Is there an atheist in the house ? (its regarding my Circular Saw)

Ive got a very old Circular Saw in the garage which i dont need (and I
suspect it knows that i dont need it...as it has become obsolete in
design and has suffered quite a few mutations during its useful life). I
could however make very good use out of a Jig Saw for various projects ;
Therefore, Im wondering ... if the environment is right (ie: sawdust on
the floor and wood laying on the shelves) , the ambient temperature is
favorable, electricity is available, and many of the same fundamental
parts exist between the two.... how long could I expect the Natural
Selection process to take in order to produce a fully functioning Jig
Saw from the materials therein , and of course, giving it all the time
necessary to make the required transition ? =A0 I dont expect to witness
the transition process and i promise i wont peek in the garage to see
how its coming along. =A0 Thank you.
 
P.S. * Im not looking for a variable speed Jig Saw...just a single speed
Transitional Unit will suffice.