Not yet. We were more talking about sexual attraction. Not attachment. So let's do that now.

Let's zoom in, from the point of view of the specie, to that of the individual.

I will talk about this very easily identifiable feeling that we could define as : “When I think of him/her, I'm on cloud nine”. That should leave little space to ambiguity. We will try to avoid the term “love”, that is way to vaporous.

It is pretty obvious that this feeling is of a different nature than friendship (attachment to a peer) or the attachment we feel for a toy, an ipod or a pet. It presents almost all the characteristics of a reaction to a psychoactive drug. A psychoactive drug triggered by a conscious thought, or and inconcious process triggering both.

If indeed it is an hormone, then its raison d'être is genetic evolution. Each one of our hormones appeared under the pressure of evolution. An easy solution takes shape : One intercourse is not always sufficient to impregnate a female. By supplementing the "attraction hormone" with an “attachment hormone”, it is made sure that a female conceives by making her mate repeatedly with one male.

It is not beneficial to make the effect last more than a month, because if after a month of relentless copulation there is no pregnancy, it is unlikely that there will ever be one. That is why the attachment that we feel evaporates after a while, to allow its victims to look for a partner somewhere else.

So, yeah, love is an hormone.