BioConcepts

affinityaffinitas (lat.); Affinität (ger.)

• Resemblance in structure, properties, or composition between different animals, plants, or mineral substances; similarity of nature or kind; (as a count noun) a point of resemblance; (occasionally) †a form which resembles or is related to another (obsolete). In later use also: (Biology) such resemblance taken to imply differentiation from a common ancestral type; genetic relationship as deduced from such resemblance. (OED 2012)
  category homology

  1593

  Quemadmodum et in forma cum Absynthio tanta est Santonici affinitas, quæ multis etiam eruditis imposuit, nisi qualitatibus ipsis indicarentur. […] Absynthii cum Santonico in figura affinitas, ut eorum discrimen à loco natali præcipuè dependere videatur, ne qualitatum differentias attingamus.

  Bauhin, J. (1593). De plantis absynthii nomen habentibus caput desumptum: 5; 140.
  

  1751

  Methodi Naturalis Fragmenta studiose inquirenda sunt.
  Primum & ultimum hoc in Botanicis desideratum est.
  Natura non facit saltus.
  Plantae omnes utrinque affinitatem monstrant, uti Territorium in Mappa geographica.

  Linné, C. (1751). Philosophia botanica: 27 (No. 77).

  1774

  In this groupe we find an extensive tribe of native birds, with their varieties and affinities

  Goldsmith, O. (1774). History of the Earth, vol. 6: 22.
  

  1777

  Naturalium corporum continuum nexum esse, ut jugi serie se singulae excipiant, neque ab uno ad alterum saltum facere naturam antiquitus dictum est. Retractatum hodie a multis argumentum dudum placuit, & quum quod alii quoque animadverterunt, videremus spargi in retis speciem lateralibus nexibus mire implicitis rerum affinitates, eas tabula aliqua exprimere abhinc multis annis tentavimus […]. Ceterum quum probe sciamus alios in instruenda naturae scala magis sectari formarum similitudinem, alios structuram, alios plus tribuere organorum multitudini &C perfectioni, alios elementum quod animalia habitant, motus, propagationis aliarumque qualitatum convenientiam respicere, alios sibi in numeris placere, alios magis animae facultates urgere; ut omnibus placeremus, modo ab hac modo ab alia parte affinitates nostras deduximus, ita tamem, ut quantum fieri posset, conjunctssima semper, quae pluribus inter se characteribus convenirent, sibi maxime fierent propinqua. Nam si ab una tantum qualitate proficiscaris, alio atque alio modo dispone genera debebunt.

  Hermann, J. (1777). Affinitatum animalium tabulam brevi commentario illustratam: 3-4; 6.
  

  1781

  Die Vernunft bereitet […] dem Verstande sein Feld 1. durch ein Princip der Gleichartigkeit des Mannigfaltigen unter höheren Gattungen, 2. durch einen Grundsatz der Varietät des Gleichartigen unter niederen Arten; und um die systematische Einheit zu vollenden, fügt sie 3. noch ein Gesetz der Affinität aller Begriffe hinzu, welches einen continuirlichen Uebergang von einer ieden Art zu ieder anderen durch stufenartiges Wachsthum der Verschiedenheit gebietet.

  Kant, I. (1781). Critik der einen Vernunft: 657-8.
  

  1786

  Verschwägerung (Affinität). […] Affinität. Verschwägerung ist der Nexus, worin der eine Ehegatte mit den Blutsfreunden des andern stehet. Nach einem willkührlichen Begrif kann man freilich die Affinität noch weiter hinaus erstreken.

  Tittel, G.A. (1786). Erlauterungen der theoretischen und praktischen Philosophie nach Herrn Feders Ordnung: 341; 347.
  

  1811

  Gesetz der logischen Affinität: jede zwey gegebene Nebenarten gränzen so an einander, daß sich ein stetiger Uebergang von der einen zur andern denken läßt. Elephant und Nashorn, Mensch und Schimpanse sind an der Erde zwey nächstverwandte Thierformen. Aber wie groß ist doch noch der Unterschied zwischen beyden, wie viel mögliche Formen zwischen beyden lassen sich noch denken.

  Fries, J.F. (1811). System der Logik: 105-6.
  

  1819

  Affinitas plantarum componitur secundum nostram sententiam tam e multitudine characterum quorumcumque in quibus conveniunt, quam ex eorum praestantia & prominentia.

  Agardh, M. (1819). Aphorismi botanici: 69.
  

  1821

  Singulum organum essentiale representat propriamclassem, ad quam referuntur ordines & genera, inquibus hoc prae ceteris evolutum. Heec classis iterum in ordines dividitur ad eandem normam, adeout, quando organum quod maxime eminet classem, dein perfecftissimum ordinem indicet. Ita & subdivisiones, quas hoc modo ortas semper cum natura, verissima Systematis magistra, conspirare expertussum. Haec dispondi ratio non tantum unica genuinanobis videtur, sed & naturam affinitatem alio modo exprimere putuisse non perspicimus. Quid enim sit affinitas, nisi characterum (organorum = classium= ordinem) harmonia universalis?

