Hi Barabara,
I think you have things a little confused. There is no such gene as Olfactory, what there are are a large number of distinct olfactory receptor (OR) genes, which encode a variety of different membrane bound receptor proteins.
What we find with these genes is not what you state, Humans have roughly the same number of functional OR genes as chimpanzees. There are ~400 human OR genes that appear to be functional as protein coding genes and ~353 similarly functional OR genes in the chimpanzee (
Gilad et al., 2005).
Exactly what you are talking about is unclear.
TTFN,
WK