Consider numbers
I have been a faithful subscriber to Science News for a long time, since I subscribed for my kids in the 1960s. I don’t have a degree but was a naval aviator for 32 years. I just cannot get used to converting kilometers per hour to miles per hour each time I encounter astronomical rates of speed in your articles. My flight career in the U.S. Navy began from helicopters, through patrol planes, then F-4B Phantom jets. Everything was in knots, nautical miles and Mach number. During combat tours in Vietnam we got used to kilometers, but miles and miles per hour never left us. Your use of kilometers per hour causes me to stop and convert.
Joe R. Brewer, Pensacola, Fla.

Please excuse me for being pedantic, but ponder what information is conveyed by “observed lithium levels are three or four times lower than Big Bang physics predicts” “Lithium mystery could get deeper,” (SN: 9/8/12, p. 14). One time lower means zero. Three or four times lower mean negative quantities of lithium, which are nonsense. Fractions are best conveyed by terms indicating division, such as one-third. If all else fails, percent of works. Please join this old crank in efforts to run goofy number rendition out of fashion.
Brent G. Boving, Northville, Mich.

The reader is correct. Former Editor in Chief Tom Siegfried was known to stomp into a writer’s or editor’s office and demand a mathematical explanation (which of course could not be produced) upon catching a “times lower than” error. We regret letting one slip through. —Eds.

Peaceful prehistory
In “Mideast violence goes way back” (SN: 8/25/12, p. 16), archaeologist Augusta McMahon is quoted as saying “Prehistory was not peaceful.” When looking back only 6,000 years she is clearly correct, but human history goes back a bit more than that. My reading is that human history prior to 14,000 years or so was quite peaceful. The question is what happened to make us so aggressive, competitive and violent?
Jim Tierney, Auburn, Maine

There’s little evidence regarding ancient rates of violence one way or the other. New research on modern hunter-gatherers in Papua New Guinea suggests that historically, violence decreased with the transition from small-scale groups to state societies “In New Guinea, peace comes with a price,” ( SN Online 9/27/12 ). —Bruce Bower