My understanding is that Ubuntu is based on Debian. For example, on the Wikipedia page for Ubuntu it states "It is a Linux distribution based on the Debian architecture." How can I find out what version of Debian a particular version of Ubuntu is based on (if any)?
For example, the current stable release of Ubuntu is "Artful Aardvark" (17.10) which announces that it is based on the Linux 4.13 kernel, but does not seem to say anything about the Debian version.
The current stable release of Debian is code named "Stretch" (9.2) which advertises a 4.9 kernel (on the afore-linked Stretch page). How can I find out the details of the relationship between them? Is there a particular command that will reveal this information?