Pleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are

People do the strangest things, don’t they?

But no matter how normal you think you are, there are people out there who think you’re the oddball. From our diet to our habits to our beliefs, humanity is gloriously diverse.

How does this play out? Well, some people enjoy exotic foods and fine wine; others want nothing more than a plain hamburger and a Bud Light. Some people are vegetarians whereas others say that brussels sprouts taste like fart truffles. Some people stay thin throughout their lives; others feel their thighs widening just thinking about cheesecake. Some like to work out, and others would rather chill out.

We are collectively diverse in our habits as well. Some people wear sports jerseys and war paint to root for the home team; others would rather cosplay as a Borg at a Star Trek convention. Some live for a wild night on the town, and others prefer a night at the museum. Some people like to globe-trot; others won’t even venture out to World Market. Some people are fashionable, and others would wear down the hosts of What Not to Wear.

And what about our behavior? Alcohol and drugs have no pull over some, but others cannot escape their gravity. Some people are always honest, yet others will lie, cheat, and steal with no remorse. Some people are color-blind; others only want to see white. Some wouldn’t hurt a fly, while others fly off the handle. Some fight for war, others fight for peace.

The same is true of our romantic inclinations. Some people are faithful to their partners; others pretend to be. Some bank on good looks and money, while others are more invested in what’s below the surface. Some people want a soul mate to love for the rest of time; others would view that as a life sentence. Some people remember anniversaries; some people are forgetful.

And what of our very natures? Some people are kind, and others are mean. Some have boundless energy, while some seem lazy. Some are fearless, and some are scared of their own shadow. Some always see the glass as half full; others always see it as half empty and leaking.

And between all of these extremes are many people who fall somewhere in the middle. We are all flesh and blood—but what tremendous variability in how we live our lives! Nevertheless, I trust we have one thing in common: a desire to understand why each of us is so spectacularly different.

THROUGH THE AGES, people have watched as philosophers, theologians, self-help gurus, and Frasier Crane have attempted to tackle the mysteries of human behavior—often with limited success. But practical answers to the questions of why we are who we are and do the things we do are coming from an unexpected source: research laboratories.

Scientists have recently learned a great deal about us: deep, dark secrets that everyone needs to know. The better you know your true self, the easier it is to navigate life’s journey. And, by knowing what makes people tick, you will have a better understanding of those who are not like you.

All of us like to think that we march to the beat of our own drum. But science has revealed that the rhythm is played by percussionists we can’t see with the naked eye. We march through life believing that we’re the drummer—but the shocking evidence reveals this is an illusion. The truth is that there are hidden forces orchestrating our each and every move.

To illustrate this point, let’s consider one of my personal quirks: my distaste for vegetables like broccoli. I’ve always hated broccoli because it tastes so bitter to me; the smell of it cooking can make me gag. My wife, however, eats a lot of it. Willingly! What’s the difference between us? A clue comes from how our children responded to broccoli as infants: My son liked it, but my daughter reacted as if we were trying to poison her. We did not teach our children to love or loathe broccoli; they came to us this way, suggesting that this behavior is written in our DNA (we’ll spell out how this works in Chapter 2).

Let the ramifications of that sink in a minute: The genes in our DNA have a say in whether or not we like something. I’m vindicated! My aversion to broccoli is not my fault, and I should stop apologizing for it because I had no say in which genes I acquired.

If we’re not in control of something as basic as our personal tastes, what other things about us are beyond our command? In these pages, I set out on a quest to see how much genes contribute to our behavior. As we’ll see, DNA presides over much more than our physical attributes like eye color and whether we’re born with hands. It can also influence what we do with our lives, how quickly we lose our temper, whether we crave alcohol, how much we eat, who we fall for, and whether we like to jump out of perfectly good airplanes.

DNA is often referred to as the “blueprint of life” because it contains the instructions to build an organism. When it comes to building most people, DNA engineers the biological equivalent of a humble abode—although some folks get a mansion while others receive what we’ll call a fixer-upper. And then some seem to be constructed from the blueprints of the Death Star.

