Meat was an important source of nutrition for ancestral humans (as it is today, MacDonalds aside). It has been suggested that the importance of meat meant that men often traded it for other favours such as forging allegiances or for sex  (Stanford, 1999 – see pages 101, 130 and 131 of our A2 Complete Companion). Observations of animal and human behaviour have been used to support this ‘meat for sex’ hypothesis, however a recently published study says the suggestion is baseless. Gilby et al. (2010) conducted an observational study of chimpanzees over a 28 year period (see here and here) and found no evidence that males hunted more when females were most fertile, nor were they more likely to share meat with fertile females. However there continues to be evidence that supports the meat for sex hypothesis (see here). This study  by Gomes and Boesch (2006) found direct evidence of meat exchange in another study of wild chimpanzees. It may be that males exchange meat on a long-term basis i.e. they don’t do it just when a female is fertile but provide meat continually so they can take advantage of fertile periods when they occur.