is consciousness? And the chapter on different minds, or neurodiversity, including genetic components. And the chapter on the new field of neurocriminology: what makes humans commit crimes? Which brain regions are responsible for violence? One possibility—it’s an area of the hypothalamus called the ventromedial hypothalamus, “an ancient brain region that has been conserved throughout mammalian evolution.” Yikes!

As Jebelli notes, plots will abound from this inquiry, this research. As always, inquiring minds want to know.

Meanwhile, it’s April! So let us now praise Geoffrey Chaucer – whose compassion and imagination gave us “Whan that April with his showres soote The droughte of March hath perced to the roote, And bathed every veine in swich licour, Of which vertu engendred is the flowr…”

And further to celebrate—Book 9 of my Alice MacDonald Greer legal thriller series has gone off for copy-edit. Yes, again the primal crime has been committed…!

by Helen Currie Foster

Okay—Mom Genes is such a great title, it couldn’t not be used. But Abigail Tucker’s new book of that title doesn’t focus just on moms. Tucker, a New York Times best-selling science writer, dives deep into the burgeoning science examining parental behavior—genetic? hormonal? learned?

And you writers may find it a rich source for potential plots.

Moms will recognize Tucker’s description of the weird sensation of being kidnapped, of feeling like victims of an Invasion of the Body Snatchers. Not feeling quite yourself? In the first of a series of jaw-dropping recent research findings, Tucker reports, “Our children colonize our lungs, spleens, kidneys, thyroids, skin”—and brains. Far from being that familiar image of the one-way street, with mother’s blood, nutrients and even cells flowing into the fetus, the fetus also sends its own fetal cells into the mother. It’s “fetal microchimerism.” No wonder a burgeoning mom feels…she’s changed.

Tucker doesn’t dodge painful issues of maternal and paternal favoritism. “Some 80 percent of us allegedly … prefer one of our children to the others, and more than half of parents demonstrate so-called differential treatment toward various progeny.” The most striking predictor? “Moms appear to dote on their cutest kids.” Apparently “the components of infant attractiveness…are rigid and globally constant,” including big eyes, large forehead, small chin, and chubby cheeks. Tucker says this preference extends to nearly all baby mammals.

But dads apparently outperform moms on “child facial resemblance determination” – i.e., dads are more skilled at noticing whether a child looks like them. Indeed, one Senegal study found “kids grow up bigger and are better fed if they look and in fact smell more like their dads.” A different kind of favoritism…favoring the child which dad feels sure is his.

Jane Austen knew this. You remember that Mr. and Mrs. Bennet, the parents in Pride and Prejudice, have different favorites? Mrs. Bennet favors beautiful Jane; Mr. Bennet favors sensible Lizzy (Elizabeth). Mrs. Bennet scolds her husband: “Lizzy is not a bit better than the others; and I am sure she is not half so handsome as Jane, nor half so good-humoured as Lydia. But you are always giving her the preference.”

Humans share mothering tendencies across species. Will you recognize yourself if I mention “left-handed cradling bias”? In a “near-universal” mothering behavior, “Something like 80 percent of right-handed women and, remarkably, almost as many left-handed women hold their babies automatically on the left.” Check out many paintings of the Madonna, suggests Tucker. This “lefty” preference extends to other mammals. Why? It may allow the infant to “view the more expressive left side of the maternal face.”

Tucker points out it’s not all about genes. Life experience also affects maternal behavior. She describes studies of new monkey mothers showing that, of those roughly treated by their mothers, “more than half of the maltreated monkeys became abusive mothers. All the well-tended infants matured as competent mothers.” But when the scientists swapped some babies, so the abusive monkey moms took charge of the offspring of outstanding monkey moms, “the monkeys grew up to match the behaviors of their adoptive mothers, not their biological mothers.”

