[bright music] - Who is that?

"Think me there."

Okay, that is you.

"Gorilla, animal, Koko-love."

Okay, that's very good, that is you.

You are a lovely animal.

- [Martin] When Penny Patterson and Koko, a western lowland gorilla, met nearly 30 years ago, neither had any idea they would become friends for life.

- [Penny] Mm, very nice.

- [Martin] In the long history of human-animal relationships, their story is one of the most fascinating.

It is the true tale of a young woman and a gentle giant walking hand in hand into a whole new world of understanding.

They couldn't have known that their intimate friendship would shatter century-old stereotypes and change forever our outlook of both gorillas and ourselves.

Penny describes her friend with gentle honesty and affection.

- Koko's about five feet tall.

She weighs roughly 300 pounds, little heavy for a female.

The average is 250.

She's a big female gorilla.

Koko has a very strong sense of self.

She feels she's important, she's got a strong ego.

She's playful, can be very silly.

A quick spin, a quick, a really quick spin and then once you're good and dizzy, send you off.

She's got a good sense of humor.

Oh no, a monster, a monster coming to get the alligator [laughs].

She can be very stubborn, very willful.

Finished, you are not finished, you are not.

You are not finished.

You didn't do the work I asked.

Please pick those up, Koko, you are very good at that.

Please pick 'em up.

- [Martin] Their relationship is like no other.

Penny and Koko are the first human and gorilla to share a common language.

Penny taught Koko to speak sign language.

- Play with them after you help, okay?

No, no, not fake, no, what?

- [Martin] Their exchanges, their conversations were enchanting and quickly revealed the power language has to build a bridge between our species.

- Then you go and bring those papers.

[gentle music] - What, good, you did, he was visiting you and bit?

When I look into Koko's eyes and other people have said this, that they have changed forever.

That there's an exchange of intellect and emotion that we get with another person.

Koko's looking, peering into your eyes and questioning you and asking you and getting information from you, drawing you out.

She can do that because she has sign language.

- [Martin] By teaching Koko a language humans can understand, Penny armed Koko with a powerful tool that allowed her to speak as an ambassador on behalf of her endangered species.

Astonishingly, Koko is willing to provide us a window into her life, her mind and her heart.

Who could have imagined that a gorilla could fall in love with a kitten, search for a mate and yearn to be a mother?

She has challenged us to acknowledge that we share this world with other intelligent animals.

- [Penny] There is very little difference.

Genetically, it's what, 2%?

Something like that.

When I tell people that we have the same number of hairs per square inches as great apes, they go, "No, that's impossible."

Or that we have the same blood types.

"Oh, come on, you know, that's not right," but it's all true.

[bright music] [dramatic music] [dramatic music continues] [dramatic music continues] [bright music] [bright music continues] - [Martin] Koko, whose Japanese name Hanabi-Ko means Fireworks Child, was born on the 4th of July in 1971 at the San Francisco Zoo.

Koko's first few months of life were not easy.

She became very ill and had to be cared for in the zoo's nursery.

As Koko grew stronger, Penny considered a revolutionary idea.

The young doctoral student in the psychology department at Stanford University wanted to work with Koko.

She proposed that a gorilla could learn to speak with humans using sign language.

- [Penny] My initial expectation was that I would work with her about four years and then I would get my degree and move on.

After the first few evenings trying to leave her, I couldn't, I couldn't put her down, so I ended up staying with her until she was asleep.

- Koko won me over right away and within a few weeks of working with her, I could never really want to separate from her.

You'd have to pull us apart.

- [Martin] Dr. Ron Cohn has been the cameraman behind the scenes for nearly 30 years.

He helped Penny raise Koko while doing post-doctoral work at Stanford.

All the while, he's kept his cameras rolling.

His tireless work behind the lens documents the incredible journey of a gorilla growing up in a human family and learning to talk.

[gentle music] [birds chirping] Encouraged by the little gorilla's eagerness, Penny took the first steps into a new frontier of inter-species communication.

She taught Koko her first words, "Drink," "Eat," and "More."

Penny would make the sign for "Drink" and then help Koko do the same.

[bright music continues] The signs for "Eat" and "More" came next.

If you watch Koko closely, she's learning to put her fingertips to her mouth to sign eat and her fingertips together to sign more.

