Altruism
Wild strains of ''D. purpureum'' were taken from the Houston Arboretum to a lab where they were cultured in dishes. In each of 14 experiments, a pair of strains were placed in a dish in equal proportion, and one of the strains in each pair was labeled with a fluorescent dye. Food was withheld, causing the microbes in each dish to form dozens of slugs and fruiting bodies. Upon observing their social development, the team found that individual fruiting bodies contained predominantly one strain or the other. This shows that an individual ''D. purpureum'' isn't going to offer itself to form a stalk unless it's sure that the rest of the aggregate, benefit from its sacrifice or a close relative. This demonstrated that molecular recognition of "self" and "close to self" (the basis of a modern immune system) happens even in primitive organisms.References
Mycetozoa Dictyostelid species {{Amoebozoa-stub