By 50,000 years ago, the effects of a ‘symbolic explosion’ — an efflorescence of human art, song, dance and ritual — were rippling across the globe. Applied to archaeological evidence, standard neo-Darwinian theory offers new understandings of this improbable event. The present article defines ‘symbolism’, models quasi-ritual behaviour in late archaic Homo sapiens, extends the argument to the emergence of anatomically modern humans and concludes with preliminary tests against archaeological, ethnographic and rock art data.

A highly specific antiserum to rat GH (anti-rGH) was used to assess the role of GH in lactation in the rat. When administered alone, anti-rGH had no effect on litter weight gain, whereas bromocriptine reduced serum prolactin concentrations and litter weight gain for up to 7 days when given on day 4 of lactation. When bromocriptine and anti-rGH were given in combination, however, litter weight gain declined even more dramatically so that pups were receiving virtually no milk 2-3 days after treatment. Daily litter exchange failed to prevent this effect. Concurrent injections of highly purified GH (prolactin contamination undetectable) prevented the dramatic decline in litter weight gain induced by combined bromocriptine and anti-rGH treatment, so that these litters grew as well as those receiving bromocriptine alone. Growth hormone did not act by influencing serum prolactin concentrations, which remained low during GH therapy. Direct effects of anti-rGH or GH on the pups (transferred through the milk) were ruled out since virtually identical results were obtained when milk yield was estimated during a 30-min suckling period after a 3-h separation of mother and pups. Lactation had virtually ceased 3 days after treatment with both bromocriptine and anti-rGH, but it could be reinitiated by a single injection of prolactin or GH, and subsequent recovery was virtually complete. The results of this study show that prolactin can maintain a full milk yield in the absence of GH, milk yield is reduced by approximately 50% in the absence of prolactin and milk yield is totally stopped in the absence of prolactin and GH.(ABSTRACT TRUNCATED AT 250 WORDS)

IntroductionThe first obvious statement is that the mammary gland is an intriguing structure, and that its development is one of the most fascinating aspects. During the lifetime of the animal the mammary gland probably undergoes more and greater changes in size, structure

SUMMARYMeasurements have been made of body weight, mammary weight and total mammary DNA content (DNAt) during the second half of gestation and throughout lactation in mice. When cor;ected for conceptus weight and mammary weight, body weight was not significantly changed with advancing gestation but did increase during lactation. Mammary weight increased progressively until day 10 of lactation, then decreased until the end of lactation. On day 4 of