[bright music continues] [Penny laughing] [bright music continues] - At first, I think it was almost like, oh, if I do this, then they give me stuff.

That was what she got out of it initially.

[bright music continues] - [Martin] Learning vocabulary was a beginning, but in order to have a conversation, Koko had to learn how to use her new language.

[bright music continues] Koko approved an adept student.

Everyone was amazed at how well the little gorilla was catching on.

- I think within two weeks, Koko was using sign language.

I couldn't believe it.

- [Martin] Over the next months and years, Koko's vocabulary grew to over 200 signs.

Koko was making unprecedented strides and national news.

Penny was happy to report the little five-year-old could not only talk, but was redefining our concept of gorilla intelligence.

- Koko has performed consistently at a level about a year behind a child her age, so that she, when you calculate an IQ, which is a ratio, comes at about 85 and 100 is normal, quote normal [laughs].

What I didn't know then was that gorillas already have their own gestural system, that I was just building on or discovering, you know, depending on the way you looked at it.

- [Martin] Only recently, Penny and an associate, Joanne Tanner, discovered that gorillas use a system of gestures to communicate.

Joanne has identified dozens of signs as part of their natural gestural language.

The discovery of this innate gorilla ability helped explain Koko's remarkable affinity for a human sign language.

Using an elaborate verbal language is something unique to humans.

We are the only primate with vocal cords developed enough for complex speech.

- Oh, the dog got old, so he.

- [Martin] Today these third graders are learning a gestural language.

DeeAnn Draper, one of Koko's caregivers, is teaching them American Sign Language or ASL, the same nonverbal communication system Koko was taught.

- Gorilla, right, you guys are great.

If she wants to tell you yes, she usually says good, good.

Another one of her signs is chase, chase, good.

This finger, candy.

- [Martin] Koko has created her own version of sign language called Gorilla Sign Language or GSL.

She has adapted some signs to fit her large hands and body.

- You can see this is a imprint here of Koko's father's hand, but his thumb is only about as big as mine.

When you try to make some of the signs in American Sign Language with a teeny little thumb, it's impossible.

This is a K and the way people do it is, this is Koko.

She usually doesn't make the K because there's that thumb thing again, right?

She can't reach this one too well, so she usually just does this, Koko-love.

There you go, Koko-love.

Visits, okay, visits.

You guys are very nice visits.

- [Class] Nut sandwich, nut sandwich.

- When Koko does hurry, she doesn't just go hurry all the time.

She uses different modulations.

She uses hurry or hurry or hurry or hurry!

- [Class] Hurry!

- [Martin] What had gone unrecognized is that humans and gorillas share a fundamental ability to learn language.

- Just like you can't teach language to a child, they learn it, it's that same distinction.

It's not training.

It's exposing her to something and letting the wiring, the genetic makeup, do what it would normally do.

- [Class] We love you, Koko.

[bright music] [bright music continues] - [Martin] One day in September, 1976, Penny told Koko a surprise was on the way.

A baby gorilla was joining the family.

[bright music continues] Penny and Ron had heard of a young male named Michael who needed a home.

They jumped at the opportunity to add him to the family.

The goal was to provide not only a companion for Koko, but also a potential future mate.

- When we first got Michael, I remember opening the cage 'cause I wasn't afraid of gorillas and letting him out and you know, he ran right to me and hugged me and sunk his teeth into my shoulder.

You know, since then he was very good with me.

- [Martin] When Michael and Koko met, Koko was disappointed.

She signed "Wrong, old," she'd been told he was a baby.

Michael was already three and a half.

Their first few weeks together were a bit difficult.

Much like an only child being introduced to a new sibling, Koko wasn't ready to share her world.

Ultimately the youngsters were left to work it out and their struggles turned into a raucous wrestling match.

[bright music continues] [gorillas thumping] They eventually settled into a comfortable relationship.

When Michael wasn't pestering Koko, they often engaged in a playful game Koko called "Quiet Chase," "Hide and Seek."

[bright music continues] [bright music continues] [bright music continues] Penny soon enrolled Michael in the sign language preschool and after just 12 months he had learned more than 20 signs.

- Here, here, Mike, your banana, do you wanna give?

