We know that they sing, sending musical waves through the deep as they travel in complex family units. We know that they appear stricken with grief when one of them dies. And now we know that the great whales of the world are capable of loving.
A remarkable new study will reveal that whales - hunted for centuries by man, and lauded in ancient literature for their mystical qualities - have the ability to experience love and also deep-rooted emotional suffering.
Two scientists - Patrick Hof and Estel Van Der Gucht, of the New York Consortium in Evolutionary Primatology - made the breakthrough after spending 15 years studying the brains of the biggest mammals on the planet.
They did not expect to find anything unusual when they set out to study the inner workings of the large whale brain. But the scientists were determined that humans should know more about the minds of these mysterious creatures.
They discovered something that could change the way the world views whales, which are still hunted by Japan and Norway for "scientific purposes". As they studied a brain, they came across a spindle cell - a cell originally thought to live only in humans and great apes, and which allows humans to experience love and emotions.
Professor Hof told The Independent on Sunday: "I really wasn't expecting this. I stumbled on one by chance and I said, this looks like a spindle cell. Then I saw them everywhere, and I immediately realised that we had something big."
The spindle cells were found in humpback whales, fin whales, killer whales and sperm whales - all the whales that have large brains as well as large bodies. The discovery not only means that humans and apes aren't the only ones who have these distinguishing spindle cells, but that primates were not the first to have them.
It appears that large whales have been evolving these cells for 30 million years - twice as long as humans, according to an article in New Scientist ahead of publication of the scientists' findings.
Whales also have more of these emotion-controlling cells, and early research indicates that they may have up to three times as many spindle cells as humans. In humans, these cells help process emotions and encourage the development of social interaction.
But even though the cells allow humans to feel love, more work will be needed to judge whether love is the same for humans as it is for whales, Professor Hof, the vice-chairman of the department of neuroscience, said from his office at the Mount Sinai School of Medicine in New York.
"I don't know about love or emotion," he added. "I don't know the nature of such feelings in these animals. Whales are isolated and we cannot just apply what we see in great apes or ourselves in that type of animal. It's very difficult to know. Many people would like to say that, of course."
But these spindle cells were found in the same area of the brain that regulates emotional functions such as social organisation, empathy, speech, intuition, and rapid gut reactions in humans - the anterior cingulate cortex and frontoinsular cortex. Large whales do show some of these characteristics, making the findings even more significant to the academic. Cells were also found in other areas of the whale's brain, but Professor Hof doesn't know the significance of these finds.
He said: "What is fascinating about the species these cells were found in, is that you have the capacity for frequency and specificity. They can communicate in an intelligible manner. Hunting parties are very well co-ordinated. You can see killer whales teaching hunting techniques to their offspring. It's quite striking."
Professor Hof is still investigating exactly how spindle cells function in whales, but for now he believes that long, high-speed connections fast track information to and from other parts of the cortex. The quick connection allows for instant processing and appropriate emotional cues for given situations.
After discovering the spindle cells in whales, Professor Hof is to look at other large animals. He is currently studying elephant brains, and said he expects to find spindle cells.
This type of research was crucial, he said, and when it came to large whales, more of it needed to be done. "They are difficult to track in the ocean, but it's worth the effort. There's so much that humans just don't know about large whales, and any information that comes out can only make it easier for people to help protect and conserve these mysterious animals.
"They are certainly popular animals in general, but they are all threatened and live in habitats frequently quite endangered. We just don't know enough about their biology."
The scientists' report will appear in the January edition of The Anatomical Record.