Why Scientists Once Used Taste Tests as Paternity Tests

It’s not unusual for families to bicker about food around the dinner table. When I was growing up, my younger brother and my parents quarreled about his distaste for bitter, leafy greens and vegetables. One day, when my mother asked why he wouldn’t finish his broccoli, he earnestly replied: “Because my body is rejecting it.”

My family still quotes his answer. But there may be a scientific basis to his reasoning: Some people are more sensitive to certain tastes, particularly bitterness, and can’t stand the sharpness of, say, brussels sprouts. The compound phenylthiocarbamide (PTC) is responsible for people’s varying sensitivity to bitterness. And while some people taste PTC intensely, others don’t notice it at all.

Since its discovery in the 1930s, scientists have believed that PTC-sensitivity is inheritable. In fact, the ability to taste PTC was once thought to have such a strong genetic link that it was used in paternity tests.

In 1931, a chemist named Albert Fox poured a powdered form of PTC into a bottle. Inadvertently, he created a PTC cloud that permeated the lab. He didn’t notice anything unusual, until a colleague, C.R. Noller, began griping about how terribly bitter the stuff tasted. Fox was baffled, and even put PTC crystals on his tongue and pronounced them tasteless. Meanwhile, Noller tasted a few of the crystals and nearly spat them out.

The two chemists then asked friends and other colleagues to test the PTC. Some people, like Fox, thought it tasted like nothing. Others found it extremely bitter, like Noller. By testing a large number of people across different backgrounds, sexes, and ages, Fox overwhelmingly discovered that one subsection of people could taste the PTC compound, no matter the concentration. He called these people “tasters.” People who couldn’t taste it became “taste blind” or “nontasters.”

Fox was then able to predict whether someone would taste PTC by observing how their families reacted to it. Soon, Fox’s work caught the attention of other scientists, such as L.H. Snyder, who concluded that a person’s status as a nontaster is carried by a recessive allele. In 1932, the botanist Albert Blakeslee conducted the first large-scale study of PTC inheritance. Their conclusion? Being a taster was genetic.

That’s how the PTC taste test began to be used as part of paternity tests in the mid-20th century, along with blood testing. (This was before the days of widespread DNA analysis.) In a 1951 study, Hugo M. Cardullo and L. Emmett Holt, Jr. declared that “it is demonstrated that the ability to taste or not to taste this compound is demonstrable in early infancy and it is suggested that such data can be profitably employed in cases of doubtful paternity.” Throughout the 1950s, the PTC test was used to help determine paternity. The belief was that if you and your father differed significantly on your ability to taste PTC, you probably weren’t related.

As The Wall Street Journal noted in 2003, PTC tests were often used to show basic principles of genetics in high-school classes. These days, a PTC test involves placing a strip of paper with small amounts of the substance on the tongue and observing what you taste (or don’t).

While the PTC gene is thought to constitute, at most, 85% of whether someone is a taster or a non-taster, other genes and environmental factors play a role. So PTC isn’t an entirely accurate determiner of paternity. According to a 2001 study, PTC taste blindness has been linked to thyroid disorders. Other studies have debated whether alcoholism is linked to PTC insensitivity. The work of Linda Bartoshuk in the 1990s also revealed that people who are especially sensitive to tastes such as bitterness and sourness are “supertasters,” or people who have a high density of taste buds on their tongues. Supertaster status is thought to be genetic, but only partially. What’s more, the exact way that PTC detection is inherited remains debated. It’s entirely possible that many PTC paternity tests from the ‘50s were inaccurate.

So my brother’s sensitivity to bitter foods may make him a supertaster, but his aversion to broccoli isn’t genetic. He isn’t so quick to spit them out anymore either—just the other day I saw him eating a salad. When I asked him if greens had grown on him, he scowled, just as he had at age seven, and clarified that he still didn’t like eating them. Now, he just knows he probably should.

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