Evolution of malformation...

I remember seeing a television show in the early 80's that interviewed two or three African individuals with ectrodactylism -- a rare hand and feet deformity that leads to two or three toed feet with webbing.

The question the image poses is -- are genetic anomalies like this the type of mutation that leads to evolutionary traits or is this just a random deformity?

Wiley InterScience: Journal: Abstract