What do broccoli, pigeons, frequent flyer miles, and mattresses have in common?
They are all subjects of “Surprisingly Awesome” podcasts.
I just listened to the one on broccoli, and I was really impressed. I love resources that help students see connections among topics. In just 41 minutes, the broccoli podcast touches on genetics, chemistry, sensory biology, natural selection, selective breeding, human evolution, and culture.
The podcast opens with the hosts swabbing their mouths to collect DNA, in an intriguing effort to find out more about their personal relationship with broccoli. But they don’t follow up on this tantalizing idea right away. Instead, they turn to an explanation of broccoli’s evolutionary history. Broccoli, collard greens, cabbage, kale, kohlrabi, Brussels sprouts, and cauliflower all belong to the same species, Brassica oleracea. Millions of years ago, Brassica oleracea was a weedy, stemmy plant with yellow flowers; in its original form, it doesn’t even look edible. But the species has lots of variation in the genes that tell it how to grow stems, leaves, and flowers. Some variations tell the plant to grow a super thick stem, as in kohlrabi; others tell the plant to make long, curly leaves, as in kale. Before recorded history, people were already selecting for these different variations.
This brings us to the ~15 minute mark and a couple of highly palatable commercials (narrated by the podcast hosts themselves). When we return to the podcast, the hosts introduce bitter-tasting chemical compounds, like the goitrin in broccoli (https://en.wikipedia.org/wiki/Goitrin). Our genes determine if we can taste it — that’s the connection with the DNA test at the start of the show. A goitrin solution has no flavor to non-tasters, who do not express the receptors for that chemical. But the same solution tastes awful to a taster. Like other bitter compounds, goitrin is a defense against herbivores — there’s the natural selection connection. Bitterness often indicates poison, so it’s no wonder people (especially kids) generally don’t like bitter foods. However, some bitter plants that taste bad are nutritious, so we cook them and add seasonings to make them taste better. From here on, the podcast is mostly devoted to the interplay of biology and culture, before returning to the awesomeness of broccoli.
I recommend this podcast as a relatable way to introduce students to selective breeding and natural selection. Instructors might want to assign the podcast as an at-home activity to inspire later in-class discussion about natural and artificial selection.
However, the hosts do commit a couple of linguistic crimes against evolution: When talking about plant defenses against herbivory, they say “The plants know they have something inside of them that animals want” and “They’re trying hard to keep animals away.” Anyone who has read my “Clever cockroaches” blog post will know that this shortcut — depicting evolution as a purposeful process — is one of my pet peeves because it undermines student learning about how evolution really works. On the plus side, statements like that can be valuable if we use them to point out what’s wrong with talking about evolution that way.