Which Animal is the Smartest, How Did Fingernails Evolve and More Questions From Our Readers

Which animals have the highest I.Q., and how is it measured?
Rob Loughridge
Honolulu, Hawaii

Measuring I.Q. is difficult, even in humans. But my friend Diana Reiss, a psychologist and author of the book The Dolphin in the Mirror, notes that I.Q. generally translates into intelligence, and that intelligence is, in the words of the cybernetician Ross Ashby, “the power of appropriate selection,” whether in animals (including people) or machines. By that standard, studies have shown that great apes, dolphins, elephants and crows demonstrate problem-solving skills that could be considered a sign of higher intelligence.
Donald E. Moore III
associate director for animal-care sciences, National Zoo

What was “clockwise” called before there were clocks?
Richard L. Bode
Vancouver, Washington

Clock dials and clock-hand rotation were standardized in Western Europe by the end of the 17th century, but “clockwise” (rotating to the right) and “counterclockwise” didn’t appear until about 200 years later, according to the Oxford English Dictionary. Before there were clocks, there were sundials, and “sunways,” later “sunwise,” referred to the apparent daily movement of the sun. In the Northern Hemisphere, that is east to west, and the shadows on sundials rotate to the right.
Carlene Stephens
curator of time collections, American History Museum

How do scientists know how much space material is falling to Earth?
Ralph C. Zeien
Scottsdale, Arizona

The United States Space Surveillance Network uses optical telescopes, radio frequency, radar and other remote sensors to monitor manufactured material (or “space junk”) in Earth orbit. The National Oceanic and Atmospheric Administration monitors natural material using a variety of remote-sensing techniques. Both types of material sometimes fall toward the Earth, but they typically burn up in the atmosphere or land in the oceans.
Valerie Neal
curator of space history, National Air and Space Museum

How did fingernails evolve?
Jeremy Chalchinsky
New York

The earliest known fingernails are thought to have occurred in Teilhardina brandti, a lemur-like primate from the Eocene, long before the earliest known hominin. Fingernails are believed to have made it easier to grasp small-diameter branches and food.
John Gurche
paleo-artist, Natural History Museum, and author of Shaping Humanity: How Science, Art, and Imagination Help Us Understand Our Origins

How much exhibition space does the Smithsonian have, and how much
storage space?
Roger Nelson
Ringgold, Georgia

The Smithsonian exhibits about two million objects in about 1.1 million square feet in its museums. (In addition, two million objects are on loan across the United States.) About 130 million items are studied and conserved in 2.2 million square feet of storage space.
Richard Kurin
under secretary for history, art and culture