We are genetically conditioned to love those that share our bloodline (family) and those that would make a good mate (romantic).
Love is the mechanism through which our species guarantees its survival. The way we fall in love, who we fall in love with and how long we stay in love for are all focused on producing healthy offspring. Love is simply a mechanism through which the human race ensures its future existence and allows us to pass on our genes.
The laws of love are predetermined by genetics and evolution. We are programmed to love those that come from the same bloodline as us. Therefore, we instinctually love our parents, our siblings and our children. When we find a potential mate, we naturally are predisposed to fall in love with those that would provide the best offspring. Universal standards of attractiveness can all be traced back to evolutionary terms. Men with big muscles, broad shoulders, and narrow hops might be considered attractive because they can protect the female and the offspring. Some women may be attracted to men with money because they believe it means they will provide for their offspring. A youthful looking woman might be considered more attractive because women are more fertile in their 20s than in their 50s, for example, and it subliminally informs males that she may be able to give them offspring. Once we choose a mate and a child is conceived, often a monogamous relationship forms. This is also a product of our desire to pass on our genetics. In most primates, a mother will not mate until her infant has weaned. In the animal kingdom, a male who wishes to mate with the mother will kill the infant. However, almost a third of primates form monogamous relationships with the other parent of their child. They do this to prevent other males from killing their infant. Researchers at University College London believe that this is how monogamy developed over 20 million years. Love is evolution. It is the manifestation of our species determination to survive and flourish. There is nothing more to it than that.
This narrow definition of love excludes forms of love which are not blood-linked and do not have an inherent desire to reproduce. By this definition, same-sex couples would not be able to experience love. Nor would an adoptive parent for their adopted child. There would also be no room to love a friend or a pet. Love cannot be reduced to reproduction and science. It is far more complex. Sometimes, as in these cases, people love just for love's sake.
[P1] Monogamy, choosing our partner, and universal standards of attractiveness are predetermined by genetics and evolution. [P2] Love is the way our species reproduces and evolves. [P3] Therefore, love is just science and reproduction.
[Rejecting P1] Not all forms of love are reducible to reproduction and genetics. [Rejecting P2] People can also love just for love's sake.