  Fries, E. (1821). Systema mycologicum, vol. 1: xi.

  1821

  Suppose the existence of two parallel series of animals, the corresponding points of which agree in some one or remarkable particulars of structure. Suppose also, that the general conformation of the animals in each series passes so graduallv from one species to the other as to render any interruption of this transition almost imperceptible. We shall thus have two very different relations, which must have required an almost infinite degree of design before they could have been made exactly to harmonize with each other. When, therefore, two such parallel series can be shown in nature to have each their general change of form gradual, or, in other words, their relations of affinity uninterrupted by any thing known — when moreover the corresponding points in these two series agree in some one or two remarkable circumstances, there is every probability of our arrangement being correct. It is quite inconceivable that the utmost human ingenuity could make these two kinds of relation to tally with each other, had they not been so designed in the creation. Relations of analogy consist in a correspondence between certain insulated parts of the organization of two animals which differ in their general structure. These relations, however, seem to have been confounded by Lamarck, and indeed all zoologists, with those upon which orders, sections, families, and other subdivisions immediately depend. Now, such can be no other than relations of affinity, since it is clear that the affinity between two neighbouring groups must become greater instead of less, as our ideas of them become less general and more simple. Every person is, I believe, aware that it is a relation of affinity which places the dog next to the wolf, as well as the Mammalia near to Birds; but then it is with the same ease perceived that the affinity in one case is much stronger than that in the other.

  MacLeay, W.S. (1819-21). Horae entomologicae: 362-3.

  1823

  W. S. MacLeay […] has first stated with clearness and precision the distinctions, so often before confounded, between real affinity and those resemblances which are merely analogical; and has proved satisfactorily, thatthere exist between numerous objects in every department of nature striking coincidences as to external characters, which do not indicate that they are related to each other, or should be placed together in a natural arrangement.

  Kirby, W. (1823). A description of some insects which appear to exemplify Mr. William S. MacLeay’s doctrine of affinity and analogy. Trans. Linn. Soc. Lond. 14, 93-110: 94.
  

  1823

  the natural affinities that connect the orders and families of birds

  Vigors, N.A. (1823). Observations on the natural affinities that connect the orders and families of birds. Trans. Linn. Soc. Lond. 14, 395-517.

  1823

  the test of a relation of affinity is its forming part of a transition continued from one structure to another by nearly equal intervals […].
  Relations of affinity being thus separated from those of analogy, we immediately get the following facts from the observation of what M. Agardh terms the affinity of Transitits, namely, that species form the only absolute division in nature, and that no groups of species (whatever may be the rank of these groups) ought to be considered as insulated, but only as series of affinities returning into themselves, and forming as it were circles which touch other circles. Such only are natural groups. This was said of Insects; and our author, looking only at plants, and principally at Fungi, comes to the same conclusion

  MacLeay, W.S. (1823). Remarks on the identity of certain general laws which have been lately observed to regulate the natural distribution of insects and fungi. Trans. Linn. Soc. Lond. 14, 46-68: 51; 53.
  

  1838

  It was the especial province of the zoologist to distinguish, in every instance, the intrinsical from the simply adaptive characters of animals; to disentangle and discriminate affinity from analogy

  [Blyth, E.] (1838). On the geographical distribution of birds. The Naturalist 3, 169-174: 171. 

  1840

  Relations of affinity and analogy have their origin in more or less perfect resemblances of structure or habits, and are of comparative and relative value; and hence that distinct relations, both of affinity and analogy, exist between the same groups.

  Westwood, J.O. (1840). Observations upon the relationship existing amongst natural objects, resulting from more or less perfect resemblance, usually termed affinity and analogy. Mag. Nat. Hist. 4, 141-144: 142.

  1840

  When by these considerations we have arrived at the notion of a natural system, composed of natural groups arranged in a determinate order, we may proceed to define affinity as the relation which subsists between two or more members of a natural group, or in other words, an agreement in essential characters. After the essential characters of such a group have been discovered and defined, then all the objects which possess those essential characters are said to have an affinity for one another. Hence we see why the idea of a natural system is necessary to the definition of affinity, for in an artificial system the characters of the groups are not essential, but arbitrary, and the relation between the members of such a group would be, not affinity, but mere resemblance or analogy.

  Strickland, H.E. (1840). Observations upon the affinities and analogies of organized beings. Mag. Nat. Hist. 4, 219-226: 221; cf. Di Gregorio, M.A. (1987). Hugh Edwin Strickland (1811-53) on affinities and analogies: or, the case of the missing key. Ideas and Production 7, 35-50.
  

  1859

  The real affinities of all organic beings, in contradistinction to their adaptive resemblances, are due to inheritance or community of descent. The Natural System is a genealogical arrangement

  Darwin, C. (1859). On the Origin of Species: 479.
  

  1910

  Affinität – Das Wort bezeichnet im Lateinischen deutlich die Nachbarschaft, in der juristischen Gemeinsprache die Verwandtschaft durch Heirat, also Verschwägerung im Gegensatze zur Blutsverwandtschaft, cognatio.

  Mauthner, F. (1910). Wörterbuch der Philosophie: 14.