The method the authors used was to go back into the records of ape (2 bonobos and a chimpanzee) usage and 2 toddler-aged children (1 to 2 years) and compare what that old data has to show about cooperative exchanges. The ape studies were conducted decades ago and were designed to answer the questions of that time. These days there is much more emphasis on the role of cooperation between humans and how that is reflected in speech, particularly in the speech triangle and declarative statements.

Declarative Statements

The paper has a couple of valuable charts that summarize what they found. The basic findings report what is already known, but it is useful to see numbers. The most important information is that the most common utterance among the apes were requests (ranging between 72% and 85% of all utterances). Meanwhile, this was the least common type of utterance among the children (about 10%). Requests are also what ape gestures are about: begging for food, encouraging a scratch. The part that surprised me was how low the share of children's utterances were requests.

Note: I'm using the term utterance and speak, but obviously the apes did not literally speak. They used sign language or a keyboard with signs on them.

The most common type of utterance among the children were declaratives (40% and 50%). This peak is much lower than the reflects the much wider range of utterance types used by humans. The declarative type is the lowest for the apes. Thus, despite the paper's dramatic title, apes do not really declare much. All three apes made declaratives less than 10% of the time, and it is only because of one of the apes (a bonobo named Panbanisha) that I even need to make the number that high. The other two apes are more like 5%. Other types of utterances listed are responses to caregivers and imitations. Humans outdo apes in both categories. One of the children was almost as likely to be making a response as to making a declaration.

Thus, while the stereotype of apes asking and demanding while people declare is a bit of a simplification, it is not that far off base. However, the authors do offer an important warning, "Ape caregivers tended to interpret any utterance as a request, unless behaviorally, the ape made it clear that they were not requesting an item. This tendency to ignore declaratives may have led the apes to make fewer declaratives." [p. 11]

They also analyze the declarative utterances of the speakers. The most common form of the children's utterances (about 55%) were classified as concrete. That is "pure naming;" for example, while eating an apple the speaker might utter "apple." It also turns out that some concrete names were "uttered" because the apes had learned that this was a good technique for activating the keyboard they used to communicate.

I was completely surprised by the information that apes make utterances about future plans as much as they engage in pure naming, while such speech is much less common among children. These are utterances about what the speaker is about to do. I shook my head in wonder when I saw that item and then laughed when I read the authors' comment on it: "This [declaration about future actions] highlights a distinct difference in the way caregivers interacted with apes vs. children. The caregivers exerted more control over the apes' movements, especially as they got older, while caregivers were more likely to engage in naming (as opposed to testing) interactions with the children." [11].

The business about controlling the ape movements reminded me of the movie Cool Hand Luke. Prisoners working on a chain gang had to tell the guards what they were going to do before wandering off to do it. The basic point about apes is that they are apes, not humans or even humans manqué. When they become more mature, they become more and more like apes and harder for their captors to control. In the wild, apes do not use sign language; captive apes can be trained to use signs, but even then they use the signs in a manner that reflects their captive state. The are not cooperating; they are submitting.

The Speech Triangle

The authors also looked for evidence of a triadic (speech triangle) relationship. About 1% of the total ape utterances "explicitly suggested a triadic interaction." [9]. An example: At just over two years of age the bonobo Panibasha was eating a strawberry. She went to the keyboard and "commented" on what she was eating. Her human attendant agreed she had a strawberry. This is not a very profound exchange, but it is typical of the kinds of things that go on between parent and small child.

The authors also note that "nfrequent phenomena… can be significant in evolution because natural selection sometimes utilizes genes for infrequent, but adaptive behavior. As the survival rate of individuals displaying said behavior increases, the behavior becomes more frequent" [3]. I agree with this statement, and feel that it supports what I have been saying since my original post. Apes are smart enough to use signs and make simple utterances. The fact that they do not make them without special training under abnormal conditions indicates that we have to look for some explanation for the rise of speech other than intelligence. The authors conclude:

the extreme rarity of these declarative events in wild apes as well as in our sample suggest that while apes have the biological capability to declare, there might be an environmental trigger that must occur to express this ability phenotypically. This is similar to the ''Vygotskian hypothesis'' that suggests that cooperative, declarative behavior is socially supported in humans, but [finding declarative statements] expands the range of possible social support to our evolutionary relatives, the great apes. For example, a environmentally-regulated gene that triggers declarative communication mechanisms may have become permanently expressed in humans within the evolutionary time frame of the development of human language. Thus a small change switches humans from ''capable of declarative communication'' to ''consistently declarative communicators.'' [11]

I think the rise of speech was more complicated than this passage implies, but it seems likely that we were on our way to primitive speech as soon as we became a cooperative species.