Correct Usage of IT

[sujit2k7]

I am really confused with IT as pronoun and IT as a placeholder.

let's pick GMAT SC question:

Descending approximately 4,000 years ago from the African wildcat, it has
been an
exceedingly short time for the domestic cat with respect to genetic
evolution and it scarcely
seems sufficient to allow the marked physical changes that transformed the
animal.

I discarded this option on the basis Modifier does not follow the noun it
is modifying(who ? the domestic cat).
But i felt usage of IT is correct as such. I thought both the below are correct ICs.

it has been an exceedingly short time for the domestic cat with respect to genetic evolution
it scarcely seems sufficient to allow the marked physical changes that transformed the animal.
Am I correct here..
Where should i search for antecedent of IT and where not

[tim]

What do you think the antecedents of the "it"s are? Did you read the explanation for this one? Most questions you could have are answered in the official explanation..