- [Martin] Over the next three years, Koko and Michael doubled in size and Penny knew it was time for a more spacious and permanent home.

In 1979, Penny and Ron moved their gorilla family from Stanford University into the nearby Santa Cruz mountains.

[bright music] The six and a half acre site became the new home of the Gorilla Foundation, which Penny and Ron had established in 1976.

[bright music continues] The secluded woods and nearby orchard provided the gorillas with a quiet sanctuary.

They now had a small buffer from the outside world.

Here, Penny and Ron could live and work right on the property and there was plenty of room for spacious play yards to be built for Koko and Michael.

By now, an endeavor expected the last only four years had gone on for nearly 10.

During this time, the bond between Koko and Penny had matured into an intimate friendship.

Observing their interactions reveals a relationship based on respect, trust, and love.

- You wanna tell me about that, what are you doing?

Oh, you don't, all right, it's private.

I won't bother you then.

You paint how you feel.

"I feel nice, you there," okay.

- [Martin] Koko was now fluent in signing.

She had been given a voice and used it freely to convey her wants and her needs.

- Why would I owe you a nut?

Because you're good, oh.

Chase in, chase where?

"You toilet do go."

Do you sleep?

Okay, [laughs] it's fine.

[bright music] - The obvious emotions that Koko showed me in the beginning were crying, distress, laughing.

Oh, tickling her is so funny.

You gorilla, tickle, catch, okay.

All the subtle emotions are there, the guilt.

What happened?

Broke bad, hungry bad.

Oh, honey, Koko-love.

Oh, all right, we'll make up.

[kisses] I give you kiss, thank you.

At one point Ron was filming and I was doing something else and she's eating paper.

She's always trying to steal little bites and looking like, do they know what I'm doing?

I know I'm doing something that is bad.

No, that's not the way to play with it.

- [Martin] Koko was proving daily that she experienced and understood complex emotions and she had no trouble making her feelings known.

- There were times like raising children where they drive you nuts and you do shout at 'em.

That's it!

Mostly, I think what you're seeing is that she fascinated me.

If she had been my human child, I wouldn't have had the same patience.

Not to say that it wasn't frustrating at times, but that it was tempered by this just fascination.

What are we doing [laughs]?

[bright music] [bright music continues] - [Martin] Koko has always enjoyed looking through books and magazines.

She especially likes the pictures and often signs to herself about them.

[bright music continues] One of her favorite books is "The Three Little Kittens."

Koko would ask Penny to read it again and again.

- "Lost their mittens and they began to cry."

- [Martin] There was something in the story that seemed to touch Koko.

- Right, "And cried and cried."

- [Martin] Eventually Koko asked Penny for a real kitten of her own.

- How do you feel about kitties?

"Cat, gorilla, have visit, Koko-love," good.

- [Martin] So Penny did what her friend asked and found a tiny baby cat for the 300 pound gorilla.

[bright music] The story of Koko's relationship with her first kitten became an unexpected means for us to understand the depth of gorilla emotion.

When this photograph taken by Ron made the cover of "National Geographic Magazine" and when the book and video about "Koko's Kitten" were shared with millions, the world was able to see gorillas in a whole new light.

[All Ball meowing] - [Penny] Koko has impacted people in a sort of at a mass level because of that image.

The reason that it's so it stands out in people's memories is because there's an emotional surprise there.

There's a giant gorilla with a tiny, tiny, tiny helpless kitten and being gentle and loving toward that kitten.

- [Martin] Koko rhymed a name for her new kitten.

She called him All Ball because to her the cat looked like a little ball.

Koko adored All Ball and they spent countless hours playing together.

And yet it was by loving the little tailless kitten that Koko learned one of life's hardest lessons.

[somber music] One evening All Ball was tragically killed on a nearby logging road.

Koko was heartbroken.

- [Penny] Koko, All Ball was hit by a car.

I went in right away and I said, "Koko, something's happened "to your kitty and he won't be here anymore.

"You know, the cat has died."

[somber music continues] - [Martin] Penny stayed with Koko to comfort her.

[somber music continues] And later privately Koko expressed her grief.

[somber music continues] [Koko hooting] Although Koko had experienced love and loss, Penny discovered that in time her wounds could heal.

Soon, boxes and baskets of kittens began to arrive.

