sItopanayana

Actual argument would be -

If there were female upanayana in R, it would be described + There is no description of female upanayana in the Ramayana => the author of the Ramayana never conceived of female upanayana.

Seems quite reasonable to me. If V finds R’s upanayana of note and describes it, no doubt he would do the same for S.

There are lot of other absences - absence of female Rtvik-s, female warriors (other than likes of tATakA and shUpraNakhA), famale ministers, female AchArya-s etc..

Probability calculation

Just for fun -

Events U = S’s upanayana K = described in rAmAyaNa

Bayes theorem IIRC -
P(U|~K) = P(~K|U)P(U)/(P(~K|U)P(U) + P(~K|~U)P(~U))

Prior probability P(U) = 0.05 P(~K|~U) = 1 P(~K|U) = 0.01

P(U|~K) = .01*.05/(.01*.05 + 1*.95) = 0.00052603892

Been a long time since I did this - so if there is an error, please let me know.