Menus Subscribe Search
heredity

(PHOTO: DAVID HUNTLEY CREATIVE/SHUTTERSTOCK)

We Still Don’t Know Why We Look Like Our Parents

• August 23, 2013 • 6:00 AM

(PHOTO: DAVID HUNTLEY CREATIVE/SHUTTERSTOCK)

Genetics? Sure, but it’s not that simple.

Why do children resemble their parents? It’s a question that has intrigued people for millennia, and surprisingly, in spite of our cutting-edge biotechnology, scientists still don’t have an answer. But when they find one, it will have big implications for how we use genetics to personalize medicine and understand human behavior.

Today, we take it as given that children have inherited genes from their parents, but the idea that parents pass on genetic material was a late development in science. Until the 19th century, those who considered the issue generally figured that parents made their children by a process analogous to fermentation. In essence, family resemblance was the consequence of the unique brewing conditions created by each set of parents. René Descartes compared semen to the “scum formed on beer” that can be used to make the next batch. Families differed because some couples make ales, while others make lagers.

When the field of genetics began to take off during the early 20th century, scientists attacked the problem of heredity with increasingly powerful statistical tools. In 1918, the geneticist R.A. Fisher devised a way to tease apart the separate influences of genes and environment on hereditary traits, such as height, by using measurements of family resemblance. Amazingly, Fisher showed that you can estimate the effects of genes and environmental factors without ever identifying the actual genes or environmental factors involved. (In fact, scientists did not even know what a gene was back then.) Scientists improved on Fisher’s statistical approach over the years, and for more than half a century breeders have used these methods successfully to improve their crops and livestock.

Beware the oversimplified genetic just-so stories claiming that we are the way we are because of the “gene for X.”

But by itself, the mere knowledge that the differences between us are influenced by genes isn’t very satisfying. Rather than simply knowing that there is a genetic basis for male-pattern baldness or cancer, we want to know the identities of the actual genes involved so that we can study their biological role and come up with ways to prevent, treat, and even cure what ails us.

With the recent arrival of cheap technology for analyzing DNA, scientists had high hopes that we could, at long last, go out and find the actual differences in our DNA that account for the influence of heredity on our physical traits, our health, and even our behavior. The results that have come in over the past few years have been disappointing.

The problem: most of the genetic differences discovered have only a very small effect. And when you add up all those effects, the result can’t possibly explain the full influence of our genes on those traits. For example, researchers have identified hundreds of DNA differences between people that influence the very strongly heritable trait of human height, but the total effect of those differences added together explains only about 10 percent of the genetic influence on height. In other words, we still can’t explain why tall parents have tall children.

Scientists have named this discrepancy the “missing heritability,” and they’ve spent the last half-decade trying to find it. As researchers have wrestled with the case of the missing heritability, two clear lessons have emerged about our relationship with our genes.

First, scientists have confirmed that genes have a substantial influence on our physical traits, our health risks, and our behavior. Missing heritability could suggest that we’ve overestimated the role of genetics (a common criticism in debates over genetics and behavior in particular), and the question has prompted scientists to revisit how they measure heritability. New, independent measurements largely confirm the previous findings. This does not mean that environment plays no role (it clearly does), nor does it mean that we’re helpless when it comes to fixing negative genetic influences on health or behavior (we do this all the time, with things like eyeglasses, hearing aids, and drugs).

The second lesson is that the relationship between our genes and our selves is not as simple as many scientists had hoped. Many thought it would be straightforward to find most of the DNA differences that account for the influence of genetics on various traits, but that hope turned out to be too optimistic. The case of the missing heritability has revealed that many small genetic differences, rather than a few large ones, play the biggest role in human diversity.

Behavioral traits probably have even more intricate genetic underpinnings. As the authors of a recent study of the genetics of educational attainment warned, we need to beware the oversimplified genetic just-so stories claiming that we are the way we are because of the “gene for X.” They concluded that “the genetic architecture of complex behavioral traits is far more diffuse than that of complex physical traits.” Another recent study looking for genetic differences in a wide range of traits, from political orientation and gambling frequency to neuroticism, reported a similar conclusion, that generally “genes are connected to behavioral variation by lengthy, nonlinear, interactive causal chains.”

With modern genetics, we have the tools to better understand our relationship to our genes; we’re also beginning to understand just how subtle that relationship is.

Michael White
Michael White is a systems biologist at the Department of Genetics and the Center for Genome Sciences and Systems Biology at the Washington University School of Medicine in St. Louis, where he studies how DNA encodes information for gene regulation. He co-founded the online science pub The Finch and Pea. Follow him on Twitter @genologos.

More From Michael White

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

July 25 • 4:00 PM

Flying Blind: The View From 30,000 Feet Puts Everything in Perspective

Next time you find yourself in an airplane, consider keeping your phone turned off and the window open.


July 25 • 2:00 PM

Trophy Scarves: Race, Gender, and the Woman-as-Prop Trope

Social inequality unapologetically laid bare.


July 25 • 1:51 PM

Confusing Population Change With Migration

A lot of population change is baked into a region from migration that happened decades ago.


