A Genetic Compatibility Framework: Resolving the Species Problem Through Empirical Offspring Production and Clonal Lineages

The species problem in biology persists due to the absence of a universal, empirically testable definition that applies across sexual, asexual, and borderline living organisms. We propose a novel, empirically grounded criterion that unifies species classification across all organisms. We define a genetic compatibility framework: a species is the largest group of organisms that are genetically compatible for reproduction (in sexual organisms, evidenced by the production of offspring irrespective of viability or fertility) or that form a shared clonal lineage with high genetic similarity (in asexual organisms). This empirical criterion unifies classification for bacteria, viruses, plants, and animals. Applications to plants, bears, whales, birds, canids, felids, and primates demonstrate consistent delineation of boundaries. Complete genomic sequencing reveals 12.5–27.3% of ape genomes fail to align one-to-one in comparisons, with human-ape gap divergence at approximately 12.5–27.3% plus 1.5–1.6% single-nucleotide variants, precluding offspring and confirming separate species.⁵ The framework resolves longstanding inconsistencies by prioritizing testable genetic outcomes over inferred processes.