Why we can be sure Adam was a historical individual

Professor James Anderson (no relationship, well, unless you go back most of the way to Adam the historical individual...) gives a good concise summary of why evangelicals are compelled by the Bible to view Adam as a single historical individual in the same sense as you or I are: http://proginosko.wordpress.com/2009/09/21/was-adam-a-real-historical-individual/ . With a footnote offering a 13th that he forgot about the first time round!

Here's a conversation I had at the registry office whilst registering my intention to marry my now-wife. Earlier conversation had established that the registrar was a church-goer... perhaps it had been a slow day...

Registrar: Are you related to your future wife?

Me: Only through Adam.

Registrar: Your son?

Me: Ha ha! No.