Many meat-eating mammals lack sweet tooth, study finds

March 26, 2012 By Amina Khan

For all their sharp teeth, many meat-eating mammals lack a sweet tooth, a genetic analysis of a dozen species has shown.

The study, published this month in the journal , shows that whose diets don't feature much in the way of sugar may lose the ability to it at all.

Study co-author Gary Beauchamp, director of the Monell Chemical Senses Center in Philadelphia, wasn't sure what he was expecting to find when he and his colleagues began looking at of a dozen different species to study their taste receptor genes. But he knew that cats are indifferent to sweet carbohydrates and lack a working copy of a key taste receptor gene called Tas1r2.

"At the time, the feeling was that the cat was a very unusual anomaly among mammals in that it didn't respond to sweets," Beauchamp said. "But we wondered if the cat represented something that had happened many times."

Using DNA samples mostly provided by the , the team from Monell and the University of Zurich examined taste in a dozen different mammals and found that seven species - including , Asian otters and spotted hyenas - lacked a properly functioning Tas1r2 receptor. All seven were meat- or fish-eaters.

The precise mutation in the Tas1r2 gene varied from species to species - an indication that the loss of a sweet tooth wasn't something that occurred just once in the mammalian family tree, but happened independently at different points in time.

Sweet wasn't the only taste to disappear. Sea lions also appeared to lack functioning genes for detecting the savory tastes known to humans as umami. So did dolphins, which also lack working genes to detect different types of bitter substances. That was surprising to Beauchamp, he said, since bitterness is a useful warning of the presence of poison.

Altogether, the findings "illustrate the fact that the sensory world of animals is highly attuned to their dietary patterns," Beauchamp said.

The loss of major taste receptors in sea lions and dolphins makes sense given that these species often gulp their food without chewing, he added.

A similar pattern appears to hold for vegetarian mammals. Beauchamp pointed to research showing that bamboo-eating pandas have a well-developed palate for sweets, but they lack working umami receptors to detect savory, "meaty" foods.

Thomas Finger, a neurobiologist at the University of Colorado's Rocky Mountain Taste and Smell Center in Aurora, who was not involved in the research, said the study was "pretty impressive." Now he wonders whether the lack of working sweet genes is a sign that there's an evolutionary cost to maintaining an essentially useless .

At the very least, he said, "it implies that as animals go to a more carnivorous diet, there's less and less advantage to it."

But Finger added one caveat. "They haven't tested the entire population" of these sweet-deprived species, he said. "If you looked in enough individuals you might find someone with the gene."

As for those cat owners who insist their feline loves chocolate or goes crazy for ice cream, Finger shrugged at humans' tendency to anthropomorphize their pets' tastes.

"Ice cream has a strong umami taste to it, so that's why your cat likes ice cream," he said. "It's the milk protein. We're very sensitive to sweets - but the cat doesn't get it."

Explore further: Study: Cats cannot taste sweets

Related Stories

Study: Cats cannot taste sweets

July 25, 2005

United States and British researchers announced Monday they have found a defective gene that makes it impossible for cats to taste sugar or other sweets.

Sour taste make you pucker? It may be in your genes

July 11, 2007

Scientists at the Monell Chemical Senses Center report that genes play a large role in determining individual differences in sour taste perception. The findings may help researchers identify the still-elusive taste receptor ...

Red pandas reveal an unexpected (artificial) sweet tooth

April 15, 2009

Researchers from the Monell Center report that the red panda is the first non-primate mammal to display a liking for the artificial sweetener aspartame. This unexpected affinity for an artificial sweetener may reflect structural ...

Recommended for you

Secrets of a heat-loving microbe unlocked

September 4, 2015

Scientists studying how a heat-loving microbe transfers its DNA from one generation to the next say it could further our understanding of an extraordinary superbug.

Plants also suffer from stress

September 4, 2015

High salt in soil dramatically stresses plant biology and reduces the growth and yield of crops. Now researchers have found specific proteins that allow plants to grow better under salt stress, and may help breed future generations ...

Ancient walnut forests linked to languages, trade routes

September 4, 2015

If Persian walnut trees could talk, they might tell of the numerous traders who moved along the Silk Roads' thousands of miles over thousands of years, carrying among their valuable merchandise the seeds that would turn into ...

Huddling rats behave as a 'super-organism'

September 3, 2015

Rodents huddle together when it is cold, they separate when it is warm, and at moderate temperatures they cycle between the warm center and the cold edges of the group. In a new study published in PLOS Computational Biology, ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.