I have noted before that evolutionary networks are used in both biology and the social sciences, and that you will also occasionally find them elsewhere, as a means of displaying historical relationships among objects or concepts (see this blog post: Phylogenetic networks outside science). However, the uses outside science are not always successful, as shown in this previous blog post (Direction is important when showing history). Here I discuss another example of a phylogeny of ideas rather than objects that has potential problems.
This is labelled as a Computer Languages Timeline but, just like the previous example of a GNU/Linux Distribution Timeline that I discussed, it is actually drawn as a set of linearized genealogies. These are evolutionary networks rather than trees because there is horizontal transfer (ideas added) and recombination (ideas replaced) among the languages.
|Click to see the original image.|
The basic problem with this example is that it is not time-consistent. That is, the connections between languages begin at one time and end at another time. This does not happen with the GNU/Linux example. Many of the connections seem to have arbitrary begin/end times, which is not only unnecessary but also confusing.
There is, however, a good reason for some of the connections not being time-consistent. This occurs when a previous version of one computer language is used as the source of ideas for a later language, so that the information does indeed travel through time, in the manner that I have already discussed for phylogenies of ideas rather than objects (see this blog post: Time inconsistency in evolutionary networks). Examples in the Computer Languages phylogeny include the use of Fortran I (1956) as the basis for IAL (1958), and the use Fortran II (1957) as the basis for Basic (1964).
It is important to distinguish these two types of time inconsistency. There is a logical basis for the transfer of ideas through time, in which case the reticulation connections should be drawn to reflect the time inconsistency; but there is no logical basis for the other time inconsistencies, and their use should be avoided in the diagrams.