Menus Subscribe Search

Follow us


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

November 25 • 4:00 PM

Is the Federal Reserve Bank of New York Doing Enough to Monitor Wall Street?

Bank President William Dudley says supervision is stronger than ever, but Democratic senators are unconvinced: “You need to fix it, Mr. Dudley, or we need to get someone who will.”


November 25 • 3:30 PM

Cultural Activities Help Seniors Retain Health Literacy

New research finds a link between the ability to process health-related information and regular attendance at movies, plays, and concerts.


November 25 • 12:00 PM

Why Did Doctors Stop Giving Women Orgasms?

You can thank the rise of the vibrator for that, according to technology historian Rachel Maines.


November 25 • 10:08 AM

Geography, Race, and LOLs

The online lexicon spreads through racial and ethnic groups as much as it does through geography and other traditional linguistic measures.


November 25 • 10:00 AM

If It’s Yellow, Seriously, Let It Mellow

If you actually care about water and the future of the species, you’ll think twice about flushing.


November 25 • 8:00 AM

Sometimes You Should Just Say No to Surgery

The introduction of national thyroid cancer screening in South Korea led to a 15-fold increase in diagnoses and a corresponding explosion of operations—but no difference in mortality rates. This is a prime example of over-diagnosis that’s contributing to bloated health care costs.



November 25 • 6:00 AM

The Long War Between Highbrow and Lowbrow

Despise The Avengers? Loathe the snobs who despise The Avengers? You’re not the first.


November 25 • 4:00 AM

Are Women More Open to Sex Than They Admit?

New research questions the conventional wisdom that men overestimate women’s level of sexual interest in them.


November 25 • 2:00 AM

The Geography of Innovation, or, Why Almost All Japanese People Hate Root Beer

Innovation is not a product of population density, but of something else entirely.


November 24 • 4:00 PM

Federal Reserve Announces Sweeping Review of Its Big Bank Oversight

The Federal Reserve Board wants to look at whether the views of examiners are being heard by higher-ups.



November 24 • 2:00 PM

That Catcalling Video Is a Reminder of Why Research Methods Are So Important

If your methods aren’t sound then neither are your findings.


November 24 • 12:00 PM

Yes, Republicans Can Still Win the White House

If the economy in 2016 is where it was in 2012 or better, Democrats will likely retain the White House. If not, well….


November 24 • 11:36 AM

Feeling—Not Being—Wealthy Cuts Support for Economic Redistribution

A new study suggests it’s relative wealth that leads people to oppose taxing the rich and giving to the poor.


November 24 • 10:00 AM

Why Are Patients Drawn to Certain Doctors?

We look for an emotional fit between our physicians and ourselves—and right now, that’s the best we can do.


November 24 • 8:00 AM

Why Do We Elect Corrupt Politicians?

Voters, it seems, are willing to forgive—over and over again—dishonest yet beloved politicians if they think the job is still getting done.



November 24 • 6:00 AM

They Steal Babies, Don’t They?

Ethiopia, the Hague, and the rise and fall of international adoption. An exclusive investigation of internal U.S. State Department documents describing how humanitarian adoptions metastasized into a mini-industry shot through with fraud, becoming a source of income for unscrupulous orphanages, government officials, and shady operators—and was then reined back in through diplomacy, regulation, and a brand-new federal law.


November 24 • 4:00 AM

Nudging Drivers, and Pedestrians, Into Better Behavior

Daniel Pink’s new series, Crowd Control, premieres tonight on the National Geographic Channel.


November 21 • 4:00 PM

Why Are America’s Poorest Toddlers Being Over-Prescribed ADHD Drugs?

Against all medical guidelines, children who are two and three years old are getting diagnosed with ADHD and treated with Adderall and other stimulants. It may be shocking, but it’s perfectly legal.



November 21 • 2:00 PM

The Best Moms Let Mess Happen

That’s the message of a Bounty commercial that reminds this sociologist of Sharon Hays’ work on “the ideology of intensive motherhood.”


November 21 • 12:00 PM

Eating Disorders Are Not Just for Women

Men, like women, are affected by our cultural preoccupation with thinness. And refusing to recognize that only makes things worse.


November 21 • 10:00 AM

Queens of the South

Inside Asheville, North Carolina’s 7th annual Miss Gay Latina pageant.


Follow us


Geography, Race, and LOLs

The online lexicon spreads through racial and ethnic groups as much as it does through geography and other traditional linguistic measures.

Feeling—Not Being—Wealthy Cuts Support for Economic Redistribution

A new study suggests it's relative wealth that leads people to oppose taxing the rich and giving to the poor.

Sufferers of Social Anxiety Disorder, Your Friends Like You

The first study of friends' perceptions suggest they know something's off with their pals but like them just the same.

Standing Up for My Group by Kicking Yours

Members of a minority ethnic group are less likely to express support for gay equality if they believe their own group suffers from discrimination.

How Old Brains Learn New Tricks

A new study shows that the neural plasticity needed for learning doesn't vanish as we age—it just moves.

The Big One

One in two United States senators and two in five House members who left office between 1998 and 2004 became lobbyists. November/December 2014

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