Here’s another potential genetic component. Canadian scientist Frances Champagne wondered why mother lab rats from the same genetic strain, living under identical conditions, engaged in different “licking/grooming” of their babies. When Champagne swapped the rat babies, so high-licking moms raised the babies of low-licking moms, the babies of below-average lickers followed in their adoptive mom’s footsteps. Then other scientists found they could program a baby rat’s future licking behavior by stroking it with a tiny paintbrush. “The physicality of getting licked somehow shaped the females’ instincts and behavior.” According to Champagne, “I wanted to show that the care you receive leads to epigenetic changes in infancy, and that this could replicate.” Epigenetics focuses on whether and how bits of genetic code may be “expressed.” Champagne found well-licked baby rats “were more likely to express their genes for certain estrogen receptors…” which made them more likely to express genes for oxytocin receptors and to grow more oxytocin neurons in their brains.

Fascinating research discusses how different bits of our genes “express” themselves, particularly in response to hormones. For instance, various sorts of stress can result in hormonal effects on gene expression: “Physiological changes that affect mRNA stability occur during development, nutritional stress, hypoxia, inflammation, cancer, and aging.”

The notion that our genes are static? Maybe not!

So…parental behavior factors include genes plus life experience with hormones kicking into action to affect gene expression.

Back to favoritism! Harry Potter? Reluctant adoptive parent Mrs. Dursley can’t abide her own sister’s son. The internet is full of books and studies on why parents have favorites and how favorites impact families, including impact on sibling rivalry.

Being a favorite can be dangerous, as Joseph learned. “Now Israel loved Joseph more than any other of his children…But when his brothers saw that their father loved him more than all his brothers, they hated him….” (Genesis 37.)

And I haven’t touched on what Tucker calls the “murderous tendencies of mothers,” citing Sarah Blaffer Hrdy’s theories on infanticide in Mother Nature.

Tucker’s final chapters look at the impact of our own stressful society on parents. “Social-support deficits and perinatal depression are intimately linked.” Tucker reports that compared to Dutch mothers, American mothers appeared comparatively quite miserable, with high levels of unhappiness and worry, because they don’t get enough support in their health care or workplace. To transform this problem “would involve taking on some of the most grinding and deadlocked political issues of our day: not only income inequality, but also health care, education, and other topics that have consistently stumped our government,” including racism (citing pregnant Black women’s higher blood pressure and elevated risks of prenatal diabetes, preterm delivery and death).

Tucker visited Erin Kinnally, a scientist at the UC Davis California National Primate Research Center. “Kinnally rattles off the factors that can shape primate moms…age, number of births, genetics, her own mother’s rearing history, the baby’s sex and other characteristics, access to food and shelter and sundry other environmental factors.” But the most potent force is “social chemistry.” The low-ranking macaque moms at the primate center “have weaker immune system and other distinct traits…the lowest ranking moms had four times the amount of stress hormones in their blood.” “Low-ranking [macaque] moms grasp that they have to be vigilant at all times. Fascinating studies have shown that these moms are much more likely to try to shush their infants’ cries when higher-ranked animals are around, for fear that the fussing will draw unwanted attention and attacks.”

Hormonal impact? Stress can mean a baby gets more cortisol in breast milk. In monkeys, “these high-cortisol babies grow unusually quickly, ‘prioritizing’ growth instead of social exploration…”

Tucker, like Bill Bryson in The Body, respects her readers enough to include a serious index. Hers is excellent: for her assertions in each chapter, she includes detailed links to the research studies involved.

We’re all from families; we’re all affected by our genes and our experiences, by how we were parented (and, indeed, how those who parented us were parented, and so on back up the long chain of humanity). Mom Genes confirms what writers already suspect: plots abound!

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Helen Currie Foster lives north of Dripping Springs, Texas, supervised by three burros. She writes the Alice MacDonald Greer Mystery series. Ghost Daughter, Book 7 of the series, was published June 15, 2021. Helen’s active with Austin Shakespeare and Sisters in Crime – Heart of Texas chapter. Find out more at www.helencurriefoster.com.