Kottke sums it up:
Someone draws a straight line. The next person's task is to trace that line as precisely as possible. Repeat 500 times. The lines get really messy surprisingly fast. As David said, this is a nice demonstration of evolution.
Patrick James goes further:
Chaos is just marvelous, no? The entire effort communicates something essential about what it means to be human. Each misplaced contour seems to whisper the immortal words of Samuel Beckett: "Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better."