If you want to predict the color of something, you can talk about wavelengths of light. Light with a wavelength of around 460 nanometers is going to look blue. If you want to predict what something sounds like, frequencies can be a guide—a frequency of around 261 Hertz should sound like the musical note middle C.

Predicting smells is more difficult. While we know that many sulfur-containing molecules tend to fall somewhere in the ‘rotten egg’ or ‘skunky’ category, predicting other aromas based solely on a chemical structure is hard. Molecules with a similar chemical structure may smell quite different—while two molecules with very different chemical structures can smell the same.

This week in the journal Science, researchers describe developing an AI model that,  given the structure of a chemical compound, can roughly predict where it’s likely to fall on a map of odors. For example, is it grassy? Or more meaty? Perhaps floral?

Dr. Joel Mainland is one of the authors of that report. He’s a member of the Monell Chemical Senses Center and an adjunct associate professor in the department of neuroscience at the University of Pennsylvania in Philadelphia. Mainland joins Ira to talk about the mystery of odor, and his hope that odor maps like the one developed by the AI model could bring scientists closer to identifying the odor equivalent of the three primary colors—base notes that could be mixed and blended to create all other smells.

Juan Peña, 28, has worked in the fields since childhood, often exposing his body to extreme heat like the wave that hit the Midwest last week.

The heat can cause such deep pain in his whole body that he just wants to lie down, he said, as his body tells him he can’t take another day on the job. On those days, his only motivation to get out of bed is to earn dollars to send to his 10-month-old baby in Mexico.

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The Golden Lion Tamarin is a small, charismatic monkey with a mane of red fur that’s a local celebrity in Brazil’s Atlantic Forest. This pint-sized primate was on the brink of extinction back in the 1970s, with only about 200 left in the wild.

After decades of concentrated conservation efforts, an estimated 4,800 golden lion tamarins are now living in the wild. The multi-pronged effort involved reconnecting parts of the forest that had disappeared due to deforestation, vaccinating monkeys against yellow fever, and reintroducing zoo-bred primates to the wild.

Ira speaks to Carlos Ruiz Miranda, associate professor of conservation and behavior at Northern Rio de Janeiro State University in Campos dos Goytacazes, Brazil. Dr. Ruiz Miranda has worked on restoring golden lion tamarin populations for decades, and was involved in every facet of this effort. 

Last week, we briefly mentioned the sequencing and analysis of the human Y chromosome, which was recently reported in the journal Nature. It’s an important achievement—the small Y chromosome is filled with repeated segments of genetic code that make reconstructing the full sequence difficult. Think of trying to put together a jigsaw puzzle—the unique parts of the picture are easy, but areas with repeated colors, like sky or waves, are more challenging.    

In addition to the complete sequence of one individual’s Y, other researchers compared the Y chromosomes of 43 different individuals—and found that the structure of the chromosome can vary widely from one person to another.

The Y chromosome plays a key role in sex determination and sperm production, making it of interest to fertility researchers. It’s also linked to some diseases and health conditions.

Adam Phillippy, a senior investigator in the computational and statistical genomics branch of the National Human Genome Research Institute at the National Institutes of Health, and Kateryna Makova, a professor of biology at Penn State University, join Ira to talk about the challenges of sequencing the Y chromosome, and what doing so might mean for medical research.

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