How Did Right-Handedness Evolve? And More Questions From Our Readers

You asked, we answered

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Illustration by Scott Bakal

How far back does right-handedness go in our evolutionary history?
Patrick Emmett
Bethesda, Maryland

It goes way back—hundreds of thousands of years. Early stone tools indicate a right-hand preference, and so does paleolithic art. Most prehistoric handprints are of the right hand, while painted hand silhouettes are usually of the left, suggesting they were drawn with the right. Today, about 90 percent of humans are right-handed. A lesser pattern of right-hand dominance has been observed in some other living primate populations, too, such as chimpanzees.
Briana Pobiner
paleo-anthropologist, Human Origins Program, National Museum of Natural History

Black holes: spheres or disks?
John Mulkeen
West Yarmouth, Massachusetts

Black holes are spheres. But a black hole is generally surrounded by a disk of hot, bright in-falling material. That material is known as an “accretion disk.”
Belinda Wilkes
director, Chandra X-ray Center, Harvard-Smithsonian Center for Astrophysics

Why are some lakes designated by “lake” first (e.g., Lake Superior) and others the opposite (e.g., Upper Straits Lake)?
Gary Dembs
Huntington Woods, Michigan

It seems to depend on who named the lake—or other geographical feature, for that matter—in question. French and Spanish explorers put the noun first and then the adjective; English-speaking explorers put the adjective first. Lake Superior was originally “Lac Supérieur” (or what an English speaker might have called “Upper Lake”). But beware; this pattern is by no means consistent. A number of recent man-made lakes have been christened in the French or Spanish manner—Lake Cumberland in Kentucky is one example that comes to mind. To some ears, that simply sounds more impressive.
Doug Herman
geographer, National Museum of the American Indian

Where do urban birds go when they die? We have lots of pigeons, sparrows and other birds where I live, but I’ve never seen a dead one on the street.
Edna Gross
Brooklyn, New York

That’s because dead city birds are quickly consumed by rats and feral cats. Even in the city, it’s a jungle out there.
Gary Graves
curator of birds, National Museum of Natural History

Is the amount of water on earth finite?
Wayne Rhodes
Deerfield, Illinois

Yes, it is. The water that cycles among the earth’s oceans, atmosphere and land surface can be viewed as a closed system. That means that the total amount of water doesn’t change. How this water originated is the subject of research. Water can be released by volcanic activity (quite a bit of which occurred as the early earth cooled), or it could have been added to the early earth from impacting objects, such as comets.
Andrew Johnston
geographer, Center for Earth and Planetary Studies, National Air and Space Museum