Editing Blue whale (section)

===Evolution===
{{cladogram |align=right
|caption=<small>A [[phylogenetic tree]] of six baleen whale species<ref name=Arnason_etal_2018/></small>
|clades={{clade|style=font-size:75%;line-height:75%;width:350px;
|label1=[[Balaenopteridae]]
|1={{clade
   |1=[[Minke whale]]
   |2={{clade
      |1={{clade
         |1='''''B. musculus''''' ('''blue whale''')
         |2=''B. borealis'' ([[sei whale]])
       }}
      |2={{clade 
         |1=''Eschrichtius robustus'' ([[gray whale]])
         |2={{clade
            |1=''B. physalus'' ([[fin whale]])
            |2=''Megaptera novaeangliae'' ([[humpback whale]])
          }}
       }}
    }}
 }}
}}
}}
Blue whales are [[rorquals]] in the family [[Balaenopteridae]]. A 2018 analysis estimates that the Balaenopteridae family diverged from other families in between 10.48 and 4.98&nbsp;million years ago during the late [[Miocene]].<ref name=Arnason_etal_2018>{{cite journal | author1=Árnason, U. | author2=Lammers, F. | author3=Kumar, V. | author4=Nilsson, M. A. | author5=Janke, A. | title=Whole-genome sequencing of the blue whale and other rorquals finds signatures for introgressive gene flow | journal=[[Science Advances]] | volume=4 | issue = 4 | pages=eaap9873 | date=2018| bibcode=2018SciA....4.9873A | doi=10.1126/sciadv.aap9873 | pmid=29632892 | pmc=5884691}}</ref> The earliest discovered anatomically modern blue whale is a partial skull fossil from southern [[Italy]] identified as ''B.'' cf. ''musculus'', dating to the Early [[Pleistocene]], roughly 1.5–1.25&nbsp;million years ago.<ref name=Bianucci_etal_2019>{{cite journal | author1=Bianucci, G. | author2=Marx, F. G. | author3=Collareta, A. | author4=Di Stefano, A. | author5=Landini, W. | author6=Morigi, C. | author7=Varola, A. | title=Rise of the titans: baleen whales became giants earlier than thought | journal=[[Biology Letters]] | volume=15 | issue = 5 | page=20190175 | date=2019| doi=10.1098/rsbl.2019.0175 | pmid=31039728 | pmc=6548731}}</ref> The Australian [[pygmy blue whale]] diverged during the [[Last Glacial Maximum]]. Their more recent divergence has resulted in the subspecies having a relatively low genetic diversity,<ref name=Attard_etal_2015>{{cite journal | author1=Attard, C. R. M. | author2=Beheregaray, L. B. | author3=Jenner, K. C. S. | author4=Gill, P. C. | author5=Jenner, M.-N. M. | author6=Morrice, M. G. | author7=Teske, P. R. | author8=Moller, L. M. | title=Low genetic diversity in pygmy blue whales is due to climate-induced diversification rather than anthropogenic impacts | journal=Biology Letters | volume=11 | issue=5 | page=20141037 | date=2015| doi=10.1098/rsbl.2014.1037 | pmid=25948571 | pmc=4455730}}</ref> and New Zealand blue whales have an even lower genetic diversity.<ref name=Barlow_etal_2018>{{cite journal | author1=Barlow, D. R. | author2=Torres, L. G. | author3=Hodge, K. B. | author4=Steel, D. | author5=Baker, C. S. | author6=Chandler, T. E. | author7=Bott, N. | author8=Constantine, R. | author9=Double, M. C. | author10=Gill, P. | author11=Glasgow, D. | author12=Hamner, R. M. | author13=Lilley, C. | author14=Ogle, M. | author15=Olson, P. A. | title=Documentation of a New Zealand blue whale population based on multiple lines of evidence | journal=Endangered Species Research | volume=36 | pages=27–40 | date=2018| doi=10.3354/esr00891 | doi-access=free}}</ref>

[[Whole genome sequencing]] suggests that blue whales are most closely related to [[sei whale]]s with gray whales as a [[sister group]]. This study also found significant [[gene flow]] between minke whales and the ancestors of the blue and sei whale. Blue whales also displayed high genetic diversity.<ref name=Arnason_etal_2018/>

====Hybridization====
Blue whales are known to [[interbreed]] with [[fin whale]]s.<ref>This may have already been known to Icelanders in the 17th century, see {{cite book |last=Lindquist |first=Ole |date=1997 |title=Peasant fisherman whaling in the Northeast Atlantic area, ca 900-1900 AD |url=https://www.fishernet.is/images/stories/peasant_fisherman_whaling.pdf |location=Akureyri |publisher=Háskólinn á Akureyri |page=27 |isbn=9979-834-10-2 |access-date=2025-04-16}}</ref> The earliest description of a possible hybrid between a blue whale and a fin whale was a {{cvt|20|m}} anomalous female whale with the features of both the blue and the fin whales taken in the North Pacific.<ref name=Doroshenko_1970>{{cite journal | author1=Doroshenko, V. N. | title=A whale with features of the fin and the blue whale | journal=Izvestia TINRO | volume=70 | pages=255–257 | date=1970}}</ref> A whale captured off northwestern Spain in 1984, was found to have been the product of a blue whale mother and a fin whale father.<ref name=Berube_Aguilar_1998>{{cite journal | author1=Bérubé, M. | author2=Aguilar, A. | title=A new hybrid between a blue whale, ''Balaenoptera Musculus'', and a fin whale, "B. Physalus:" frequency and implications of hybridization | journal=Marine Mammal Science | volume=14 | issue=1 | pages=82–98 | date=1998| doi=10.1111/j.1748-7692.1998.tb00692.x| bibcode=1998MMamS..14...82B }}</ref>

