Humans tend to eat food that tastes good for them but it appears that this does not apply to penguins. Findings of a new study has found that these flightless aquatic birds lost three of the basic vertebrate tastes over 20 million years ago and were not able to regain them.

The research, which was published in the Current Biology on Feb. 16, has revealed that while penguins are capable of detecting sour and salty tastes, they do not have the genes needed to encode three of the five basic vertebrate tastes namely sweet, bitter and the savory, meat taste otherwise known as umami.

Huabin Zhao, from the College of Life Sciences at the Wuhan University in China, and colleagues look at the sequenced genomes of emperor penguins, Adelie penguins and 14 other species of birds and found that penguins do not have some of the basic taste genes.

They also found that unlike other birds such as chickens, Amazon parrots and finches that lost only their ability to taste sweet flavors, penguins lost their ability to detect bitter and umami tastes.

"Based on genome and relevant gene sequences, we infer that the sweet, umami, and bitter tastes have been lost in all penguins, an order of aquatic flightless birds originating and still occupying the coldest ecological niche on Earth, the Antarctic," the researchers wrote.

Study researcher Jianzhi Zhang, from the Department of Ecology and Evolutionary Biology at the University of Michigan, said that the loss of the umami taste in penguins is particularly perplexing because these birds are fish eaters. He noted that because penguins eat fish, they should have the umami receptor genes.

The researchers said that while they do not have a good explanation for this puzzling case of penguin taste, they have some ideas. Zhang said that the sensory changes may have been linked with ancient climate-cooling event that occurred in Antarctica where the birds originated.

His main hypothesis is that the genes were lost when the cold Antarctic temperatures interfered with the penguin's taste perception.

Although penguins evolved in the chilly Antarctic, many of this bird's species have already spread out to warmer climates. The researchers, however, said that the animal's movement to other regions did not regain their receptor genes for the three basic tastes.

"If ancestral penguins had lost the receptor genes for the three tastes while in the Antarctic, the genes and tastes cannot be regained even when some migrated away," Zhang said.