Interesting that you link to one of Gillian's papers, I met her in the 1980s.
From the full paper of the link you gave, regarding traditional method of abortion in Southern Arnhem Land women:
Voluntary controls are of course an important issue in any discussion of overall fertility.
A detailed survey of the available information on contraception, abortion and infanticide among Aborigines has revealed that Aboriginal women saw children as a contingent good (Cowlishaw 1979).
First there were widespread attempts at contraception by taking medicine, performing rituals and avoiding coitus.
Which poses the question, why avoid coitus if there is (as you claim) no understanding of fatherhood and conception.
From the full paper of the link you gave, regarding traditional method of abortion in Southern Arnhem Land women:
Which poses the question, why avoid coitus if there is (as you claim) no understanding of fatherhood and conception.