Grabbed from my furl.
Menstruation, he suggests, functions as a signal. It lets men know that the woman will refuse sexual intimacy. But this is not enough ; all fecundable women must signal their refusal at the same time. Knight needs to demonstrate that this is possible. He begins by noting that although the menstrual cycle is not necessarily linked to the phases of the moon – periodicity among primates is variable – the typical cycle of the human female lasts 28.5 days, and coincides exactly with the lunar cycle. Next, Knight cites the results of some research that indicates that when women spend enough time together – in a boarding school, for example, or a university dormitory – they tend to have their periods at the same time. Women, then, are capable of menstrual solidarity, and of clearly demonstrating, all together, that they are not disposed to have sexual relations. They use the moon and the tides to synchronize ; at the new moon, women have their periods. They remain shut away in their homes. They mock the men, as Sharanahua women still do today : “There’s no meat in the house”, they say, “we’ll eat penises”. The men, thus reminded of their human duties – duties of exchange and reciprocity – get together to organize the hunt. They will return, says Knight, around the full moon, loaded with meat.
To accomplish their tasks, ancestral moms would at times have needed to put their babies down, and these interruptions in physical contact would have been as distressing for infants then as they are now. It’s very likely that mothers began to use special vocalizations to reassure and quiet their infants. These vocalizations were the origin of the more complicated lullabies and baby talk, sometimes called “motherese,” that exist today in nearly all human cultures, but which are totally absent among chimpanzees. Motherese helps infants learn the rhythms and rules of their native speech through simple vocabulary, extensive repetition, exaggerated vowels, high tones and slow tempo. The road from mothers’ reassuring vocalizations to the first speech would have been a long one, but these interactions between prehistoric mothers and infants may very well have paved the way for the emergence of spoken words.