Astrocladistics, a methodology borrowed from biology, is an objective way of
understanding galaxy diversity through evolutionary relationships. It is based
on the evolution of all the available parameters describing galaxies and thus
integrates the complexity of these objects. Through the formalization of the
concepts around galaxy formation and evolution, and the identification of the
processes of diversification (build up, secular evolution, interaction,
merging/accretion, sweeping/ejection), galaxy diversity can be expected to
organize itself in a hierarchy. About 500 galaxies described by about 40
observables have now been analysed and several robust trees found. For
instance, we show that the Dwarf Galaxies of the Local Group all derive from a
common ancestral kind of objects. We identify three evolutionary groups, each
one having its own characteristics and own evolution. The Virgo galaxies
present a relatively regular diversification, with rather few violent events
such as major mergers. Diversification in another sample made of gas-poor
galaxies in different environments appears to be slightly more complicated with
several diverging evolutionary groups. Work on a large sample of galaxies at
non-zero redshifts is in progress and is pioneering a brand new approach to
exploit data from the big extragalactic surveys.Comment: To be published online at http://www.sf2a.asso.fr