Parental investment and sexual selection

Charles Darwin's (1871) treatnent of the topic of sexual selection was sometinrcs confused because he lackcd a gcneral framework within which to relate the variables he perceived to bc important: sexlinked inheritance, sex ratio at conception, differcntial mortality, parental carc, and the form ot the brecding system (monoganry, polygyny, polyandry, or promiscurry/. This confusion permitted othcrs to attcmpt to show that Darwin's tcrminology was inrprecise, that hc n]isinterpr(]ted thc function of sornc structurcs, and that the influcnce of sexual sclectioD was greatly overrated. l luxley (1938), for cxample, dismisses the importance of female choice without elidcnce or theorctical arSument, and he doubts thc plcvalencc of adapta_ tions in males that dccreasc their chances oI surviving but arc sclcctcd bc_ causc thcy lcad to high reproductivc succcss. Somc imp,rttant i ldvances, howevgr, have becn achievcd sincc Darwin,s work. The p,cnetics of sex nas now becn clarif ied, and Fishcr ( 1958 ) hrs produccd , n,od"l to cxplarn sex ratios at coDception, a nrodel recently extendcd to include special mccha_ nisms that operate under inbreeding (Hunrilron I96?). Data frorn the iaboratory and the field havc conlirnred that females ar.e capable of vcrv sub e chrtices (for example, Petit & Ehrrnrn I 969 ), and Barentan ( I 94g) has suggested a general basis for female choice antl male-male competit ion, and he has produccd prccisc data on one species to support his at.gument.