July 25 • 1:37 PM

Do Not Tell Your Kids That Eating Vegetables Will Make Them Stronger

Instead, hand them over in silence. Or, market them as the most delicious snack known to mankind.



July 25 • 11:07 AM

The West’s Groundwater Is Being Sucked Dry

Scientists were stunned to discover just how much groundwater has been lost from beneath the Colorado River over the past 10 years.


July 25 • 10:00 AM

Shelf Help: New Book Reviews in 100 Words or Less

What you need to know about Bad Feminist, XL Love, and The Birth of Korean Cool.



July 25 • 8:00 AM

The Consequences of Curing Childhood Cancer

The majority of American children with cancer will be cured, but it may leave them unable to have children of their own. Should preserving fertility in cancer survivors be a research priority?


July 25 • 6:00 AM

Men Find Caring, Understanding Responses Sexy. Women, Not So Much

For women looking to attract a man, there are advantages to being a caring conversationalist. But new research finds it doesn’t work the other way around.


July 25 • 4:00 AM

Arizona’s Double-Talk on Execution and Torture

The state is certain that Joseph Wood’s death was totally constitutional. But they’re looking into it.


July 24 • 4:00 PM

Overweight Americans Have the Lowest Risk of Premature Death

Why do we use the term “normal weight” when talking about BMI? What’s presented as normal certainly isn’t the norm, and it may not even be what’s most healthy.


July 24 • 2:00 PM

California’s Lax Policing of the Fracking Industry Has Put the Drought-Stricken State in a Terrible Situation

The state’s drought has forced farmers to rely on groundwater, even as aquifers have been intentionally polluted due to exemptions for the oil industry.


July 24 • 12:00 PM

What’s in a Name? The Problem With Washington’s Football Team

A senior advisor to the National Congress of American Indians once threw an embarrassing themed party that involved headdresses. He regrets that costume now, but knows his experience is one many others can relate to.


July 24 • 11:00 AM

How Wildlife Declines Are Leading to Slavery and Terrorism

As wildlife numbers dwindle, wildlife crimes are rising—and that’s fueling a raft of heinous crimes committed against humans.


July 24 • 10:58 AM

How the Supremes Pick Their Cases—and Why Obamacare Is Safe for Now

The opponents of Obamacare who went one for two in circuit court rulings earlier this week are unlikely to see their cases reach the Supreme Court.



July 24 • 9:48 AM

The People Who Are Scared of Dogs

While more people fear snakes or spiders, with dogs everywhere, cynophobia makes everyday public life a constant challenge.


July 24 • 8:00 AM

Newton’s Needle: On Scientific Self-Experimentation

It is all too easy to treat science as a platform that allows the observer to hover over the messiness of life, unobserved and untouched. But by remembering the role of the body in science, perhaps we humanize it as well.


July 24 • 6:00 AM

Commercializing the Counterculture: How the Summer Music Festival Went Mainstream

With painted Volkswagen buses, talk of “free love,” and other reminders of the Woodstock era replaced by advertising and corporate sponsorships, hippie culture may be dying, but a new subculture—a sort of purgatory between hipster and hippie—is on the rise.


July 24 • 5:00 AM

In Praise of Our Short Attention Spans

Maybe there’s a good reason why it seems like there’s been a decline in our our ability to concentrate for a prolonged period of time.


July 24 • 4:00 AM

How Stereotypes Take Shape

New research from Scotland finds they’re an unfortunate product of the way we process and share information.


July 23 • 4:00 PM

Who Doesn’t Like Atheists?

The Pew Research Center asked Americans of varying religious affiliations how they felt about each other.


July 23 • 2:00 PM

We Need to Start Tracking Patient Harm and Medical Mistakes Now

Top patient-safety experts call on Congress to step in and, among other steps, give the Centers for Disease Control and Prevention wider responsibility for measuring medical mistakes.


July 23 • 12:19 PM

How a CEO’s Fiery Battle Speeches Can Shape Ethical Behavior

CEO war speech might inspire ethical decisions internally and unethical ones among competing companies.


Follow us


Subscribe Now

Do Not Tell Your Kids That Eating Vegetables Will Make Them Stronger

Instead, hand them over in silence. Or, market them as the most delicious snack known to mankind.

The West’s Groundwater Is Being Sucked Dry

Scientists were stunned to discover just how much groundwater has been lost from beneath the Colorado River over the past 10 years.

How Wildlife Declines Are Leading to Slavery and Terrorism

As wildlife numbers dwindle, wildlife crimes are rising—and that's fueling a raft of heinous crimes committed against humans.

How a CEO’s Fiery Battle Speeches Can Shape Ethical Behavior

CEO war speech might inspire ethical decisions internally and unethical ones among competing companies.

Modern Technology Still Doesn’t Protect Americans From Deadly Landslides

No landslide monitoring or warning systems are being used to protect vulnerable communities.

The Big One

Today, the United States produces less than two percent of the clothing purchased by Americans. In 1990, it produced nearly 50 percent. July/August 2014

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.