The question of complexity is classic in the very first lectures of evolutionary biology where the teacher usually tries to tell the students that complexity does not necessary increases and that humans are not more complex than other organisms.
My questions are:
- Why does complexity tend to increase through evolutionnary times?
- What are the different hypotheses to explain this pattern?
When writing "Mass extinction" on google image, we find many graphs displaying the number of families (or other taxa) through evolutionary times with the 5 Mass exctinctions. What would it look like to draw such graph replacing the family richness in the y-axis by :
- Mean complexity among all living things?
- Complexity of the most complex taxon?
I supose that, one who wishes to answer to this post will necessarily needs to define the words "complexity". He/she might define it in terms of number of genes, number of metabolic pathway, length of the DNA sequence, number of cell types, some kind of index taken from information theory, ...When asking my questions I had in mind a definition close to "number of genes" or "number of metabolic pathways".