GNU/Linux distro timeline (svg)
upload.wikimedia.org
upload.wikimedia.org
Current models do not exactly apply.
Highlighting the lineage aspect, however, loses useful context information. For example, Robert Shingledecker was a significant part of the development of Damn Small Linux for five years before he started the Tiny Core Linux project. While there's no commonality in the distribution-specific code that I'm aware of, and hence no reason for a graphic connection on the chart, I think it's safe to say that Tiny Core's design is a continuation of Shingledecker's thinking on what makes a good minimal Linux.
It's interesting to see that most distros are descended from either Debian, Slackware or Red Hat. I guess that trying to improve what already exists is less work than starting one from scratch.
Slackware originated from SLS. So strictly speaking SLS and Red Hat appear to be the two originating distro's from others have decended in one way or another.
I used linux for 5 years and used redhat in 2001, gentoo for a brief time, slackware for 2 years, fedora for a year, back to windows for 1 year and now I'm a happy OS X user for 3+ years.
I can sympathize with the irritation of seeing duplication of effort. But when that irritation pushes a mind toward the tempting presupposition of some single measure of goodness which could have been a guiding light the whole time, paring away effort duplication and dead-ends... well, the thinking has gone a bit absurd.
There are many regions of possible-OS space, not everyone needs or wants to be in the same one.