The world was trying to help Koko find a new feline friend.

- All the little troubles, all the little troubles, all the little troubles, there, you have them all!

- [Martin] Koko loved playing with all of them, but finally chose another tailless kitten she named Smokey.

Today, Koko and Smokey remain two of the world's most extraordinary friends.

[gentle music] [bright music] Over the years, Koko has become world famous.

Celebrities and journalists have found their way to Koko's secluded home in the hills of northern California.

- Aw.

[bright music continues] - You wanna see that, really?

Well, okay.

[group laughing] Put 'em on the other way.

- [Martin] On occasion, special friends drop by and Koko indulges her audience with a little showing off.

- [Spectator] Hey, that's cool.

[playful music] [spectators laughing] Ah I like that, that's great, Koko.

[playful music continues] - [Penny] Hey, Kok, you wanna trade?

Trade the look glasses for something I have in my pocket?

[playful music continues] Oh, look, let's makes a deal.

Oh, you're pretty good about this, ah well, very nice.

- [Martin] Koko met her youngest visitor even before he was born.

This infant's mom, Meg, was one of Koko's caregivers and had visited Koko while pregnant.

- [Meg] It's the baby Koko, remember the baby?

[gentle music] Stomach, right, you're so smart.

- [Penny] Yes.

- [Meg] What do you think, Koki, do you want to have a baby, Koki?

[gentle music continues] - [Martin] Gorillas reached puberty at about age 10 and begin to express an interest in mating and having babies.

Koko and Michael were no different.

[bright music] - Okay, look, a surprise.

- [Martin] Without other gorilla role models, it was up to Penny to help Koko understand gorilla reproduction.

- It had a baby, she had a baby.

I knew Koko wanted a baby because the first time I saw it, she said, "Me, that," to the gorilla on the television screen that was holding a baby.

Very definitely pointing to the baby in the picture.

Also, the way that she treats her gorilla dolls.

Not her human dolls, not her troll dolls, not any other doll but her gorilla dolls, she takes their hands and makes them sign things.

She teaches her baby "Eat," "Drink," and "More," the first three signs she was taught as a baby.

You love, drink, where does the baby drink?

"Drink," the baby signs she's gotta drink with the mouth.

"Drink, mouth," she's had the baby answer, the baby said, "Drink, mouth," that's right.

Most important a baby would make Koko happy and what we wanna see is cultural transmission.

That's the term for it, is that she would actually teach her offspring in the way that we taught her.

- [Martin] That Koko might teach her baby to sign is an exciting possibility.

She has learned over 1,000 words and uses a vocabulary of 500 regularly.

- All right, what did you make here, "Hat, fake?"

- [Martin] Koko has mastered the subtleties of sign language so well that literal translations don't always capture the complexity of her thoughts.

Throughout the decades, Koko's teachers have used both sign language and spoken English.

The fact that Koko understands English makes her seem especially human-like.

- One more and then you turn it off, okay, good.

Let me see your tongue.

That looks fine, okay.

- [Martin] Koko has truly made sign language her own by inventing or creating totally new signs.

Dina, the foundation's lead caregiver, converses with Koko on a daily basis.

- We say things in English and if we don't give her a sign for it, she has no way of telling us that that's what she wants.

Browse is like the lettuce and greens that we give her between meals and we didn't have a sign for it and Koko started doing this and at first people didn't know what it was, and eventually it became clear that she was asking for browse and it's at the eyebrow.

So she was using the sound to come up with a sign, browse.

- [Martin] Koko, like any of us, can be frustrated when others don't understand what she's trying to say.

- I don't understand, oh, sorry.

It's bad that I don't understand.

I'm a little dense, honey, shame.

It's a shame that I don't understand what you're trying to tell me.

- [Martin] By putting two descriptive words together, Koko invents compound words that better communicate what she's trying to say.

- Hair, yes, this is for your hair.

"Scratch, comb," it's a scratch comb.

That's an interesting word for a brush.

Nice, I need help with my hair today.

Yeah, this side too.

She'll create a word if there isn't one, eye hat for a mask, a finger bracelet instead of ring.

- [Martin] Almost every conversation or sign Koko has made in the presence of Penny or a caregiver has been dutifully entered into a daily journal.

