Leaving sea life high and dry?
I wonder whether the activity of corticotropin-releasing hormone (CRH) triggered just before the onset of labor in mammals and its importance in the metamorphosis of amphibians when water levels drop could be triggered by some mechanism that measures external pressure ("Mammal birth signal cues tadpole to morph," SN: 5/10/97, p. 286). After all, in both processes, the animal must adapt to living in an environment of low water pressure after having been in aquatic surroundings.
I wonder, too, what role CRH may have played in evolution. Rather than asking what caused life to wander out of the seas and onto dry land, perhaps we should assume that the water went away and life was forced to adapt to living on dry land. Organisms that developed CRH could survive more easily. Perhaps we shouldnıt be looking at lung fish as the intermediate species, but rather at frogs and other amphibians -- particularly those that metamorphose.
"Pressure changes are certainly a possibility for the environmental cue," says Robert Denver of the University of Michigan in Ann Arbor.
-- C. Mlot
Dating the dog
I worry about the methods used to infer a domestication date of 100,000 or more years ago for dogs ("Stalking the Ancient Dog," SN: 6/28/97, p. 400). The phylogenetic methods used to obtain this date disregard the action of selection and isolation by the hand of man. Such forces are likely to change drastically the rate of nuclear as well as mitochondrial DNA substitution, destroying both the regularity of the molecular clock used and confidence in the date.
Litigation slows cleanup
Regarding the news brief "Superfund sites and birth defects" (SN: 6/21/97, p. 391), is not one of the reasons it has taken so long for the evaluation and cleanup of Superfund sites the large amount of litigation associated with the process? In fact, has not the Superfund been referred to as the Lawyers Guaranteed Employment Act because of the significant amount of the fund that has gone to attorneys?
Luis L. Villarruel
Legal costs associated with the Superfund sites are indeed substantial. A December 1995 report by the Cato Institute said the federal government spends up to $300 million a year on "lawyering and negotiating," while private parties spend three times as much. Indeed, it notes, "trade gossip reports instances of legal bills that are three or four times the cost of a potentially responsible partyıs share of a cleanup."
-- J. Raloff
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