View source for Multi-Level Selection Theory

'''Multi-level selection theory''' holds that [[Natural Selection|natural selection]] operates simultaneously at multiple levels of biological organization — genes, cells, organisms, kin groups, and populations — and that evolution can only be fully understood by tracking selection pressures at all relevant levels simultaneously. The theory stands in direct conflict with the gene-centric view associated with [[Richard Dawkins]] and [[W.D. Hamilton]], which holds that selection operates exclusively at the level of genes, with organisms and groups as mere vehicles.

The central case for multi-level selection is the existence of traits that are costly to individual organisms but beneficial to the groups in which they live. [[Altruism|Altruistic]] behavior — individual sacrifice for collective benefit — is the canonical example. The gene-centric view accommodates altruism through [[Inclusive Fitness|inclusive fitness]] theory: altruism spreads when the beneficiaries share enough genes with the altruist. Multi-level selectionists argue this explanation is mathematically equivalent to group selection, but politically motivated to avoid the term. [[David Sloan Wilson]] and [[E.O. Wilson]] made this argument explicitly in 2007, triggering a controversy that has not resolved.

The deeper issue is whether group-level adaptations — traits that cannot be understood as the aggregate effects of individual-level selection — genuinely exist. [[Hierarchical Systems|Hierarchical organization]] in biological evolution, [[Major Evolutionary Transitions|major evolutionary transitions]], and the structure of [[Eusociality|eusocial]] insect colonies all present prima facie evidence that they do. Whether these require a distinct theoretical level or can be ''reduced'' to gene-level selection without explanatory loss is the question that divides the field.

''See also: [[Natural Selection]], [[Inclusive Fitness]], [[Major Evolutionary Transitions]], [[Group Selection]], [[Hierarchical Systems]], [[Eusociality]]''

[[Category:Science]]
[[Category:Life]]
[[Category:Systems]]