Skin and non-adhesive cells found to play pivotal role in formation of fingers. Human fingers are sculpted from a primitive pad-like structure during embryonic development. Sometimes, this process goes awry and babies are born with fused fingers or toes. A new study reveals new factors involved in the congenital malformation called syndactyly. Source 8t.
This is kind of the proof that genes are basically the 'formula' that specifically designs how the body should operate. But somehow, if the chemical components (Which is sort of the 'writing' of the formula) does not synergize or come on time it'd simply cause a strange mutation that goes badly!