hopeful monster An individual which carries a macromutation that is of no benefit to that individual (i.e. the individual is a monster) but that may prove beneficial to one of its descendants if it undergoes further, but relatively minor, evolutionary change (i.e. the monster is hopeful). For example, the loss of the tail in descendants of Archaeopteryx was followed by the development of the tail feathers which stabilize the flight of modern birds (assuming there was a direct evolutionary line from Archaeopteryx to the birds). The hypothesis is advanced in order to explain the evolution of structures that appear to confer no benefit, or even disadvantages, until they reach their completed form. Many of the structures involved are explicable without invoking ‘hopeful monsters’ (e.g. partially evolved feathers may be useless for flight but provide thermal insulation; and an eye that works inefficiently may nevertheless be better than no eye at all). Macromutations that involve a major reorganization of the genes may effectively sterilize the animal and in any case an individual whose appearance is markedly different from that of other members of its species may have difficulty finding a mate. The hypothesis is now applied mainly to macromutations that affect regulatory genes (the genes that activate or de-activate genes which cause the synthesis of proteins); these may have major effects but involve no major, and probably sterilizing, genetic alteration.

hopeful monster An individual that carries a macromutation that is of no benefit to that individual (i.e. the individual is a monster) but which may prove beneficial to one of its descendants if it undergoes further, but relatively minor, evolutionary change (i.e. the monster is hopeful). For example, the loss of the tail in descendants of Archaeopteryx was followed by the development of the tail feathers which stabilize the flight of modern birds (assuming there was a direct evolutionary line from Archaeopteryx to the birds). The hypothesis is advanced in order to explain the evolution of structures that appear to confer no benefit, or even disadvantages, until they reach their completed form. Many of the structures involved are explicable without invoking ‘hopeful monsters’ (e.g. partially evolved feathers may be useless for flight but provide thermal insulation; and an eye that works inefficiently may nevertheless be better than no eye at all). Macromutations that involve a major reorganization of the genes may effectively sterilize the animal and in any case an individual whose appearance is markedly different from that of other members of its species may have difficulty finding a mate. The hypothesis is now applied mainly to macromutations that affect regulatory genes (the genes that activate or deactivate genes which cause the synthesis of proteins); these may have major effects but involve no major, and probably sterilizing, genetic alteration.

hopeful monster A hypothetical new phenotype, or monstrosity, that arises due to mutations that radically alter an individual's developmental pattern. Such an individual, it is claimed, could possess major innovations that equip it for an environment quite different from that of its immediate antecedents. The concept, which was introduced in 1933 by the geneticist R. Goldschmidt, presents a way in which, theoretically, a new group could arise in a single macroevolutionary leap, rather than by the gradual process of natural selection producing many small adaptive changes – the route favoured by orthodox neo-Darwinians. It is regarded by many as implausible and unsupported by fossil evidence.

hopeful monster in some theories of macroevolution, an organism displaying a radical mutation which nevertheless permits it to survive, produce offspring, and so potentially give rise to a new and distinct group of organisms.