The "gestural" origin of language in humans is supported by our research, which means that we most likely used gestures to communicate before we developed the neurological wiring and anatomy to produce speech. Gorillas have a complex communication system of their own involving gestures, postures, facial expression and vocalizations (if you watch them closely) and we have merely extended their vocabulary to include shared aspects of our gestural language so that they can communicate with humans (ie, American Sign Language).
A cognitive basis for language acquisition is also supported, which means that being able to use language to communicate does not depend on having a species specific "language acquisition device" but rather can be learned and used creatively if there is sufficient intelligence/awareness. This is why sign language can be used by gorillas and why they can comprehend spoken language, even though they are not genetically pre-disposed for speech (they can and do make meaningful vocalizations, but their vocal cords and surrounding anatomy do not allow them to produce human speech).
All of the non-human great apes (ie, gorillas, chimpanzees, orangutans, and bonobos) have the capacity for all the essential features of language, including the use of basic grammar without being specifically taught it - and the invention of new words and phrases.*
* There is also a cultural component to language acquisition by great apes, as Koko and Michael may not have developed such high levels of proficiency with sign language if they had not been motivated by the correspondingly high levels of care, respect and expectation to succeed given to them by Dr. Penny Patterson and staff. They were essentially accepted into the human family as equals, and the degree to which this made a difference in their language acquisition would make an interesting, but difficult to conduct, study.
Similarity to Humans
Gorillas are essentially similar to the human great ape- intellectually (Koko tested in the 80's and 90's for IQ), emotionally (Koko, Michael and Ndume have exhibited all of the complex emotions we do, and exhibit empathy with other creatures). Their ability to feel pleasure and pain (both physical and emotional) — which they can communicate specifically to us using sign language — means it is unethical to intentionally cause them to suffer. In particular, it is unethical for humans to hunt gorillas (and other great apes) and eat them — which is exactly what is happening in Africa, fueled by Western logging and mining companies who open up their habitats to hunters and create a demand for "bushmeat." Knowing what we now know about the other great apes and knowing that we are also a great ape, this is akin to cannibalism.
Gentle, Meditative Nature
Gorillas live in harmony with nature, and being exposed to their gentle, meditative nature (even through video) can and does have a positive influence on humans — helping us get in touch with the simpler aspects of our intrinsic nature. Autistic individuals have a special affinity for gorillas and have been helped to overcome aspects of their disability through relating to gorillas.
Koko, and her ability to communicate and empathize with humans and other animals (eg, kittens) is having a profound effect on education. Teachers around the world have communicated to the Gorilla Foundation that, because of books such as Koko's Kitten and documentaries such as "A Conversation with Koko," their students have been motivated to learn, to read, to write, to do science projects, to care about conservation, and even to enter socially and environmentally conscientious careers. Learning-disabled students, who have difficulty with basic reading and writing, have been especially inspired to ask to do more reading and writing after being exposed to Koko. The potential benefit to education has been largely untapped, and the Gorilla Foundation is beginning to work with educators to reap the benefits to mankind.
The success we've had in teaching sign language to gorillas offers promise to using sign language as a tool to improve communication with: a) babies, b) the disabled, c) people who speak different languages to communicate with each other in a more universally understood system. Sign languages are more iconic than spoken languages, and visual languages can add a new form of stimulation to the developing brain and engage the mind in new and creative ways. (For example, a Spanish teacher who incorporated sign language into his classroom, found that students learn and retain Spanish better. When he incorporated a study of Project Koko to his curriculum, he was able to more easily motivate the students to learn sign language and other subjects.)
Stewards of the Planet
There is much more to learn through interspecies communication about the origins of language, intelligence and the role of species biodiversity on this planet. Knowing what we know about the great apes through individuals like Koko makes clear our moral responsibility as stewards of the planet. But we will never be able to learn these lessons fully if we allow the great apes to be driven (eaten) into extinction — ie, eradicated — by our own species.
Koko's Place in our History
Regarding "Koko's place in our history," we think it is fair to say that Project Koko has changed the paradigm about our relationship to other species from domination to appreciation — and our perspective about gorillas from that of "King Kong" to "Koko's Kitten." Koko has also raised our consciousness by leveling the hierarchy between humans and other animals. Someday, people may look back on the reality shift caused by Koko as being almost Copernican in nature (ie, discovering the earth wasn't really the center of the universe).
Saving Her Species
Regarding Koko's role in saving her own species — which many humans view as an intrinsic benefit in itself — we can put it this way: In order to save or protect a species, people need to care about that species (ie, not just intellectually, but emotionally, empathetically); and "ambassador" Koko makes people care (thus the importance of her having/raising children).