Ideed, it is a complicated thing, love. A biological trick to propogate the species. But that in of itself means it is there. It's origins are moot. All thought is but chemical and electrical discharges and exchanges in the brain. But this does not mean you do not think. It does not mean you are not "real". God is real to some. That is their perception. If another does not precieve Him/Her/It to be real, does that make Them any less real to the first person? This does not change what reality is, even if reality is perceived differently by different people. Likewise, just because love is but a simple trick of nature does not change the fact that it is there.
Sometimes I scare myself. He, he, he.