- [Isabella] Martha's Vineyard is known as a salty escape, a place where celebrities and New Englanders alike can leave their mainland worries behind.

It has a culture and a lingo of its own.

- The little frogs called spring peepers are on the vineyard called pinkletinks, or tupelo trees are called beetlebung trees.

- [Isabella] But unbeknown to the average vacationer, Martha's Vineyard is home to another language.

- Cranberry.

Swordfish.

Swordfish.

- [Isabella] One not spoken, but signed.

- I can't hear, damn it.

- [Isabella] Joan Poole Nash grew up in the vineyard and learned sign language at age seven.

- I learned sign language from my great-grandmother and it became our private language between the two of us.

I had no idea where the sign language had come from or why she used it.

- [Isabella] Her best guess was that they were Native American signs from the back of the Boy Scout manual.

But when she went on to study American Sign Language or ASL in college, it dawned on her that these signs were special.

- There's a sign that no one had another sign for, which was twins, and this was a sign for twins, two of them rolling around inside.

- [Isabella] These were the days when many academics didn't believe sign language was a real language, so evidence of signs growing and changing could be groundbreaking.

- Everybody got super excited and we went over to the vineyard and interviewed all my relatives that we thought had been exposed to the sign language.

- [Isabella] Relatives like Eric Caudle.

- That was diamonds.

That was clubs.

That was hearts.

That was spades.

- [Isabella] Who remembered deaf neighbors playing cards in town.

- They could concentrate, you know, no distraction.

- We ended up collecting about 300 signs.

- [Isabella] Signs like scallops, codfish, and New Bedford.

The historic whaling port sign translates to... - Smells bad over there.

- [Isabella] But how did an early American sign language spring up in Martha's Vineyard?

We met Bow Van Riper, a historian at the Martha's Vineyard Museum, to learn more.

Today he's taking us to the home of Martha's Vineyard sign language, Chilmark.

- Maybe one in 150 people in Chilmark as opposed to one in, say, 1,200 people in an average village on the mainland were deaf.

Martha's Vineyard sign language developed in Chilmark into essentially a second language alongside spoken English.

- [Isabella] Our first stop, the Chilmark Town Church.

- Jared Mayhew, who was one of the biggest landowners and sheep farmers in town, was deaf.

But his wife, Lottie, short for Jerusha, could hear and she'd sign the sermons to him.

- [Isabella] We also went to the home of Katie West.

- She always told the story that at the age of three or four, she was struck by lightning and lost her hearing as a result.

- [Isabella] And visited the old town hall.

- Here in Chilmark, deafness was just another way of being human.

- What's our best guess as to where this gene for deafness came from?

- The first deaf person we know of who lived on the vineyard was a guy named Jonathan Lombard, who came to the island in the very early 1700s from an area of southeastern England called The Weald.

Martha's Vineyard in the 1700s and really as late as the middle of the 1800s was quite isolated from the rest of New England.

Most people, when they got married, married somebody else from Chilmark.

This meant that the likelihood of them marrying somebody who also had the gene, and thus both of them passing it on to their kids, was significantly higher.

- Chilmark became a deaf enclave, attracting the interest of one of the most famous inventors of the time.

What brought Alexander Graham Bell to the island?

- Alexander Graham Bell, having long been interested in deafness, his wife, for example, was deaf, was living at a time when the causes of deafness weren't yet well-understood.

Because he suspected deafness was hereditary, an area like Martha's Vineyard might shed some light on what was going on.

And here's Bell's name and address.

- [Isabella] Alexander Graham Bell painstakingly mapped Chilmark's family trees.

Today, however, his motivations for research are controversial in the deaf community.

- Bell was deeply opposed to sign language and was a proponent of what was known in the day as eugenics, the control of human reproduction in order to produce a better human race.

He discouraged the deaf people he interacted with from marrying other deaf people.

- [Isabella] Bell was never able to figure out the pattern of how deafness is inherited, but today, academics use his old records to find new answers.

Justin Power is a researcher in linguistics at the University of Texas, Austin.

He has a new theory about how and when the sign language began.

- Humans are homo symbolicus.

We're the symbol users.

If you have a group of deaf individuals who are regularly interacting with one another, they will try to communicate with one another.

In a short span of time, 1785 onwards, two families had a relatively lot of deaf children, and that's where we hypothesized that the Martha's Vineyard signing community actually began.

- [Isabella] A community of hearing and deaf, both using signs.

Power estimates that Martha's Vineyard sign language developed in isolation for about 40 years, but everything changed when the American School for the Deaf was established in nearby Hartford, Connecticut.

Here, ASL would develop.

- In 1825, the first three deaf individuals from Martha's Vineyard went away to Hartford to study at the American School for the Deaf.

- [Isabella] Today's historians have new ideas about the similarities between Martha's Vineyard sign language and ASL.

The traditional view says that signs from Martha's Vineyard were adopted by ASL, but Justin Power believes that it was mostly the other way around.

- So you can imagine that the deaf individuals would've shifted eventually to use more American sign language.

(ferry horn honking) - [Isabella] It was the start of deaf education in America, but it was the beginning of the end for Martha's Vineyard sign language.

- So the opening of the American School for the Deaf coincides with the beginnings of reliable steam-powered ferry service to the island.

- How did that affect the number of deaf people born?

- The marriage pool broadens, and although there are still deaf people born on the island, it drops significantly, - Lots and lots of words.

- [Isabella] After her landmark research, Joan Poole Nash went on to have a decades-long career teaching the deaf.

Before we parted, she had a lesson to share.

- So the only thing that's gonna move is your thumb.

You need to go up higher.

Yeah.

And now flick your thumb.

Yeah.

Cranberry.

As far as American sign language goes, they don't have a sign for cranberry.

So I make it my job to teach everyone so that sign doesn't disappear.

(uplifting music) - Finally tonight, as beach season begins,