H.— ANTHROPOLOGY. 183 



we take it that, with diminished hair-growth, the influence of the thyroid 

 secretion has been liberated to exert itself elsewhere, and, as we understand 

 its relations with brain-growth are also close, we may see in this an accessory 

 factor of brain-growth in man. 



The increased brain-growth, whatever its causes, is an outstanding 

 fact of human development, and the corresponding increase of the volume 

 of the skull has apparently made the training for the holding up of the head 

 a longer process, consequently the helplessness of the infant, the oppor- 

 tunities for maternal care, and the delaying of hair-growth are all empha- 

 sised. The process of brain-growth and delay of skull-hardening can also 

 be prolonged still further as infancy is lengthened. 



The changes just noted have doubtless contributed, from early stages, 

 to the differentiation of men's and women's activities, a differentiation 

 which is a marked feature of our race,'' for, among other mammals, the 

 two sexes for the most part share much the same habits and run together, 

 though there are well-known partial exceptions. The emphasis on this 

 differentiation of work between the sexes seems to have arisen as man 

 was becoming man in a fairly full sense, and we can hazard an hypothesis 

 as to how it came about. 



Man's animal relatives search out nuts and fruits and various forms of 

 vegetable food, and occasionally indixlge in animal food ; man, even as 

 early as the middle Pleistocene, and probably even earlier still, was partly, 

 perhaps largely, carnivorous. Though General Smuts warns us against 

 overweighting European evidence, we must agree that the Euro-Africo- 

 West- Asiatic quadrant of the world was a very important home of early 

 and mid-Pleistocene man. The cold winter anti-cyclone of that period 

 limited vegetation severely, and, while much of mid-Pleistocene Europe 

 was ice-covered, the belts of climate were shifted southward,^ so that 

 parts of the Sahara and Arabia got winter rain and were more grassy than 

 now. Lands with climate most suitable to the type of modern man (see 

 details below) would thus be largely grasslands, and here the food problem 

 seems to have urged the men towards hunting, while the women were 

 occupied with maternal duties, probably more necessary imder mid- 

 Pleistocene conditions on the grasslands than in earlier times. The 

 success of hunting in providing energising food which helped to maintain 

 body-heat under cold conditions, and generally promoted activity, must 

 soon have become evident, and man became largely a hunter. Women 

 seem to have continued more or less the traditional gathering, but there 

 were no doubt many grades and variations in this differentiation of work. 

 It was not the substitution of a largely carnivorous for a largely vegetarian 

 diet which was so important ; rather should we emphasise the supple- 

 mentary natures of the two diets among people who had not yet the 

 assured position of food-producers. The strenuous exercise of hunting, 

 using the accompanying increase of energising food, would prolong growth 

 and probably retard the oncoming of sex-maturity in the young men. 



It is noteworthy that among hunting peoples the difference in stature 

 between the two sexes is still often much greater than it is among culti- 

 vating peoples. Here, again, we seem to get another indication of the 



8 Thomson, J. A. ' What is Man ? ' 1923. 



* See discussion in Journ. Roy. Anthr. Inst., L, 1920, 