But surely, we are more than a pile of genes, right? Your relatives, for example, share a lot of your DNA, but you can all be surprisingly different. Even identical twins, who are essentially genetic clones that share 100 percent of their genes, often diverge in their appearance and behavior. The home-remodeling TV show Property Brothers is hosted by identical twins, but they are not exactly the same. One is a quarter inch taller than the other. One is obsessed with fashion and enjoys wearing suits, while the other dresses casually. One enjoys hammering out the business details; the other prefers to swing a hammer. One is a conscious eater while the other has a relaxed approach to diet. These differences suggest that genes build a house but something else makes it a home. In this book, we’ll take a look at the factors in our environment that can affect how our genes work, as well as how the environment may alter our DNA in ways that might be passed on to future generations. The means by which the outside world interplays with our genes is a new field of study known as epigenetics.

Epigenetics can have a tremendous impact on our behavior—and, remarkably, its effects on our DNA begin before we’re born. For example, exposure to nicotine or other drugs may chemically alter genes in the sperm of a father-to-be. What a mother does during pregnancy can also introduce lifelong changes onto the baby’s DNA. Epigenetics may play a wide-ranging role in obesity, depression, anxiety, intellectual ability, and more. Scientists are discovering how stress, abuse, poverty, and neglect can scar a victim’s DNA and adversely affect behavior for multiple generations. These astonishing findings in epigenetics constitute another hidden force directing our behavior, over which we have also had zero control.

In addition to our own genes, scientists have recently recognized that microscopic invaders bring a massive repository of genes into our bodies that are likely to shape our behavior as well. Ever hear of a microbiome? Well, pull up a stool and pay attention, because we’re going to learn all about it. The first microbial stowaways to set up camp in our gut came from our mother. We pick up more microbes from our food, pets, and other people as we age. New studies are revealing that the trillions of microbes teeming inside our guts may exert an influence on our food cravings, mood, personality, and more. For example, scientists can make a normally perky mouse gloomy by replacing its intestinal bacteria with microbes taken from a person suffering from depression. We’ll examine how the Western diet many of us enjoy radically changes the composition of gut bacteria, leading some to speculate that it could be a contributing factor to health problems like allergies, depression, and irritable bowel syndrome, which are more common in affluent countries.

There is also a one in four chance that a common parasite transmitted by cats—the parasite that we study in my laboratory—might have hijacked your brain, dampening your cognitive abilities and predisposing you to addiction, rage disorder, and neuroticism.

We’ll discuss emerging evidence suggesting that all of these tiny microbes are affecting our behavior for their benefit, making us wonder yet again if we are really in full control of our actions.

WORKING IN THE BIOLOGICAL SCIENCES for the past 25 years has provided me with a unique perspective on how life truly operates. My research into the hidden forces underlying our behavior has convinced me that almost everything we think we know about ourselves is wrong. And we are paying dearly for it. Our false sense of self hurts our personal, professional, and social lives. Our collective misunderstanding of human behavior impedes progress and adversely affects education, mental health, our justice system, and global politics. Exposing these hidden forces provides important new insights into our behavior, as well as a better understanding of people who do things we would never dream of doing.

In the upcoming chapters, we will take a closer look at just how much—or really, how little—control we have over our actions. This knowledge will help us better ourselves, and has the power to change our behavior in ways that will lead to a happier and healthier world. We’ll review the biological reasons underlying obesity, depression, and addiction, and how that knowledge is paving the way toward better treatments for these conditions. We’ll learn the real reasons why some people become aggressive or murderous, revealing potential ways to prevent these hideous behaviors from occurring. We’ll also explore what science is teaching us about love and attraction, and how these lessons can improve our relationships. And finally, we’ll peer into the psychology of our beliefs, including our political differences, in hopes that we can understand what leads us to act with blind faith, rather than insightful reason.

I can’t wait to tell you about you! But before we dive into humanity’s wildly diverse spread of behaviors, we’ll need to understand the hidden forces working behind the scenes to animate us. So let’s begin our journey by meeting our maker.