A human creation (yes a human creation) that involves a relationship usually between 2 persons, or more depending on the culture (There are places in the world where you can have more than 1 wife you know.)
Love evolved from being pure sex at the younger state of the human back in prehistory, then through societies were born, the idea of living as a couple came up as a way to live more easily (and possibly have sex more easily) and as time went by, the different cultural influences over time brought love to what it is today, although it differs from country to country, and from person to person: to some of them it is only sex, while to other its a huge "feeling" that has nothing to do with sex. Even though love started from sex, we "created" it into something that has more or less to do with sex. Through these cultural influences, people limit their possibilities in life by putting "invisible laws" such as "no sex with other people", "only one lover" as the idea of making someone "one special person" is very big, and there is much more restrictions to love than those 2.
In north america, love is usually a "strong feeling" towards another person, people get to know others usually before "Going out" and their love is based off something else than sex, although sex is included in the extremly huge majority of couples.
In Japan, people go out before knowing eachother and they learn about eachother after.
In some islamic countries and India(?) , men can have several wives. This is NOT "fucked up", this is normal to them, do not take something as a real truth because you have been seeing only one side of the story your whole life, be open.
Many philosophers and psychologists think love is a human creation, my psychology teacher even said "the only difference between love and friendship is sex" , which is definitly true. This refers to my "restrcitions people put on themselves with love" however.
Now, if you believe love is a human creation, youd probably be better not telling it to your girlfriend if shes not open minded and crazy about love, because she'll probably go apeshit like my friend's girlfriend (although it was only for a second)
A theory i have about the evolution of love: My french teacher told us about people starting to treat women nicely back in the middle ages, I forgot how they were called, but it was back in the years 1000ies. Those people pretty much just flirted with the girls, doign nice things for them etc. If you read old books from the middle ages, you'll see that the extremly huge majority of books (at least ive never seen one thats different..) show love just as being a physical attraction and nothing more, men love women because they are beautiful, women love men because they are beautiful or they saved their life somehow, this shows the evolution of love and is probaly another determining point that led to the love we have today.
Remember, even if i say love is a human creation, i don't say love doesn't exist, we invented it and therefore it exists. Too many people tell me "Well i think love exists so i don't believe it is a human creation". Love being a human creation does not make it lame or worse, if anything this probably makes your understanding of love much better as you'll actually be eable to explain it. Love is still a wonderful thing and im happy for every lovers out there (of course, the lovers who live in a culture where love is a good thing ^^)
Prehistory men love for sex alone, people in the middle ages love for sex and possibly friendship (in other words fuckfriends), and today we love for the personnality of others (well the majority, right?).