The concept of superorganism is under dispute, as many biologists maintain that in order for a social unit to be considered an organism by itself, the individuals should be in permanent physical connection to each other, and its evolution should be governed by selection to the whole society instead of individuals. While it's generally accepted that the society of eusocial animals is an unit of natural selection to at least some extent, most evolutionists claim that the individuals are still the primary units of selection.