We have never been individuals

Subtitle of an article by Gilbert et al. entitled "A symbiotic view of life," The Quarterly Review of Biology, Vol. 87, No. 4 (December 2012), pp. 325-341. The following is an excerpt of the section on evolutionary individuality beginning on p. 331:

"From the above discussion, it is evident that organisms are anatomically, physiologically, developmentally, genetically, and immunologically multi-genomic and multispecies complexes. Can it be that organisms are selected as multigenomic associations? Is the fittest in life’s struggle the multispecies group, and not an individual of a single species in that group?"

"An instructive example comes from studies of the pea aphid, Acyrthosiphon pisum and the several species of bacteria that live in its cells. [...] This symbiotic relationship appears to fulfill the criteria for group selection: alleles can spread throughout a population because of the benefits they bestow on groups, irrespective of the alleles’ effect on the fitness of individuals within that group. Except, in this case, the beneficial alleles are genetic variations in bacterial symbionts, which provide their hosts with a second source of inherited selectable variation.

"We are not genetic or anatomical individuals; and if there is no 'individual organism,' what remains of classic notions of 'individual selection?' This moves the biological discussion of symbiotic associations into the venerable conception of 'group selection,' so abhorrent to neo-Darwinian sensibilities, and so denigrated by sociobiologists’ conceptions based on game theory."