Emotions do exist in animals. But the in general, the emotion you call love, does not exist. Even not in humans. It is a hard thing to think about, but it is here because we want that emotion to exist.
Science has proven that animals do indeed feel emotions. All emotions are driven by hormones. Positive emotions are driven mainly by dopamine and endorphins, while painful emotions are driven cortisol.
I believe it is easy to agree that animals feel fear, and most people have seen an abused dog cower in the presence of a human, so I will focus on the other end of the spectrum: love. Love, in all of its forms, is driven by oxytocin. Mothers and babies show increase oxytocin levels immediately after breastfeeding. A lack of breastfeeding has been correlated to reduced bonding between mother and child. At a wedding, all attendants have increased oxytocin levels as well. Many in-depth studies have been done on the human-canine relationship. One such study stuck two strangers (one human, one canine) in a room. A half-hour petting session ensued. Oxytocin levels were measured in both at the beginning of the experiment and at the end. Both parties has significantly heightened oxytocin levels afterwards.
Now, animals have varying oxytocin responses, depending on the location of the receptors. A famous example of this are voles. The meadow vole is a polygamous species of rodent (I'll spare the actually neurophysiology), and the prairie vole is a monogamous species, very closely related to the meadow vole. The oxytocin receptors are in different locations of the brain. A gene therapy was done to cause the meadow vole's receptors to grow in the same location as the prairie vole's, and vice versa. Amazingly, the previously monogamous prairie voles became polygamous and the meadow voles became monogamous with their current sexual partner.
It is well established that oxytocin is present in mammalian species, and more and more discoveries about oxytocin and love are made each year, so how can one say animals don't feel love?
There's every reason to expect animals in general to have emotions, just lacking the layer of mental planning where humans anticipate the future or have things like mid life crises.
Brain anatomy generally tells you that reptiles have all of the anger and selfishness type emotions and mammals come equipped with the empathy set of emotions. Social mammals have a somewhat wider set of emotions from things like being in close proximity to rivals as a matter of daily life.
Gets difficult to make precise comparisons of emotions between similar species though.
IMO we evolved from the same cell so saying were the only beings with emotion would be like saying were more advanced so were the only beings who breeze. I also think that God gave all living things a soul so if so then yes they would have emotions. Depending on what you mean by cry certain animals don't have tear ducts. Others have the instincts not to make noise out of pain because it can attract predators. Some animals will basically get married and never separate and not "remarry" if the partner dies. So yes I think they have emotion because it would be nearly impossible for some of them, if not all to not have emotions.
Put humans in a box with water but no food and see how it takes until they start eating one another. Don't do that but the point I am trying to make is that humans are just as instinctive as other animals for the most part. love is a term that is used to describe a complicated set of emotions. Primariliy love is used to describe attachment and attraction. It is safe to say that we experience the same emotions that cause a dog to wait anxiously for its master in the same way that so many guys wait anxiously for their girlfriends to text them.
Human emotions were probably developed the same way an "animal"'s was, you know. Humans are animals, too.
The only reason we feel - or what you say, love, and cry - is because we needed to bond to one another for survival. We love so we would stay together. We cry so we would not fall apart. Human infants can't take care of themselves for years; long-term bonds and empathy are evolutionary necessities. Do you think for a second that if humans were born completely self-sufficient, they would care for one another the same way we do now?
Though (most) animals are less mentally developed than (most) humans, so for that reason only, I doubt their feeling capacity would be as strong as a fully-developed human.
A gene therapy was done to cause the meadow vole's receptors...
That's reeeeeeeaaaaaaaallly cool. Do you perchance have a link to this study? I'd love to read it!
We are just beginning to delve into the world of animal emotions. I think it's safe to assume creatures such as the sea sponge probably do not feel much, emotionally, seeing as they lack brains or any real social contact. Emotions exist, I think, to facilitate interaction with other individuals.
Why do we choose monogamous relationships (mostly)? Because we feel romantic love for another individual? I can't think of any other reason. Societal pressures, maybe, but those must come from somewhere. Neurophysiology aside, why should we assume, then, that any other creature has a different reason for monogamy?
