Fitness Causes Bloat

1. Search starts with short trial progs  
2. Rate of improvement quickly falls  
3. Fitness selects best in population  
4. 2. & 3. Fitness selects children which behave like their parents  
5. There are many more long programs than short which behave the same  
6. 1. & 4. & 5. Selecting one at random is likely to be longer than its parent
   I.e. Fitness causes bloat