One of the greatest satisfactions of writing this blog for five years (and I hope also of reading it) has been the much sharper understanding I gained about how language works. As a professional writer my whole adult life (and an apprentice writer for most of my childhood) I liked to think I had a decent understanding of the way language worked, but this blog has brought old instincts and habits into consciousness. I've made a few corrections, as a result.
I'm not sure that is entirely true. Adult animals sometimes teach the young by demonstrating. Mama lions bring small, captured prey to their growing cubs to learn killing. Since there is no talking, the prey isn't a topic, but perhaps it is a prototopic, a shared point of interest. I mention this because it indicates that once things had names no further evolution was required to turn those things into topics.
We also know from experiments that apes can make words in sign language. They don't engage in the kind of chatter fantasized in the movie Rise of the Planet of the Apes, but they are able to provide the correct sign when asked to identify many things, such as a bird or a cow.
Examples like these suggest that the ability to recognize potential topics is much older than speech itself. What was needed was not a topic-spotting skill but a motive to consider a topic. Really, dual motives are needed. The speaker needs a reason to draw attention to the topic, and the listener needs some reason to care about and trust in what the speaker says. This kind of dual motivation is cooperative. Thus, it didn't take the evolution of a new curiosity about the world to add topics to the speech triangle.
Work with apes and sign language have made it pretty clear that apes cannot put together a subject and a predicate to form a true sentence even though sign language is perfectly capable of expressing a complete idea. James Hurford has described this advance as the introduction of news, although one can argue that the speaking of a topic alone presents news.
The critical advance is the transformation of two points of attention into a unified whole. I could say, "Mother. Apple pie," and produce a kind of emotional or associative collage. A sentence goes beyond collage by fusing the two parts. A sentence like, "Mother burnt the apple pie," combines the two foci, thanks to the verb which functions with both noun phrases (mother burnt … burnt the apple pie). If the verb doesn't work with both foci (e.g., mother swam … swam the apple pie), the sentence is meaningless.
Since apes cannot construct such sentences, our ability to do so must result from some evolution. We have to be able to link two things at once to produce a new whole. There is archaeological evidence of this ability in the Acheulean axes. About 1.8 million years ago, Oldowan tools—stone flakes that are sharp on one side—began to be replaced by axe-like stones that had been sharpened on both sides to produce a chopping edge. It's an open question, whether this ability to make an axe head is related to the ability to produce sentences. It would be nice if a strong link could be established because then we could give a date as to when sentences were possible.
Modern sentences can be much more complicated than subject + predicate. William Faulkner was a master of elaborate sentences, one of which reads: "The store in which the Justice of the Peace's court was sitting smelled of cheese." The subject and predicate are united in the classic manner ( the store smelled … smelled of cheese) but there is a long aside that inserts a second, more challengingly organized, sub-sentence (in which was sitting … was sitting the Justice of the Peace's court). Did we have to evolve something new to add a subordinate clause to a sentence?
I don't know, but I doubt it. Languages have so many twists and turns, and they vary so much. I'm inclined to say that normal changes in language overtime is sufficient to account for the syntax that follows the union of subject and predicate. But others have other opinions and I'm open to experimental evidence. In particular, I wouldn't be surprised to learn that the scaling up of the brain was required to handle more complex sentences.
When you focus on topics, however, the issues are different from syntactical matters. Instead of worrying about recursion and move rules, there is the steady straying from physical reality by topics. Apes and toddlers name concrete things, but there is more to talk about than things that can be sensed. In particular, things that happen internally cannot be named directly.
A common internal experience is feeling hatred. How do you talk about that in concrete words? The Bible, when talking about Pharaoh's returning hatred for the Jews of Egypt says his heart hardened. Even people who call themselves literalists don't take that one literally. It's a metaphor for the changing feeling going on inside the pharaoh.
The ability to handle metaphorical topics probably evolved. I'd like to see an ape understand one. Also, not every human can understand metaphors. It is particularly common for autistic spectrum people to have trouble with them for they find them illogical. How could pharaoh's heart harden without killing him? This kind of problem suggests that there is something in a normal human brain that understands metaphors and that doesn't work properly in autistic brains. Other explanations, however, may be possible.
Finally, the most abstract topics are concepts. Whether we needed to evolve a special brain function to handle concepts is not clear.
One thing that is very apparent about metaphorical and conceptual language is that it uses the same structure as concrete language. A sentence like ,"There is no justice in that courtroom," makes justice sound like a physical thing. Even if we speak more abstractly, "The system is unjust," we are talking as though the system exists and unjust is a real property, like, "The apple is red." Languages don't seem to distinguish, at least syntactically, between abstract topics and concrete ones. It suggests to me that while topics have been evolving, syntax has not.
Of course, getting at the bottom of these details calls for much more study, but it seems plain that the topic part of the speech triangle has a more complicated history than appears at first glance.