A recent study on fish from areas of high and low predation is challenging evolutionary theories of senescence, the rate at which animals degenerate with age. "We instead found that senescence was a mosaic of traits. ... The composite picture is that all of these fish deteriorate with age, but the comparative rates of deterioration is a mix of responses, most of which do not correspond to classical theory." As is usually the case, an aspect of biology is proving to be more complex than first imagined. "The differences between these results and the classical predictions gives cause to take the new, more derived, theories for the evolution of the aging process more seriously."