Researchers who study the fossil record are seeking to determine whether the impact made by a comet or meteor really did decimate up to half of the life on this planet at the end of the Cretaceous period. Questions whether the extinction of plant and animal life was abrupt, started before the impact, or was a gradual change. (KR)

The hazards posed by new techniques of genetic manipulation have prompted scientists to regulate and in some cases restrict their own basic investigations. Describes some possible applications of the new techniques and outlines the established research guidelines. (GS)

Discusses various theories about life on Mars and biochemical experiments pertaining to the origin of life. (MLH)

Relates occurrences at the Asilomar conference that led to the drafting of guidelines for gene-transplant research. The guidelines allow some experiments, defer others until safer containment is available, and ban those considered highly dangerous. (GS)

Presents arguments against the recent "punctuated equilibrium" point of view expressed by evolutionists Stephen Jay Gould and Niles Eldredge. Reviews evidence for continuous and gradual change, as recently cited by four anthropologists in the July 9 issue of "Nature." (CS)