Two live blue-fin whale [[Hybrid (biology)|hybrids]] have since been documented in the Gulf of St. Lawrence (Canada), and in the Azores (Portugal).<ref name=Berube_etal_2017>{{cite conference | author1=Berube, M. | author2=Oosting, T. | author3=Aguilar, A. | author4=Berrow, S. | author5=Hao, W. | author6=Heide-Jørgensen, M. P. | author7=Kovacs, K. M. | author8=Landry, S. | author9=Lydersen, C. | author10=Martin, V. | author11=Øien, N. | author12=Panigada, S. | author13=Prieto, R. | author14=Ramp, C. | author15=Robbins, J. | title=Are the "Bastards" coming back? Molecular identification of live blue and fin whale hybrids in the North Atlantic ocean | conference=22nd Biennial Conference on the Biology of Marine Mammals | location=Halifax, Nova Scotia, Canada | date=2017}}</ref> DNA tests done in Iceland on a blue whale killed in July 2018 by the Icelandic whaling company [[Hvalur hf.]], found that the whale was the offspring of a male fin whale and female blue whale;<ref>{{cite web |last=Kilvert|first=Nick|url=https://www.abc.net.au/news/science/2018-07-20/dna-shows-blue-whale-hybrid-iceland-institute-says/10017276 | title=DNA test shows slaughtered blue whale is a hybrid, Iceland marine institute says | date=20 July 2018 | publisher=[[Australian Broadcasting Corporation|ABC]] | access-date=21 December 2019}}</ref> however, the results are pending independent testing and verification of the samples. Because the International Whaling Commission classified blue whales as a "Protection Stock", trading their meat is illegal, and the kill is an infraction that must be reported.<ref>{{cite web |last=Fishman|first=Margie|url=https://awionline.org/press-releases/hybrid-blue-fin-whale-still-protected | title=Hybrid blue-fin whale is still protected | date=19 July 2018 | publisher=[[Animal Welfare Institute]] | access-date=21 December 2019}}</ref> Blue-fin hybrids have been detected from genetic analysis of whale meat samples taken from Japanese markets.<ref name=Palumbi_Cipriano_1998>{{cite journal | author1=Palumbi, S. R. | author2=Cipriano, F. | title=Species identification using genetic tools: the value of nuclear and mitochondrial gene sequences in whale conservation | journal=Journal of Heredity | volume=89 | issue=5 | pages=459–464 | date=1998| doi=10.1093/jhered/89.5.459 | pmid=9768497 | doi-access=free}}</ref> Blue-fin whale hybrids are capable of being fertile. Molecular tests on a {{cvt|70|ft|order=flip}} pregnant female whale caught off Iceland in 1986 found that it had a blue whale mother and a fin whale father, while its fetus was sired by a blue whale.<ref name=Spilliaert_etal_1991>{{cite journal | author1=Spilliaert, R. | author2=Vikingsson, G. | author3=Arnason, U. | author4=Palsdottir, A. | author5=Sigurjonsson, J. | author6=Arnason, A. | title=Species hybridization between a female blue whale (''Balaenoptera rnusctllus'') and a male fin whale ("B.pbysalus"): Molecular and morphological documentation | journal=[[Journal of Heredity]] | volume=82 | issue=4 | pages=269–274 | date=1991| doi=10.1093/oxfordjournals.jhered.a111085 | pmid=1679066}}</ref>

In 2024, a genome analysis of North Atlantic blue whales found evidence that approximately 3.5% of the blue whales' genome was derived from hybridization with fin whales. Gene flow was found to be unidirectional from fin whales to blue whales. Comparison with Antarctic blue whales showed that this hybridization began after the separation of the northern and southern populations. Despite their smaller size, fin whales have similar cruising and sprinting speeds to blue whales, which would allow fin males to complete courtship chases with blue females.<ref name=Jossey_et_al_2024>{{cite journal | author1=Jossey, Sushma | author2=Haddrath, O. | author3=Loureiro, L. | author4=Weir, J. | author5=Lim, B. | author6=Miller, J. | author7=Scherer, S. | author8=Goskøyr, A | author9=Lille-Langøy, R | author10=Kovacs, Kit | author11=Lyndersen, C | author12=Routti, H | author13=Engstrom, M | title=Population structure and history of North Atlantic Blue whales (''Balaenoptera musculus musculus'') inferred from whole genome sequence analysis | journal=[[Conservation Genetics]] | volume=Open access | date=6 January 2024 | issue=2 | pages=357–371 | doi=10.1007/s10592-023-01584-5| doi-access=free | bibcode=2024ConG...25..357J | hdl=11250/3164708 | hdl-access=free }}</ref>

There is a reference to a humpback–blue whale hybrid in the [[South Pacific Ocean|South Pacific]], attributed to marine biologist Michael Poole.<ref name=Reeves_etal_2002/><ref name=Hatch_etal_2006>{{cite journal | author1=Hatch, L. T. | author2=Dopman, E. B. | author3=Harrison, R. G. | title=Phylogenetic relationships among the baleen whales based on maternally and paternally inherited characters | journal=[[Molecular Phylogenetics and Evolution]] | volume=41 | issue=1 | pages=12–27 | date=2006| doi=10.1016/j.ympev.2006.05.023 | pmid=16843014| bibcode=2006MolPE..41...12H }}</ref><ref>{{cite web |title=Genomic analyses reveal an absence of contemporary introgressive admixture between fin whales and blue whales, despite known hybrids|url=https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0222004|date=25 September 2019|access-date=15 February 2025}}</ref>