These records are being studied to better understand the structure and meaning of Koko's signing.

- What I'm trying to do with this database that I'm working with right now is categorize the words that they use.

Is it a modifier word?

Is it a social word or an emotional expressive word?

And they talk about everything.

They aren't just asking for food, they aren't asking for rewards.

They're talking about things, they're commenting on things.

They're gonna show people how well they have this language in hand.

- [Martin] Over the years, Penny has enjoyed watching Michael and Koko's individual personalities emerge.

- [Penny] Michael is a totally different personality than Koko, Koko tends to be chatty, Michael is a man of few words, but what he does say is very to the point and on target.

- [Martin] Since arriving at the foundation, he has developed a vocabulary of over 500 signs.

As he matured, Michael developed a distinctive crest of silver hair across his back and shoulders.

He's the alpha or dominant male, a 450 pounds silverback, three times as strong as an average man.

He is self-reliant and has an active, inventive imagination.

[energetic music] An astounding dimension of Michael's character was revealed when he recounted a terrifying memory from his life as a baby in Africa.

[vehicle droning] Every day in Africa, logging and poaching threatened gorilla survival.

It seems likely that during a poaching raid, Michael witnessed his mother being murdered and butchered for meat.

[ominous music] [gun firing] It is with shocking regularity that entire family groups are killed for food.

This infant chimpanzee was spared, but his parents were not.

[somber music continues] When asked about his mother, Michael told Penny a very disturbing story.

He signed, "Noise, trouble, and cut neck."

Penny believes he was describing how he became a captive gorilla.

[somber music continues] The Gorilla Foundation hopes that by sharing Michael's story and by raising awareness about how thousands of great apes are hunted and killed each year, the tragedy that made Michael an orphan might stop.

[somber music continues] There is no way to know the exact impact this memory has had on Michael, but Penny believes it has shaped his personality.

- [Penny] Michael is just a totally different individual.

He is very, very sensitive, very artistic.

He is fond of classical music and he paints beautifully.

- [Martin] Since they were young, both Michael and Koko were surprisingly skillful at expressing themselves through painting.

One of Michael's first paintings was of his favorite dog, Apple, who Michael loved to play chase with.

Michael painted his faithful friend from memory, entitled it "Apple Chase."

From the many colors he was offered, Michael deliberately chose only black and white to create this remarkable impression of Apple and the sense of the chase.

[gentle music] Koko and Michael surprised the world with their artistic ability.

The fact that they select specific colors from a full palette and paint with such purpose and intent is no less than amazing.

- [Penny] Excellent, excellent.

[gentle music continues] [gentle music continues] - [Martin] When the gorillas' artwork goes on display, Penny and Ron decide which pieces to send to the gallery.

- When I got to see Koko and Michael's pictures in a portfolio, I was really excited about what I was seeing and the idea of giving them an art show was really exciting.

Michael's art is very emotional, it's full of color.

It fills up the page.

It has a lot of activity, a lot of action.

- [Martin] Michael's paintings are often about how he feels.

He paints his emotions with intensity, [gentle music] and his still lifes with surprising finesse.

[gentle music continues] "Stink," in GSL means flower.

Michael painted a large bouquet and entitled his finished work, "Stink Gorilla More."

- This painting, "Stink Gorilla More" looks to me like a vibrant spring bouquet of flowers.

You can see where he was lighter with the brush, maybe had some heaviness in certain areas.

It's almost like music in the same way you'd vary things.

- [Martin] But Koko and Michael aren't the only ones with a creative eye.

Ron's photographs have given the world a powerful insight into these magnificent beings.

- My interest in taking pictures of the gorillas is as great as it was 27 years ago.

There is a lot I need for people to see about them, and I'm flattered that the gallery wanted to put some photos in here.

And it also helps for people to relate to the artwork that the gorillas do, especially children.

They can see what Koko's and Michael's personality is like.

There's a black and white photograph of Michael.

He looks half human.

And what's eye-catching about that is that people see human-like qualities in an animal.

[gentle music] - [Martin] Michael's life story is a compelling one.

Since his arrival at the foundation as a toddler, he has offered Koko companionship, but the question remains as an adult, would he become her mate?

[gentle music continues] [birds chirping] Koko and Michael's day at the Gorilla Foundation begins with one of their favorite things, food.

