Hot Galaxy Cluster in Early Universe, Elephant Olfaction, Painted Lady Butterfly DNA Inversion

Three science stories unfold on NPR Shortwave: a galaxy cluster that formed about 12 billion years ago is surprisingly hot, challenging current models of early structure formation; elephants with nearly 2000 olfactory genes are shown to discriminate food quantities in a controlled maze, suggesting smell plays a role in foraging decisions; painted lady butterflies exhibit opposite migration paths in the northern and southern hemispheres, driven by a DNA inversion in migration-related genes, hinting at how a single species can split into two migratory populations. The episode weaves expert commentary with implications for understanding the universe’s youth and strategies for wildlife conservation.

Cosmic discovery: a hot young galaxy cluster

The episode begins with a discussion of a galaxy cluster formed about 12 billion years ago, a time when the universe was only about 13.8 billion years old. Contrary to expectations, this cluster is unusually hot, hotter than the sun’s surface, and it contains active galactic nuclei with supermassive black holes at their centers. Scientist Daji Zhou notes that such a hot cluster at this early epoch challenges prevailing theories about how large cosmic structures assemble and evolve. The host and guests compare the cluster’s early development to a cityscape that would resemble Las Vegas rather than a pastoral town, illustrating how these observations compel scientists to rethink models of cluster formation and growth. The team also emphasizes that this might be an extreme case requiring more data to determine how common such hot clusters are in the young universe.

"This galaxy cluster is popping." - Scott Detrow

Elephants and the sense of smell in foraging decisions

The program then turns to biology, focusing on elephants and their sense of smell. Elephants possess nearly 2000 olfactory genes, far more than humans and about twice as many as dogs, enabling a rich sense of smell at the trunk’s tip. A team led by Adrian Schrader at the University of Pretoria built a seven-foot-tall Y-shaped maze with two food-rich ends but a wall blocking direct view, making elephants rely on scent to choose the path with more food. The results show that elephants consistently picked the larger quantity unless the difference was under about 600 grams, roughly 6 to 10 trunkfuls of grass. External researcher Alvaro Lopez Que Goya acknowledges the remarkable smell discrimination, while cautioning that wild environments have far more scents than a controlled preserve. The findings point toward potential conservation strategies, such as masking crops with odors to deter elephant foraging in vulnerable areas.

"The elephant's ability to discriminate food quantities is remarkable" - Alvaro Lopez Que Goya

Migration barrier and DNA inversion in Painted Lady butterflies

Finally, the show covers butterfly migration, focusing on painted lady butterflies which travel the globe and display the longest migrations among butterflies. Researchers found that northern and southern hemisphere populations follow opposite migration routes, effectively creating a migration barrier at the equator. To understand the genetic basis, they analyzed DNA from over 300 butterflies across 38 countries. A striking discovery emerged: a large DNA segment in southern hemisphere butterflies was inverted relative to the northern population, and this segment contains migration-related genes. Aurora Garcia Barro explains that this could reflect a single species diverging into two populations due to different migratory pressures. The work, published in Nature Communications, underscores the importance of studying migration genetics to gauge species health and geography’s role in evolution. Aurora notes the implications for agricultural ecosystems, pollination, and broader biodiversity.

"A large chunk of DNA in the southern hemisphere butterflies was completely flipped" - Aurora Garcia Barro

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