Letters from the July 23, 2005, issue of Science News

Clearly a problem?

“Built for Blurs: Jellyfish have great eyes that can’t focus” (SN: 5/14/05, p. 307) states that “the resulting blurred view is good enough for spotting large objects such as mangrove roots.” It seems to me that the article is missing the crucial biological question presented by these eyes. My understanding is that the nervous system of a jellyfish contains no true nerves and no centralization. How can the simple neural net of a cnidarian interpret any image, blurry or not?

Rob Spivack
San Francisco, Calif.

Founding Fodder

The article “Founding Families: New World was settled by small tribe” (SN: 5/28/05, p. 339) features yet another study making summary statements on what is obviously inadequate sampling. Most of the language families from California to Alaska have not been represented in any DNA studies. Those of us who study cultures on the northwest coast of America see the enormous complexities of cultures in this area. Outdated and oversimplified terms such as “Amerind” simply do not make any sense.

Grant Keddie
Royal British Columbia Museum
Victoria, British Columbia

Double bubble

Maybe there was a belch of hydrogen sulfide involved in the Permian extinctions (“Last Gasp: Toxic gas could explain great extinction,” SN: 5/28/05, p. 339). However, did it leave some geological trace, as did the vast Siberian outpourings of magma, both on land and in the sea, over the course of a million years during the period?

Stan Skirvin
Scottsdale, Ariz.

The ocean venting proposed by Lee Kump’s group at Pennsylvania State University doesn’t refute that major volcanic eruptions contributed to the Permian extinction. The two phenomena could have combined their lethal effects. Some geologic evidence exists for ocean venting, such as fossil signs that hydrogen sulfide–producing bacteria lived unusually close to the surface in the Permian ocean. However, no direct evidence for high atmospheric concentrations of hydrogen sulfide gas has yet been found.—N. Moreira