ra uss , ▁this ▁kind ▁of ▁work ▁was ▁considered ▁" anal yt ical ▁in ▁appearance ▁only ." ▁It ▁results ▁in ▁a ▁chart ▁that ▁is ▁far ▁more ▁difficult ▁to ▁understand ▁than ▁the ▁original ▁data ▁and ▁is ▁based ▁on ▁arbitrary ▁abstra ctions ▁( emp ir ically , ▁f athers ▁are ▁older ▁than ▁sons , ▁but ▁it ▁is ▁only ▁the ▁research er ▁who ▁decl ares ▁that ▁this ▁feature ▁explains ▁their ▁relations ). ▁Furthermore , ▁it ▁doesn ' t ▁explain ▁anything . ▁The ▁explanation ▁it ▁offers ▁is ▁t aut ological – if ▁age ▁is ▁cru cial , ▁then ▁age ▁explains ▁a ▁relationship . ▁And ▁it ▁does ▁not ▁offer ▁the ▁possibility ▁of ▁infer ring ▁the ▁orig ins ▁of ▁the ▁structure . ▁ ▁A ▁proper ▁solution ▁to ▁the ▁puzz le ▁is ▁to ▁find ▁a ▁basic ▁unit ▁of ▁kin ship ▁which ▁can ▁explain ▁all ▁the ▁variations . ▁It ▁is ▁a ▁cluster ▁of ▁four ▁roles – bro ther , ▁sister , ▁father , ▁son . ▁These ▁are ▁the ▁roles ▁that ▁must ▁be ▁involved ▁in ▁any ▁society ▁that ▁has ▁an ▁inc est ▁tab oo ▁requiring ▁a ▁man ▁to ▁obtain ▁a ▁wife ▁from ▁some ▁man ▁outside ▁his ▁own ▁her edit ary ▁line . ▁A ▁brother ▁may ▁give ▁away ▁his ▁sister , ▁for ▁example , ▁whose ▁son ▁might ▁reci proc ate ▁in ▁the ▁next ▁generation ▁by ▁allowing ▁his ▁own ▁sister ▁to ▁marry ▁ex og am ously . ▁The ▁underlying ▁demand ▁is ▁a ▁continued ▁circul ation ▁of ▁women ▁to ▁keep ▁various ▁cl ans ▁peace fully ▁related . ▁ ▁Right ▁or ▁wrong , ▁this ▁solution ▁displays