What Did Insects Evolve From and More Questions From Our Readers

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Illustration by Sarah Wilkins

What did insects evolve from?

Nathan McIntosh, Rock Hill, South Carolina

They were once thought to be most closely related to the Myriapoda (centipedes, millipedes and relatives), because of their presumed structural similarity. Most molecular data now indicate that they derive from a branch of the Crustacea and probably originated in an aquatic realm, likely fresh water.

- Conrad Labandeira, curator of fossil arthropods, National Museum of Natural History

If the universe is expanding and everything in it is traveling at the same speed, why would galaxies collide, as the Milky Way and Andromeda are projected to do?

James Rains, Concord, California

There’s a competition between the expansion of the universe and the gravitational attraction between galaxies. For galaxies separated by very large distances, the expansion of the universe dominates. But when galaxies are relatively close—such as the Milky Way and Andromeda—we expect that their mutual gravitational attraction will draw them to collide.

- Paul Torrey, astronomer, Harvard-Smithsonian Center for Astrophysics

Petroglyphs seem to appear all over the globe. Does this art form date back to a specific time and place, or did it develop independently at several times and places?

Mike Parker, Dimondale, Michigan

Both, you could say. Petroglyphs, or marks carved into rock, appeared as long as 70,000 years ago at several distant sites and morphed gradually into images about 35,000 years ago. Undoubtedly somebody, somewhere was the first to carve petroglyphs, but no one today can say who or where. On the other hand, as spreading populations carried the practice around the world, it may have ceased in certain times and places for religious or other reasons, only to be independently restarted hundreds of years later.

- William Fitzhugh, anthropologist, National Museum of Natural History

What would happen if the volcano under Yellowstone National Park erupted?

Calvin VanDee, Ithaca, New York

Most likely, there would be “small” hydrothermal eruptions of the reservoirs of steam or hot water that underlie the park’s geysers, hot springs and fumaroles; those explosions could produce craters more than a kilometer wide. The most likely volcanic eruption would be lava flows of either rhyolite or basalt; the former might also produce ash and pumice. But keep in mind that the probability of such an eruption in any given century is exceedingly low.

- Ed Venzke, geologist, Global Volcanism Program, National Museum of Natural History

Do animals have taste buds?

Irene Neely, Port Jefferson Station, New York

All animals have taste buds or an equivalent, and they are “tuned” to the nutrients the animals are specialized in. For example, cats can’t (and don’t need to) detect the presence of sugar, while primates surely can.

- Mike Maslanka, nutrition scientist, National Zoo

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