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

Sunday, 6 November 2011

The Autonomous Algorithm: Malpractice in Theory

In our last post we introduced the topic of the Autonomous Algorithm, a black box that acts as the foundation for a theory and method. In this post we explain what we mean by theory and method and why we believe that no tool can function as a logical foundation. Doing so is a form of malpractice.

For all the non-philosophers reading this post, we define theory as a set of mathematical principles on which an activity is based. The set of principles that underlie the study of geophysics is that radio waves and sound waves for instance have different levels of penetration. When a sound wave is reflected it can tell us the density and depth of an object, like a rock. These principles are based on physics, and not on the actual program that models the depth and density of rock. Doing that would be putting the cart before the horse. If we change the way we model the results of our acoustic test, we do not change the underlying principles of physics.

A method is a procedure to accomplish something. Methods are generally activities that can be done by pen and paper (although sometimes they are easier when automated) in which we determine the steps, for instance, to find out how to tell what is beneath a particular surface. The implementation is the tool that is used to do implement the method. This is usually as a computer algorithm. So, an algorithm is a tool that is based on a method that is underpinned by a theory. Seems simple enough, but this is often misinterpreted.