The purposes of the lectures were:

Many of the concepts and assumptions we use every day were established long time ago and often in another context. The correlation of one or a few characters with a class of organisms was established in prehistory as part of 'defining' our language. This can give classifications that do not reflect genealogy and ignore other properties- f.ex. whales being classified as fish because they live in water (common until late 18th Century). The concept of 'species' was invented in late 17th Century, greatly modified around 1930 by the evolutionary systematists, and we had some fun trying to find out what is REALLY a species. Evolution was invented by Lamarck (some of the old Greeks and Romans actually claimed some sort of evolutionary processes, but these were ignored/forgotten later), Cuvier established fossils as remains of extinct organisms.

We can construct explicit evolutionary hypotheses - trees, depicting the relationship of organisms - by analysing explicit data (anatomy, DNA, crystallography, morphology, age, ....) with reproducible methods (cladistics, stratophenetics, maximum likelihood, ...). These do not give us the 'truth', but will always be reproducible, and can easily be supplemented by adding data. These methods eliminate considerations of 'good' and 'bad' data.

With an explicit phylogenetic hypothesis, we can interpret biological phenomena. We can determine whether one or two horns in rhinoceros is 'primitive' (the correct term is 'plesiomorphic' or 'ancestral' - there is no quality stamp on nature), whether taxa (species, if you like) in a group of islands are due to multiple invasions or local diversification, whether hosts and parasites co-evolve or result from multiple events. Explicit phylogenies give us good classifications, but are also essential tools to interpret data.

Biologists are always asked 'why' - 'why does the elephant have a trunk', 'why are there 15 species of Mumbidae on this islands', 'why do foxes eat rabbits', .... Nobody asks a chemist 'why are there two hydrogen atoms in a molecule of water.' Phylogenies allow us to answer the 'why' questions, and the answer is often something like 'because its ancestor did'. Most of our observations are due to history; if a certain relationship was established by an event, this event often took place long time ago, and if you wish to discuss the event, you must know when, where, and in which context it took place. An elephant has a trunk, because its ancestors had trunks. If you trace the evolutionary history of elephants, you will find an ancestor without a trunk, and the even - evolution of trunk - took place at that time and place. If there is any causal relationship between an event and the evolution of trunks (adaptation, selection, ...) it has to be established at that point.

You will find copies of most of the overhead transparencies used during the course posted on the web site http://pecdc.univ-lemans.fr/class/Phylo2000/ You are welcome to use these for review, and may obviously print or copy them for your personal use.