Sobre la selección natural y la evolución

Cuál es la unidad evolucionaria más básica, el inviduo o el grupo?
Debate en torno a unas arañas de la especie Anelosimus studiosus
http://www.wired.com/2014/10/social-spider-group-evolution/
mi kaveza no puede pensar tanto
"A combination of group selection and individual selection could be the key to resolving this tension. Historically, researchers have thought of the two as extremes, always at odds, but “sometimes group selection and individual selection are not necessarily conflicting,” Nonacs said. Pruitt’s paper might help to promote this perspective, he said. In the case of the social spiders, “even though group and individual selection may be going in the same direction, group level is stronger,” Nonacs said."