  Phylogenetic approaches to classification have been heavily developed in
biology by bioinformaticians. But these techniques have applications in other
fields, in particular in linguistics. Their main characteristics is to search
for relationships between the objects or species in study, instead of grouping
them by similarity. They are thus rather well suited for any kind of
evolutionary objects. For nearly fifteen years, astrocladistics has explored
the use of Maximum Parsimony (or cladistics) for astronomical objects like
galaxies or globular clusters. In this lesson we will learn how it works. 1 Why
phylogenetic tools in astrophysics? 1.1 History of classification The need for
classifying living organisms is very ancient, and the first classification
system can be dated back to the Greeks. The goal was very practical since it
was intended to distinguish between eatable and toxic aliments, or kind and
dangerous animals. Simple resemblance was used and has been used for centuries.
Basically, until the XVIIIth century, every naturalist chose his own criterion
to build a classification. At the end, hundreds of classifications were
available, most often incompatible to each other. The criteria for this
traditional way of classifying is the subjective appearance of the living
organisms. During the XVIIIth a revolution occurred. Scientists like Adanson
and Linn{\'e} devised new ways of classifying the objects and naming the
classes. Adanson realised that all the observable traits should be used, giving
birth to the mutivariate clustering and classification activity (Adanson,
1763). Linn{\'e} based his binomial nomenclature on neutral names unrelated
whatsoever to any property of the classes. We can realise the success of these
two ideas more than two centuries and a half later!
