{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"a9188ee60b4fa21f36fce67ed23faf4a8e1fe321a158fc2fda661eab84c23027","created":"2026-10-03T07:17:57Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"047bb6d528d3a3f8aac525cedb0090b6be2eeee79ae6cccec9f21eabbb9a2439","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"bio.fitness-landscapes.lewontin-paradox","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Simple theory says a species with a billion times more individuals should carry far more genetic variation, but diversity differs only about a hundredfold across animals whose numbers differ by more than ten orders of magnitude. What compresses diversity in large populations is unknown.","posed_since":"1974","precise":"Neutral theory gives nucleotide diversity $\\pi=4N_e\\mu$ ($N_e$ = effective population size, $\\mu$ = mutation rate per site per generation), yet across metazoans $\\pi$ varies over roughly two decades while census size $N_c$ varies over more than ten (Lewontin, 1974). Account quantitatively for the slope of $\\log \\pi$ versus $\\log N_c$ through linked selection (genetic draft from sweeps, as in traveling-wave theory, and background selection), population-size fluctuations, and mutation-rate scaling.","problem_ref":null,"references":"","settled_by":"A model with measured recombination maps, mutation rates and demographic histories across many species that reproduces the observed $\\pi$ versus $N_{c}$ relation.","status_note":"Buffalo (eLife 2021, doi 10.7554/eLife.67509) found that linked selection, even assumed strong and frequent, cannot explain the relation across 172 taxa; this remains disputed.","title":"Why genetic diversity barely grows with population size","topic_ref":"d9679f27d8e24851339481c38577825fa8afb7298403d565282e3b7505aed4ee"},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d503995b59b76879cde71fa4d6747c2493e8be2990dbad4ec4c59a51c58e97c3","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"f7f166a3e55f6da23d164aac5e75e6a12fce1fbcd7cf879f2565eaca9c5cae7a","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"8J6NrXM92GLOzHsFQx-nkLYZ8WSH2VFm7xyf2piYOrvvL1SRtkRyLHI3gVVzF-p0pI1AdOjb_uxiEmlP1GKOCA"},"schema":"pubphys.envelope/1"},"record_hash":"d503995b59b76879cde71fa4d6747c2493e8be2990dbad4ec4c59a51c58e97c3","leaf_index":767}