Could a Robin and a Bluebird Have Babies? And More Questions From Our Readers

Could different backyard birds, such as a robin and a bluebird, produce viable offspring? Joseph Niemoeller | Glen Carbon, Illinois

Although closely related species can have offspring, they typically don’t. Robins and bluebirds may be able to hybridize (there are no documented cases), but they have different plumages, songs, foraging habits and nest types, so it would be unlikely for them to choose each other. Such differences, along with geographic range and habitat preferences, prevent species from interbreeding even when it’s possible. Some species, like mallard ducks, do hybridize frequently. But the hybrid young may be a “dead end,” since they may be less likely to survive to adulthood or find their own mates. Hybrid cases help scientists learn what traits are important in the evolution and maintenance of species. —Sarah Luttrell, researcher of birds and vertebrate zoology, National Museum of Natural History

Based on the 1968 film 2001: A Space Odyssey, the public seemed to think we’d soon travel to other planets. Why didn’t we? Johnson Alabama Kanell | Portland, Maine

When NASA started its Apollo program in the 1960s, the United States was in a space race with the Soviet Union. The government gave the program high priority—and a high budget to match. But the Apollo program was expensive, and political urgency disappeared after the moon landing. NASA’s human ambitions shifted toward collaborating on the International Space Station and building reusable space shuttles. At the same time, new advances allowed exploration of the moon and planets to continue without humans on board. Since 1970, seven rovers have landed on the moon, and six others (and a small helicopter) have explored Mars, while spacecraft like Cassini and Juno have probed the outer planets and their moons. Artemis 3, scheduled for 2026, plans to send humans to the moon for the first time since 1972. The goal, according to the mission’s website, is to “build a community on the moon, driving a new lunar economy and inspiring a new generation.” NASA hopes that a successful Artemis program will lead to human Mars missions in the 2030s. —Matthew Shindell, curator of planetary science and exploration, National Air and Space Museum

Did Native Americans have cats and dogs before the arrival of European colonizers? Joseph A. Leist | Hamilton, New Jersey

Domestic cats did not exist in the Americas before Europeans arrived. However, there was a diverse range of dogs. We think humans brought dogs from Eurasia at least 15,000 years ago. The dogs traveled with humans, who selectively bred them for many different purposes. For example, the Coast Salish Indigenous peoples of the Pacific Northwest bred a unique long-haired dog for their wool. They sheared or combed out hair from these “woolly” dogs, then spun it into yarn and wove it into intricate textiles for regalia, blankets and rugs. From the DNA sequenced from the only known woolly dog pelt (from 1859), currently in Smithsonian collections, we found that this woolly dog lineage is up to 5,000 years old. This dog has gene variants not seen in any other canid species. Many other dog species were kept by Indigenous groups for different reasons, including hunting and pulling sleds. The ancestors of today’s Arctic sled dogs came over from Siberia with Inuit people just 2,000 years ago. Most of the dog breeds Americans have today came much later, with European colonizers. —Audrey T. Lin, research associate in anthropology, National Museum of Natural History