The eyes have it
Just finished the latest issue of your spectacular magazine. I’ve been a reader for many years, but this is the first time I’ve felt compelled to write in. In the article about the tadpole (“Tiny voltage grows eyes in strange places,” SN: 12/31/11, p. 5), the final sentence is a quote from Coffman: “The fact that a narrow range of voltage is enough to specify an eye is kind of amazing.”

What might be even more amazing is if researchers find out the voltage level that prompts cells to initiate and grow malignant tumors. I hope someone will help me stir up some interest in this research idea.
Bob Wyrick, Portland, Ore.

Dreaming clearly
Laura Sanders’ article “First brain image of a dream made” (SN: 12/17/11, p. 10) is most interesting; however, the definition of lucid dreaming is incomplete. Sanders writes, “Lucid dreaming is the rare ability to direct behaviors while in a deep sleep.” Actually, lucid dreaming is defined as knowing we are dreaming while we are dreaming. After that epiphany occurs, some people can direct or control their dream behaviors but others cannot. Indeed, different factions differ as to the desirability of attempting lucid dream control. Perhaps this research will throw new light on this issue.
Margaret Jane Kephart, Boulder, Colo.

Computing ‘junk’ DNA
The conclusion that “junk DNA” is not trash (“Missing lincs,” SN: 12/17/11, p. 22; “Turns out that ‘junk DNA’ wasn’t just talking trash,” SN: 12/17/11, p. 2) should have been obvious to computer programmers from the beginning. I have been using the following analogy ever since the junk DNA term entered the public literature: DNA strands are much like computer programs, which at the machine language level typically consist of long strings of “bytes,” each consisting of eight “bits.” Any given byte may be part of a computer instruction, part of a binary number or the encoding of an alphanumeric character (such as integers, punctuation marks or other characters).

If you try to read a program as if it were all alphanumeric characters, the result would be mostly gibberish. This “gibberish” is the programming that tells the computer hardware how to perform what it is intended to accomplish.

Very much like in DNA, some parts of the program are executed only once (at startup) and then turned off but not discarded. They may be turned on again if the program is “rebooted,” very much like parts of the DNA in a new embryonic cell.

You see, programming was around long before the stored-program computer was invented by John von Neumann in 1945. (Sorry, John.)
Richard A. Brouse, Orland, Calif.

Counting trees for climate
The article “Columbus’ arrival linked to CO2 drop” (SN: 11/5/11, p. 12) theorizes that because the population was decimated by European diseases, the open ground that people would have created by burning for farming gradually filled in with trees. These additional trees absorbed great amounts of carbon dioxide, resulting in the Little Ice Age in Europe. If this theory holds true, then conversely the mass cutting down of trees in the last century would result in the Earth’s surfaces becoming warmer. Has this been considered?
Jack Sarver, Pinckney, Mich.

Deforestation is considered to be an important contributor to climate change. In the 1990s, the mass clearing of trees in the tropics released about 1.5 billion metric tons of carbon into the atmosphere every year — about one-fifth of all greenhouse gas emissions caused by human beings. — Devin Powell

From the Nature Index

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