DeeAnn, one of the gorilla's caregivers, arrives each morning with boxes of fresh organic fruit and vegetables donated from a nearby market.

A delicious breakfast, lunch, dinner, and several snacks are specially prepared to include lots of the gorilla's' personal favorites.

- We consider and the gorillas consider their food to be the highlight of their day.

This is the most important thing to them.

[bright music] She has her favorites, she loves green beans and corn, Brussels sprouts, a few things like that.

[bright music continues] Koko gets somewhere between 10 and 12 pounds a day.

[bright music continues] Perfect.

[energetic music] So we're done.

- [Martin] Gorillas sleep about 12 to 14 hours a night, and by 8:30, Ron and Penny personally deliver breakfast with a morning wake up call.

- Hello, cutie pie, where are you?

Okay, little bean, enjoy.

[bright music continues] [bright music continues] [bright music continues] [bright music continues] Okay, we'll go outside.

[bright music continues] [upbeat music] [birds chirping] - [Martin] Koko and Michael have spent many years together.

They have developed a strong friendship, but Koko doesn't seem interested in mating.

Penny has discovered why.

- [Penny] At that time we didn't understand that when gorillas are raised together, there is a taboo against mating just as there is with human.

- [Martin] Koko considered Michael her kid brother.

The two had developed a sibling bond, not a mating bond.

Koko continued to express her powerful instinct to be a mother.

She yearned for a baby of her own.

- Koko, would you like to?

- [Martin] So Penny took on the role of matchmaker and went in search of a boyfriend for Koko.

- Do you know how to do that?

- [Martin] With so few males accessible, the search narrowed rapidly.

Penny collected videotape of the available bachelors, and Koko began an unprecedented journey into the world of video dating.

- Okay, you watch the gorilla.

Do you like his looks?

When Koko was looking at the videos to pick her potential mate.

Koko-love.

It was a thumbs up, thumbs down reaction.

Oops, she just turned the thing off [laughs].

There he is.

If she liked the gorilla, she would kiss the screen.

[Koko kissing] You kiss him, do you like him?

Good, do you like him to visit?

- [Martin] And she outright rejected others.

- "Gorilla, no, away," [laughs].

- [Martin] Then along came in Ndume.

[Koko growling] - Burr, is that what you were telling me, "Bring," do you like Ndume on TV?

- [Martin] Ndume, which means "male" in Swahili, was the 10-year-old bachelor who caught Koko's eye.

[Koko kissing] - Oh my goodness, a big kiss.

Do you like Ndume in person, do you like him to visit?

[bright music] - [Martin] Local press gathered at the Gorilla Foundation to cover the arrival of Koko's new beau.

Penny had successfully relocated in Ndume from the Cincinnati Zoo.

As ever, Ron was documenting this important moment.

Ndume's first steps into the play yard marked the beginning of his new life at the foundation.

He had no idea he was joining a famous family of talking gorillas.

[birds chirping] Ndume's secret admirer waited in the wings while he settled in.

[birds chirping] It didn't take long for Koko to ask to meet in Ndume face-to-face.

Normal protocol calls for the gorillas to play in adjacent yards for a few weeks, giving them time to get acquainted.

But Koko quickly confided in Penny that she wanted to meet Ndume now.

- [Penny] "Visit do there, good."

How do you know to go in there, huh?

How do you know, how do you know that?

"Nice, good, Koko-love, hurry, good, hurry, have nice."

Oh, you're going to be nice?

"Koko-love, good," okay, you're going to be nice, huh?

- [Martin] Penny honored her request and allowed Koko to enter Ndume's yard right away.

[Koko purring] - Oh, good purr.

[suspenseful music] - [Martin] The question of whether they would get along would soon be answered.

Would Ndume, half Koko's size and 10 years younger, be nervous on Koko's home turf?

[suspenseful music continues] Would there be dominance displays or mating invitations?

Whatever the message is, we humans are just beginning to understand.

[playful music] [playful music continues] [playful music continues] [playful music continues] But finally, from Koko, an invitation to play.

[playful music continues] An invitation accepted and returned.

[playful music continues] [playful music continues] Penny watched as the days and weeks passed.

[playful music continues] [log thumping] Nature took its own course and the relationship between Koko and Ndume began to grow.

