The primitive form of crayfish anxiety probably shares some evolutionary origins with the more developed human form, although the ways in which this emotion has shaped each species remain unknown.

Toxicologists have long held that the dose makes the poison: A substance can cause harm only in amounts high enough to overwhelm the body’s defenses. But a major conceptual shift is underway, a leading expert said recently at AAAS, with much more attention being paid to low-dose chemical exposures and the impact they can have even many years later.