If sexual selection is ruled out, then what other possibilities remain? I see two: 1. music may have prepared the way for the development of language; 2. music may have played a role in the development of certain uniquely human social skills, especially the very close and precise cooperation needed to both fend off predators and hunt big game.
I'll leave aside the very difficult issue of the association with language for the moment, to concentrate on the relatively straightforward issue of cooperation. And no sooner did I raise this issue here than an answer has magically appeared as I (just now) did a Google search on "cooperation among bonobos" -- and instantly found this article, entitled, Sex and co-operation - it's the bonobo in you. Here's how it starts: "Could there be more of the bonobo in us than the chimpanzee? And does this explain the extraordinary ability of humans to co-operate with each other to create everything from a symphony concert to a space station?" Here are some more intriguing bits:
To find out how co-operative bonobos were, [Vanessa] Woods and her colleagues tested those living in the Lola ya bonobo sanctuary in the war-torn Democratic Republic of Congo, and compared their performance with that of chimps.
Pairs of apes were presented with a long plank with food on it and a rope threaded through either end. If the two chimps or two bonobos pulled together, they could get the food.
When there were two bowls of fruit, chimps would work as a team to get the goodies, as long as they knew and liked each other.
When there was only one bowl, or they were paired with a chimp they did not like, co-operation fell apart. "They wouldn't do it any more," said Ms Woods. Bonobos, on the other hand, did not care who their partner was, nor how much food was on offer.
First of all they spent some time playing and engaging in sexual behaviour. Then they each grabbed one end of the rope, slid the tray towards them, and shared the spoils. "They were better co-operators than chimpanzees," she said.
The study, published in the journal Current Biology, has revealed the importance of social tolerance in the development of co-operation. "What probably happened with humans when we split from our common ancestor with chimpanzees and bonobos 6 million years ago is that we became very tolerant [like bonobos], which allowed us to compete in ways that had never been seen before."
I've seen similar reports describing how Bonobos, unlike Chimps, will routinely share a portion of food with other Bonobos, even when they're in separate cages. What makes such results especially interesting is that 1. Pygmies and Bushmen are also known for their willingness to freely share food and other valuable items; 2. Bonobos, unlike Chimps, vocalize in a manner that resembles certain aspects of Pygmy and Bushmen communal singing. To clarify, here are some relevant excerpts from an article on primate vocalization, by Björn Merker, that I quoted back in Post 21:
Synchronous calling of the kind postulated here, that is, true cooperative synchronous calling rather than synchrony as a default condition of competitive signaling, requires a motivational mechanism for mutual entrainment. We assume that such a mechanism was selected for in the course of hominid divergence from our common ancestor with the chimpanzee, and was retained to the present day in the form of our propensity to join in and entrain to a repetitive beat. This propensity is apparently lacking in the common chimpanzee, which seems unable to keep time even with training ..., but may be present in bonobos. . . Genuine synchronous chorusing may exist, at least incipiently, among bonobos. A report by de Waal ... on captive bonobos describes a call variant apparently lacking a homolog in the vocal repertoire of common chimpanzees, namely, a loud and explosive sound called staccato hooting. According to de Waal “during choruses, staccato hooting of different individuals is almost perfectly synchronized so that one individual acts as the ‘echo’ of another, or emits calls at the same moments as another. The calls are given in a steady rhythm of about two per second.” (from Björn Merker,"Synchronous Chorusing and Human Origins," in Wallin, N. L., B. Merker & S. Brown (eds), The Origins of Music. Cambridge, MA: MIT Press, 2000, p. 318-319).
While Merker seems primarily interested in "entrainment" as the precursor of synchronous singing among humans, what leaps out at me is de Waal's description of hooting Bonobos echoing one another in almost perfect synchronization, which calls to my mind the auditory image of hocketed yodeling among Pygmies or Bushmen. ("Hocketing" is the breaking up of a musical line into fragments, echoed back and forth among two or more performers.)
No more for now. I'll be out of town for a week or so and away from my computer, so may not be doing much blogging till I get back.