[playful music continues] [playful music continues] [metal thumping] It could be months, even years before Penny would know if Koko's instincts were right.

Was in Ndume the one who would help her build a family of her own?

[gentle music] [birds chirping] In an adjacent play yard with his typical independence and good humor, Michael adapted to the life of a bachelor.

Over the next few years, Penny intensified her search for a female gorilla in need of a home, this time a mate for Michael.

Meanwhile, the trio has spent their days doing what gorillas enjoy most, playing, relaxing, and eating.

[bright music] [bright music continues] While Koko's biological clock ticked, she and Ndume engaged in gorilla play.

They spent years together teasing and roughhousing.

And although the rules to gorilla games like "Tug-of-War" are simple.

- [Ron] I agree.

- [Martin] The guidelines for successful gorilla mating are uniquely complex.

After years of courting and flirting, why had Koko and in Ndume not yet mated?

Penny believed that Koko might not be at ease in a company of two adult male gorillas.

- In the jungle, it's a male and up to 12 or 15 females, never one male, one female, never, ever.

And while we like that set up, a gorilla does not.

A female gorilla is very uncomfortable with that, very insecure, and this is really important.

She needs that social support.

If she had that family, I would sort of fade in importance, and I should.

You could climb up.

She could well outlive me.

Gorillas' record is 54, she's 27.

So that's what I'm striving for.

So that if something happens to her human family, she has the more important gorilla family.

This is your boyfriend, right?

- [Martin] To reinforce the mating bond between Koko and Ndume, Penny thought a pep talk might help.

- [Penny] He could help you make babies.

You gotta get your nerve up though.

You gotta go talk to him about it.

Hmm-hmm, this is the man, right here.

[Koko purring] [gentle music] - [Martin] Without the support of a typical family group, Koko is less likely to conceive.

It's been eight years since Ndume arrived, and still there is no baby.

- Koko had nothing to do with being born in a zoo.

She had nothing to do with being made a subject of a, quote, experiment, that wasn't her choice.

And I wanna do the best I can for her.

So, and for Michael and for Ndume, and for as many other gorillas as need a safe place, a sanctuary.

- [Martin] In Hawaii, the Maui Land and Pineapple Company has donated 70 acres for a tropical preserve that will provide the gorillas with greater freedom.

Penny hopes a nearby interpretive center will inspire visitors to conserve habitats for gorillas and for all the world's species.

[bright music] Over the years, Penny's passion for Project Koko has never wavered.

- Okay, okay.

- [Ron] Their relationship is magic.

It was magic from the beginning.

- All right, oh, we are heavy, but we are having a hug time.

- Her ability to work with animals is unique.

I've never known anyone who could do what she does.

- Thank you, check that out.

- [Martin] Along the way, Penny's scientific study turned into something far more important.

She not only cares for the wellbeing of her gorilla family, but she is also working for the survival of their entire species.

Koko, Michael and Ndume have become the heart and soul of her world.

[bright music] - People ask, "Do you have any kids?"

And I say, "No, I have three gorillas."

They think that I'm insulting my children, but those, my children are gorillas, I'm sorry.

And that's probably the way I would've written it if I had complete control over the outcome of my life.

- [Martin] Koko's life with humans has afforded us an opportunity to look into the eyes of another animal and recognize our kinship.

[gentle music] - [Ron] I think people conceptually find it uncomfortable, but when they see Koko, there's something different.

And their conscious and subconscious have to work it out.

- [Penny] They're us, we are the naked apes.

We are apes, they are us, we are them.

There is very little difference.

It's just hard for us to accept because they look so different on the surface, but it's just a surface thing.

They're like us inside.

[bright music continues] - [Martin] In Penny's search for a deeper understanding of gorilla intelligence, she found not only that Koko could learn, but that Koko could love.

And through their intimate friendship, their conversations, they were able to share with us a rare phenomenon, the opportunity to meet mind to mind with another talking animal.

- "Play, there."

Oh, these guys, play with my earrings.

This trouble earrings, just because.

- [Martin] As for Koko's future, there are still many chapters left unwritten.

[bright music] But from her years of conversing with us, we have at least learned that what it means to be a gorilla is far richer and more complex than we could have ever imagined.

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