The following five sentences, labeled 1 to 5, relate to a single topic. Four of these sentences can be arranged to form a logical paragraph. Identify the sentence that does not fit with the others and enter its number as your answer.

1. Altruistic behaviors, despite their apparent contradiction to individual survival instincts, are central to understanding complex social structures through an evolutionary lens.
2. The theory of kin selection elucidates how self-sacrificial acts towards genetic relatives can enhance the propagation of shared genes, thus contributing to an organism's inclusive fitness.
3. Critics contend that an overreliance on genetic determinism within evolutionary explanations for altruism neglects the profound influence of cultural norms, social learning, and conscious ethical frameworks.
4. Beyond familial ties, reciprocal altruism accounts for cooperative exchanges among unrelated individuals, where the expectation of future repayment underpins seemingly selfless actions.
5. Therefore, what appears as unconditional selflessness often functions as an adaptive strategy, promoting gene survival either directly through shared lineage or indirectly through mutually beneficial interactions.