Recently, I've heard a lot about grief. There was a video somewhere, not long ago--I might try to hunt it down and include it here--of a gorilla who speaks sign language being told that someone who visited regularly had died. She didn't see this death. It hadn't been long enough for her to assume something had happened, or to miss experiencing time with this person, but when her handler told her, via sign language, that this person had died, she made the sign for 'tears' with no prompt from others.
When elephants come upon an elephant skull in the desert, they gather, rub their trunks around the bones, and then bury them before moving on. I can't see any evolutionary benefit for this. It seems to me that when they do this, they are grieving.
Two dogs live together for a number of years. When one dies, the other becomes extremely lethargic, loses interest in things like chasing balls, and often stops eating. This is pretty common. Why do they do this? Depression-like behavior seems like a very bad instinct to have, if mere survival is your only goal.
There was even a study on birds--bluejays, I think--following the observation that when a dead jay is found on the ground, other jays in the area will gather and begin cawing. Some blue wood arranged to look somewhat like the form of a dead jay did not induce this response, but seeing the body of a fellow bluejay did. This could perhaps be an evolutionary trait; one can see how alerting other members of the species of potential hazards in the area could come in handy. But inasmuch as emotions are a reaction to external stimuli, I'd say that's something. It certainly shouldn't be ruled out.
Now, as several others have stated, emotional range will depend on the animal. Ants, for example, are extremely social creatures but they exhibit no real attachment to their fellow ants. If one ant starts to show signs of a fungal infection, it will quickly be carried far away from the anthill to die where the spores cannot spread through the colony. I've never been inside an ant colony, but I seriously doubt they follow this up with a moment of silence for their fallen comrades. The ants in my kitchen certainly don't exhibit any visible behavioral changes when I start raining toxic death upon them.
Dogs with abandonment issues experience sometimes quite severe bouts of anxiety when their friends leave. Purely anecdotal, but I heard there is a dog in Italy who, when his owner passed, continued to find his way to the church every Sunday morning. Maybe it was just habit. Maybe not.
I don't expect my beta fish cared what happened to me. I never saw any indication of love or hate or anger from my rabbits either. But I know my dog sighs when someone says the "w" word but doesn't fetch her leash, I know she wags her tail when someone says her name in a happy tone and she drops her gaze when someone shouts it, and I know she smiles at me when I wake up in the morning. That's proof enough for me.
Personally, I know my cat can feel emotions. He's sad whenever me or my girlfriend go to work, as he tries to get in our way with big, watery eyes to try and stop us from leaving, and when we do leave, he attempts to follow until we're out of sight and pouts as he flops to the ground in defeat.
Alternatively, when we get home, he bounds over to us with the biggest smile on his face. biggrin
Cats are pretty complex critters though, so that may not be a fair comparison.
I believe that, yes all animals are able to feel and express emotion, but many do not get that chance due to environmental factors. If we look at Maslow's hierarchy of needs it states that at the bottom is the physiological needs, followed by safety, since most animals are either hunting or trying to keep themselves alive they don't fulfill the two lower needs needed to achieve the more complex needs.
For example we've adopted strays off the street and it's taken them months before they felt truly secure in our house. That's when they start to exhibit a personality. I know animals can feel emotions because my cat cries when I'm gone, she greets me at they door, she mews happily when I call her to bed and she watches tv with me. As for another, I scold her and she 'yells' at me.
Their emotions may not be as complex, but they are there.
Science says yes, yes they do. Why...>_> that' s a whole can a worms I don't feel like opening up. But for what it's worth, I did read (Animal Rights Morality by Bernard Rollin) this book that was enlightening and asked this very same question and the issues that come with it (as in, there are actually at one point some ignorant scientists who believed animals do did not feel pain...which insulted to me to no end cuz I am biology major).
But just fyi, the book (IMO) was somewhat one sided but overall it's an interesting read for anyone who is into animal ethics.