In case its full significance might have eluded you, I'd like to repeat the last sentence of the "Author's Summary" as quoted in the previous post, with some added emphasis: "This finding suggests that the shared physical and cultural features of Pygmies were inherited from a common ancestor, rather than reflecting convergent adaptation to the rainforest.." The most obvious of the shared physical features is, of course, short stature. The gene or genes controlling human stature have not yet been isolated, but given the shared lineage implied by both the mitochondrial and autosomal (i.e., nuclear) DNA evidence it seems safe to infer that both the Eastern and Western Pygmies inherited their short stature from a common ancestor.
An alternative theory popular among anthropological "revisionists" is that the Pygmies as such do not really have a shared lineage but are simply Bantus whose ancestors happened to settle in forest areas. According to this line of thinking, their short stature is the result of convergent evolution, i.e., totally independent but very similar processes stemming from the adaptation of each group to the special conditions of life in the tropical forest.
It's important to note, at this point, that there is no way of proving beyond the shadow of a doubt that the common ancestor of today's Pygmies was short. There will always remain the possibility of convergent evolution, even if it can be proven that they all share a common ancestor -- because, strictly speaking, we have no way of proving that ancestor could not have been tall. Which brings me to a very important, though often overlooked, aspect of modern science, a principle known as "Occam's Razor," which has been summarized as follows: "one should not increase, beyond what is necessary, the number of entities required to explain anything."
The basics are explained in a particularly clear online discussion by Francis Heylighen:
[Occam's Razor] underlies all scientific modelling and theory building. It admonishes us to choose from a set of otherwise equivalent models of a given phenomenon the simplest one. . .An excellent example of Occam's Razor is provided by the application of Newton's principle of universal gravitation to our understanding of the planetary orbits. Strictly speaking the ancient Ptolemaic theory of planetary epicycles, based on an Earth-centered universe, could, in Newton's day, account just about as accurately for the planetary movements as Newton's theory. Without a principle such as Occam's Razor, we might want to consider both theories as equally acceptable, since both are capable of fully accounting for the data. However, Newton's explanation, being far simpler than that of Ptolemy, satisfied Occam's Razor, and thus became universally accepted in his day -- despite the fact there was, at that time, no way of knowing for sure that the planets did not revolve around the Earth in complex epicycles after all.
Though the principle may seem rather trivial, it is essential for model building because of what is known as the "underdetermination of theories by data". For a given set of observations or data, there is always an infinite number of possible models explaining those same data. This is because a model normally represents an infinite number of possible cases, of which the observed cases are only a finite subset. The non-observed cases are inferred by postulating general rules covering both actual and potential observations.
Thus, according to very basic scientific principles, when we reach a point that two or more theories account equally well for all the evidence, Occam's Razor more or less compels us to accept the theory offering the simplest explanation. Which does not rule out the possibility that new evidence might some day arise that might force us to reconsider.
All too often in the social sciences we find people who are unaware of Occam's Razor, or believe they can easily ignore it, assuming it's necessary to demonstrate the impossibility of every alternative before any theory can be accepted. Not true. All that should be necessary to establish a given theory is to demonstrate 1. that it fully accounts for all the currently available, relevant, evidence; and 2. that it presents a simpler explanation than any alternative which may also happen to account for the same evidence. That doesn't mean the theory is necessarily proven, i.e., true for all time. Absolute proof, contrary to popular opinion, is not the objective of scientific inquiry.
I would now like to return to the sentence quoted at the beginning of this post, but with a different emphasis: "This finding suggests that the shared physical and cultural features of Pygmies were inherited from a common ancestor, rather than reflecting convergent adaptation to the rainforest.." The inclusion of the term "cultural" opens up a whole new vista, rarely considered in the genetic research, but definitely worth considering here. Because, despite the indifference of most ethnologists to this line of research, it most certainly has relevance for our understanding of culture and cultural evolution, which, operating via ancestral traditions passed down from generation to generation must also be regarded as "genetic."
While Patin et al. focus on cultural practices associated with subsistence, such as hunting, gathering, honey collecting, etc., other distinctive cultural features, such as nomadism, acephalous leadership, egalitarian social structures, gender equality, non-violent behavior patterns, and, of course, distinctive modes of dancing and music-making, would also, according to the same set of findings, and the same scientific (i.e., Occam-based) logic, be due to inheritance "from a common ancestor."
Consequently: if the simplest interpretation of the genetic evidence points to a common ancestor for all Pygmy groups, and the simplest interpretation of that finding points to the same common ancestor as the most likely source of all the other commonalities, both physical and cultural, then we may safely infer that our musical "time-machine" takes us back at least 18,000 years into the past, i.e., well into the Upper Paleolithic. But that's only the beginning -- because we have yet to factor the Bushmen and their music into the equation.
(to be continued . . . )
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