Why Do Humans Have Canine Teeth and More Questions From Our Readers
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Why do humans have canine teeth?
Patrick McGannon, Surprise, Arizona
All primate species have them, says Sabrina Sholts, a curator of physical anthropology at the Museum of Natural History. Early hominids may have found those four sharp teeth at the corners of the jaws a handy weapon for taking prey, preventing others from taking them prey and competing for mates. Over millions of years, possibly in response to dietary changes, the teeth became smaller. We modern humans use them to bite food and open cellophane-wrapped packages.
I’ve read both that modern humans interbred with Neanderthals and that they didn’t. Which is it?
Robert Redinger, Grant, Michigan
There is evidence that they did, in a limited way, says Richard Potts, director of the Human Origins Program at the Museum of Natural History. Neanderthal DNA makes up a small percentage of the DNA in non-African people today, suggesting that people who migrated beyond Africa 50,000 to 60,000 years ago interbred with Neanderthals, despite their differing bodies. People received Neanderthal genes related to some important functions, including blood clotting, but for unknown reasons, the two seem to have stopped interbreeding after that. Most researchers consider the Neanderthals, who went extinct about 40,000 years ago, a separate species.
Are bees attracted to flowers by color or scent?
Patricia L. Orr, Carolina, Puerto Rico
Color and scent—and more. David Roubik, an entomologist at the Smithsonian Tropical Research Institute, notes that bees are 100 times more sensitive to odor than humans are. In addition, the insects’ attraction to color includes ultraviolet light, which humans can’t see. Plus recent research has found that electricity also plays a role. Flowers have a slightly negative charge relative to the ambient air; bees get a positive charge from flying. The bees seem to sense the difference, which helps pollen stick to their bodies.
Did the Smithsonian Institution ever call on Theodore Roosevelt to identify a mammal specimen?
Bruce Ralston, Temecula, California
The 26th president was a recognized expert on large mammals in North America, and he had a long relationship with the Smithsonian. (Among other things, he led a yearlong Smithsonian expedition to Africa to collect specimens in 1909.) But Darrin Lunde, collections manager at the Museum of Natural History, says there is no evidence that the Institution called on him for taxonomic help.
Why does Earth have only one moon when other planets have more than one?
Kenneth Haines, Taylor, Michigan
Planets acquire moons in different ways. Mars, for example, captured its two moons when they wandered within its gravitational pull, says David DeVorkin, curator of space at the Air and Space Museum. Other planets and moons may have “co-formed,” or settled out of the celestial dust at the same time. Our moon apparently formed out of debris left from a collision about 4.5 billion years ago between Earth and a mass of rock roughly the size of Mars.
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