Such expressions as that famous one of Linnæus, and which we often meet with in a more or less concealed form, that the characters do not make the genus, but that the genus gives the characters, seem to imply that something more is included in our classification, than mere resemblance. I believe that something more is included; and that propinquity of descent,—the only known cause of the similarity of organic beings,—is the bond, hidden as it is by various degrees of modification, which is partially revealed to us by our classifications (Darwin, 1859, p. 413f).

Wednesday 9 November 2011

Tweeted Histories I #Homology

@Goethe1824 I can relate a worm and a man via a third thing! I'll write a poem about it!
@sexy_Blumnbch What?
@henrich.B if you hang a human skeleton next to that of bird, you can compare their structures #Bronn1858
@Darwinathome's birdy
@sexy_Blumnbch Eww!
@MonsterMoa nah! what you want is a bauplan. #Owen1849
@Swiss_Pride What evidence have you got? You need space, time as well as form! #Agassiz1859
@Embryo.boy I think he means comparing embryos and how they develop #Gegenbaur1859
@Swiss_Pride no I don't!
@Darwinathome I found a birdy!
@MonsterMoa just compare the forearms of bats, humans and whales. See? Analogy!
@RayL Don’t just compare: find the origin of things. Homology? Bah! Homogeny!
@asagray I like @Darwinathome's birdy. Can u send photo?
@Stammbaum Origins, we need origins! My own Stammbaum gives origins; now all is homogeny
@Darwinathome can someone tell @Stammbaum to leave me alone?
@RayL Not all is homogeny, some comparisons are not true: homoplasy!
@Stammbaum Who cares. I have lots of stammbaume, one for every creature. All with homogeny, homoplasy and homology
@naefnotnaf @Stammbaum got it wrong. You can't mix phylogeny and systematics #Naef1919
@naefnotnaf homology is a systematic relationship separate from phylogeny
@angry_mayr Typologist!
@Zimmermann no it's not! homology is a transformational relationship.
@a.remane or a process #Remane1952
@willi Why not compromise? Use @naefnotnaf's systematics for taxa and @Zimmermann for their characters! #Hennig1950
@ggsimp what about ancestors? Homology is similarity between the bits of us and ancestors
@sokal_123 you mean overall similarity at a node? #SokalSneath63
@willi no, special similarity, that is synapomorphy #Hennig66
@angry_mayr Cladist!
@nelson_usa perhaps it's a non-transformational relationship? #NelsonPlat81
@beaty.boy Pattern Cladist!
@Colin82 non-transformational but based on similarity #Patterson82 
@ron.brady forget similarity, homology is simply an affinity. See @Goethe1824
@normlovesspiders homology is a three-item relationship regardless what is based on
@hennig_superstar %$#%! Homology is synapomorphy?
@k.nixon homology = synapomorphy + symplesiomorphy #NixonCarp11

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