Your sense of smell may not be as good as that of your ancestors.

A new study that tested volunteers' perceptions of various smells — including underarm odor — adds to growing evidence that people's sense of smell is declining, little by little.

"Genome-wide scans identified novel genetic variants associated with odor perception, providing support for the hypothesis," the researchers said in a news release from the journal PLOS Genetics. The study was published there Feb. 3.

Individuals experience smells differently, and the same scent may be pleasant, too intense or undetectable to various people. By combining differences in scent perception and people's genetics, scientists can identify the role of various scent receptors.

In this study, researchers in the United States and China analyzed the genomes of 1,000 Han Chinese people. They were looking for genetic variations associated with how individuals perceived 10 scents. The investigators then repeated the experiment for six odors in an ethnically diverse group of 364 people.

From these experiments, they pinpointed two new scent receptors — one that detects a synthetic musk used in fragrances and another for a compound in body odor.

Study participants had different versions of the receptor genes for musk and underarm odor, and those variations affected how they perceived the scents.

These findings and previous research show that people with ancestral versions of the brain's scent receptors tend to find the corresponding odor more intense. Ancestral versions are those shared with non-human primates, the team explained.

The researchers, led by Joel Mainland of the Monell Chemical Senses Center in Philadelphia and Sijia Wang of the Chinese Academy of Sciences in Shanghai, said it all supports the theory that our sense of smell has weakened over time due to gene changes.

This study also confirmed three reported links between genes for scent receptors and specific odors. Those earlier studies included primarily Caucasian participants. The new findings from East Asian and diverse groups suggest that genetics underlying the ability to detect odors are constant across people of different backgrounds.