Why do we all have finger nails and why do they develop so quickly on a foetus?

Question: Why do we all have finger nails and why do they develop so quickly on a foetus?
- Keywords:
  finger,
  foetus,
  nail
Asked by gwen626 to Daphne, Darren, Jon, Katherine on 21 Mar 2012.
- Katherine Haxton answered on 21 Mar 2012:
  
  Finger nails are probably what’s left over from claws that the animals we evolved from had. They would need them for defence, getting food and other stuff. They probably develop quickly on a foetus because the fingers do, and they are the last bit of the fingers.

Question: Why do we all have finger nails and why do they develop so quickly on a foetus?