There is something startling about an elephant's eyes.
Their fiery amber color seems to blaze against the surrounding skin's burlap creases. An ancient face, lined with history, but it is the eyes that convey the generational knowledge of the species. They offer a glimpse into what researchers now say is a surprising level of consciousness. It is one of many reasons why the place elephants hold in our imaginations is both epic, and wondrous.
Watch the story Friday on "20/20" at 10 p.m. ET
"There are things about elephants that seem so similar to us. Their family life, their emotional life, the fact that they grieve. They stand out from other animals," said Gay Bradshaw, director of a research institute called The Kerulos Center.
Field scientists have studied the special bonds of elephant herds for decades. Family members mourn their dead, even gently caressing the jawbones of their ancestors during grieving rituals.
Filmmakers have also documented moments of pachyderm heroism, as when a herd of adult females rescued a baby elephant that had fallen into a mud hole, remarkably forming their own team of first responders.
And in a poignant demonstration of similarity to humans, an elephant named Happy at New York's Bronx Zoo recently joined the ranks of self-aware species that includes humans, apes and dolphins. Happy showed scientists something profound when she passed the test for self-recognition: An understanding that the elephant in the mirror … was her.
"I think the real shock right now, in terms of the mirror self-recognition tests and their intelligence and their emotions is, they're like us. It's not that they're way up there. It's that they're on level footing with us," said Bradshaw.
But even as science holds a mirror to our similarities, in recent years researchers have observed a violent change in elephant-human relations after decades of peaceful coexistence.
"Humans are regarded as the enemy. You must never, ever be cruel to an elephant because they have an amazing memory. They will remember that for life. And they bear grudges," said Daphne Sheldrick, a renowned wild elephant expert and director of The David Sheldrick Wildlife Trust.
Creatures who seem to share the best of what makes us human are now revealing they are also capable of the worst.
One of the most terrifying cases took place in a circus tent in 1994, when Tyke, an African elephant, mauled her groomer and trainer.
It was a modern-day version of King Kong eerily come to life, when Tyke escaped into the streets of downtown Honolulu, seeking refuge from the gathering armies of law enforcement, until she was eventually gunned down. It took 87 bullets.
"The Tyke footage is particularly disturbing when you look through the eyes of the science, because you understand the behavior that Tyke displays is someone who is incredibly stressed, someone who is so traumatized and so upset. It's very un-elephant like behavior," said Bradshaw.
Elephants have ample reason to fear humans. In the last century their population has been decimated, from an estimated 10 million in the early 1900s to half a million now.
They are slaughtered for the ivory and sport hunting trades, or captured for zoos and circuses. Generations of orphaned herds have become broken, so unlike themselves -- now aggressive and depressed. Bradshaw and her fellow researchers have made a diagnosis that was once thought to be uniquely human: Post Traumatic Stress Disorder.
"To diagnose an elephant with PTSD is novel, but that's because we have denied elephants the capacity of having a mind, having emotions. All the neuroscience says, yes, it's there, and the behavior confirms it," Bradshaw said.
Bradshaw and her colleagues published these startling findings in the journal Nature.
"How an elephant can be traumatized is seeing, for example, their mother killed with a gun. It's a huge shock," Bradshaw said. "Being taken away from their family, taken away from the herd and put into captivity."
For many elephant orphans, surviving capture is only the beginning of their journey out of Africa, and into a new heart of darkness.
"The trauma stays with the elephant when they're in captivity. They adapt to the life. That's a survival mechanism. Just like human prisoners. Some people can survive, some people cannot," Bradshaw said.
Sheldrick said she has seen how the elephants change.
"When you look at a miserable captive in a zoo, you're not seeing an elephant. You're seeing a tragedy," Sheldrick said.
A tragedy for what elephants have experienced, such as dominance training sessions in some facilities, and what they have not: the space to roam without boundaries.
"One hundred miles is a little stroll to an elephant. You can never give an elephant enough space in a zoo. It's like putting a human being in a matchbox for life," Sheldrick said.
For the last 30 years Sheldrick has been rescuing baby elephants orphaned and traumatized by the bloodshed of poachers.
"When they come in, newly orphaned, they have nightmares at night. They wake up screaming," said Sheldrick, who has become a surrogate mother at The David Sheldrick Wildlife Trust in Nairobi, Kenya, her orphanage for elephants. "The elephants have been the greatest challenge that I've had to face. Because at any age an elephant duplicates a human. When you take on an elephant, it's actually a lifetime's job."
Sheldrick and her devoted team nurture the babies back to physical health by feeding them milk every three hours, and back to emotional health by teaching them how to play and bond with new friends.
The keepers even sleep with the orphans at night, becoming a surrogate human family so that one day the elephants will be strong in spirit, and ready to join wild herds again.
"They have to be psychologically sound, because the wild elephants don't want a problem," said Sheldrick.
But there are some babies Sheldrick can't save. Elsewhere in the world, nursing elephants are separated from their mothers, their spirits broken in secret training camps so they can be taught to give tourists rides.
For decades, animals in the entertainment industry have been made to perform behaviors never seen in the wild, and the weight of captivity is bearing down on even the mightiest of animals.
"They're essentially very gentle animals. So for an elephant to become aggressive and kill a human, you have to understand how badly he's been treated by humans to be able to pluck up the courage to do that," Sheldrick said.
But something revolutionary is happening in the flatlands of Tennessee. Deep roars can be heard through trees that shield neighbors from an unlikely sight, one that is hidden from the main roads. A kind of asylum exists for previously dangerous or deprived elephants in captivity, now living the rest of their lives here in the semi-wild. Driving past the perimeter fences, an awareness that huge animals are nearby and unseen evokes comparisons to Jurassic Park, but with a therapeutic mission. The Elephant Sanctuary, a private nonprofit organization in Hohenwald, Tenn., spans 2,700 acres of forests and spring-fed ponds.
This is a last refuge for elephants broken by humans, and they are here to heal. But doing so requires the elephants' ultimate act of trust in humans.
On a recent visit, ABC News correspondent Elizabeth Vargas was chaperoned inside the gates to discover an intimate world.
"She has her ears out so she's checking it out. And since she's the matriarch it's her job to make sure that everything is safe. It's a sign of trust and intimacy," said Carol Buckley as she approached an elephant named Shirley.
Buckley and Scott Blais, co-founders of The Elephant Sanctuary, establish trust with the animals, guided in part by the new theory that if humans and elephants can both suffer from Post-Traumatic Stress Disorder, maybe we can also share the hope for recovery.
"What we have learned, and what we have seen, without a doubt, they are experiencing some level of Post-Traumatic Stress Disorder," said Blais.
Creating a safe environment is vital to the progress made at the sanctuary, where 17 former circus and zoo elephants walk without chains or threat of abuse.
Applying techniques used to treat humans suffering from PTSD, Buckley and Blais research how these elephants have been stressed in the past, their responses, and tailor the sanctuary's programs to help each one.
Elephants once dangerous and isolated in captivity discover how to play again with new friends.
"They operate on a much deeper plane than we do, and you can't help but be fascinated with that," said Blais.
It's a sentiment Buckley shares.
"I think that's what happens with people who are around elephants. There's some profound connection that is made that is deeper than we have ever experienced before," she said.