coevolution ...

anchoring must necessarily occur in any physically embedded system that comprises a symbolic reasoning component.

environments simply are not fixed places that living things must fit into, adapt to, but the busy activity of living things themselves, working out their ways of life together as parts of the live earth. coevolution in eco-systems now seems a matter of creatures changing themselves from the inside, in response to their environment, and prodding changes in other creatures that are part of their environment. a change in one species will thus be reflected by changes in some others. each species is continually incorporating raw materials into its bodies, and being transformed in turn into raw materials for others.

coevolution happens when two or more species reciprocally influence each other's evolution. it is most often invoked to explain coadaptations and dependence between species. parasites and hosts, is an example of antagonistic coevolution, which can lead to evolutionary 'arms races'.

insects and plants influence each other's evolution, by the evolution of insecticides in plants and of detoxification and avoidance mechanisms in insects. evolutionary relations between insects and plants less often take the form of coevolution than of sequential evolution, in which plant evolution influences insect evolution but not vice versa.

the level of virulence of parasites can evolutionarily decrease or increase. two factors that influence it are kin selection and the mode of transmission of the parasite between hosts.

coevolutionary “arms races” between predators and prey may often show an evolutionary pattern called escalation. we must distinguish escalation from evolutionary progress. if evolution is progressive, organisms will become better adapted to their surroundings through evolutionary time, if it is escalatory, the improvement in predatory adaptations may be matched by improvements in prey defences/deteriotion, and neither ends up any better off.

it is indeed in the long-term interest of a parasite species not to destroy the resource it lives off. rates of change, and relative competitive abilities, need not be constant.

the main point is that any old interaction, symbiosis, mutualism, etc. is not synonymous with coevolution.