Thanks.
Just for the record I'm going to answer the question EP was afraid of.
Obviously a teacher would find it difficult to prove cheating by comparing essays if the students simply claim that their identical answers are just a result of using the same sources.
In a similar way creationists claim that the amazing correlation between animal genomes are simply a result of having the the same creative source.
Our professor has a simple technique available to confirm her suspicions. By carefully comparing the errors in each essay plagiarism can be proven beyond all doubt. For example if all the students write that the first world war began in 1975 it is inconceivable that they did not cheat - there are countless ways to be wrong!
In the same way it is by examining the tiny quirks in genomes that we can prove common ancestry. For example very occasionally a virus will get itself copies into a sex cell of its host and be copied into future generations. The exact place where this viral DNA ends up is almost - but not totally - arbitrary. When we find the same viral DNA in precisely the same place in species, and when we can repeat that for multiple endogenous retro viruses, we have proof that those species share a common ancestor.
This is very similar to the proof that is used in courts every day to prove paternity and convict rapists.
This is the difference between science and ideology. This is why ideologues like EP run away from actual debates.