This piece still fascinates and stimulates me. I have found a detailed university research paper which explores the concept of 'art and costly signaling' and the manufacture of seemingly useless and time consuming products among plains people. It is a over 100 pages long with so very nice photos of late 19th century Sioux art. I have cut and paste a in a nut shell extract as well as a link. Long but well worth the effort rewarding you with enlightenment.
Hypothesis 1: Displays of body decoration and personal adornment by
nineteenth century Lakota tribal members operated as social signals of
prestige and skill, and were costly in terms of energy and resources.
These costs guaranteed that only those individuals who could bear
them would be able to produce the displays.
Hypothesis 2: Costly signaling through body decoration and personal
adornment by Lakota tribal members reliably indicated some hidden
trait or characteristic of the signaler, and in order to maintain the
honesty of these signals, some social mechanism operated to prevent
free-riders from faking signals.
Hypothesis 3: Costly signaling through body decoration and personal
adornment by Lakota individuals was beneficial to both the signaler
and receiver, resulting in a payoff of enhanced prestige at the level of
the individual.
http://digitalcommons.unl.edu/cgi/vi...t=anthrotheses