From: Hans-Cees Speel <hanss@sepa.tudelft.nl>

Some information about the essay of Hull;
It follows the following points:
the difference between reference classes, and particulars
[historical entities], and explains that an evolutionary theory 
differers from most theories by being concerned with the latter.
After this he compares the theories of evolution in biology, and in the social sciences [read theory of memes].
There he argues that:
- biological species are not classes, so can be compared to memetic evolution
- social evolution is only in a verry shallow sence lamarcian
- socialcultural evolution has an important intentional element that 
biological evolution has not.
In the end he touches the concepts of replicator, interactor and lineage, that 
I believe are the best concepts to be used to compare biological and social-cultural evolution.

Hans-Cees