By telling students that the beliefs of a superstitious tribe thousands of years ago should be treated on an equal basis with the evidence collected with our most advanced equipment today is to completely undermine the entire process of scientific inquiry.
And one more thing: In your original message you identified yourself as an elementary school teacher. If you are going to insist on holding to a creationist viewpoint, then please stay away from my children. I want my kids to learn about “real” science, and how the “real” world operates, and not be fed the mythical goings-on in the fantasy-land of creationism."
Monkeys/apes/gorillas may have vocal cords, but they are in a different position than ours. Our vocal cords have migrated down the throat. This change also makes us more susceptible to choking than chimps, as there is a bigger likelihood of food entering the air passages to the lungs. In fact, infant humans have their vocal cord in a different position than adults when they are born. Only as infants grow do their vocal cords migrate towards the adult position. As you probably know, infants are not very good at speaking and they are much better after they have become toddlers. Besides the vocal cords, our hyoid bones have also moved, so they are able to support and move the tongue better. Moving the tongue and our mouth more precisely also allows us to produce a wider variety of sound. The result is that we are able to produce more sounds than most other animals.
"Fine manipulation of the larynx is used to generate a source sound with a particular fundamental frequency, or pitch. This source sound is altered as it travels through the vocal tract, configured differently based on the position of the tongue, lips, mouth, and pharynx."
The ability to produce sound is obviously a pre-requisite, but our brains have to be able to process speech. It has to control the fine movement of the vocal cord (larynx) to be able to produce the sound. Some birds are able to do the same. Their brain can control their “vocal cords” (syrinx) so that they can produce a wide variety of sounds. Parrots that can imitate speech exhibit handedness. Most parrots capable of speech are left footed, as their right brain are used to control sounds. The right brain has the ability to move their syrinx precisely, which also enable them to move their left foot precisely. As a result, these parrots prefer to use their left foot when they need to manipulate objects, such as food, since they can do it better than with the right foot. A vast majority of humans, OTOH, control speech with the left brain, so our right hands are able to manipulate things better and we prefer to use it to write because writing requires fine manipulation of the pen. People who are left handed tend to have the right brain controlling speech. Chimps are not left-handed or right handed, which means they lack a brain that can finely control the movement of their hand or their vocal cords.
Finally, humans have a unique version of the FOXP2 gene that is linked to our speech. The chimpanzee version of this gene has two different amino acids than the human version. People who have a damaged version of the FOXP2 gene have speech disabilities. It is not clear whether Neanderthals have the human version of the FOXP2 gene. Some recent reports claim that they did, but others pointed out anomalies with the DNA sequences, which suggest either interbreeding or contamination as the reason for the finding Neanderthals have the same FOXP2 gene as humans. Since other studies suggest Neanderthals did not interbreed extensively with modern humans, if they interbred at all, contamination appears more likely. Therefore, a large number of different things have to change for humans to speak. These include moving the larynx further down the throat, moving the hyoid bone to better manipulate the tongue, evolving a brain that is capable of fine movement of the vocal cords, and 2 new amino acid substitutions in the FOXP2 gene. The fact that we have more facial muscles than most other primates may also play a role, since the ability to move our lips and mouth can help us produce even more sounds. There is no doubt then that natural selection was responsible for all these changes which help us achieve speech. Since other animals lack the same anatomical features that enable human speech, with the exception of some parrots and a few other passerine birds, which have some of the these features, they are therefore unable to make as many different sounds as humans.