Page Six 



EVOLUTION 



October. 1928 



Brains — How Come ? 



By Allan Strong Broms 

 III. 



IIJ'IND and body are an inseparable pair. Always working to- 

 getlier on their one job of living, they just had to grow up 

 together. Certainly we cannot understand the evolution of either 

 without considering the other. In our story of man and his mind, 

 we have already found that it took a partnership between hands 

 and brain to make a man of him and 

 that his wise eyes did their new tricks 

 of seeing and judging only when they got 

 rightly connected in the switchboard of 

 the brain. 



But these are just recent, finishing 

 touches, well within the last ten million 

 years or so, the big start having been made 

 by our remoter ancestors some hundreds 

 of millions of years ago. For back of the 

 ape-man and man-ape, back of monkey 

 and tree-shrew, we must look to the pri- 

 mitive mammals, just emerging from the 

 reptile ranks, to find the really big advance 

 from which brains resulted. That big start 

 dates from the acquiring of warm blood. 



Our earlier ancestors, the reptiles, am- 

 phibia and fishes, were cold-blooded and 

 led but sluggish lives. Some were capable 

 of bursts of speed, but normally they just 

 dozed around. Compare the energetic 

 mammals or birds, both warm-blooded. 

 All animals are engines that burn food- 

 fuels within their bodies to keep them- 

 selves going. The cold-blooded tribe are, 

 however, of the low-pressure type, generat- 

 ing only enough energy to get by, while the 

 warm-blooded, high-pressure mammals and birds are a peppy lot, 

 always on the go. The net result for them was bigger and better 

 brains — as we shall see. 



What started them off? Bad weather, probably. Perhaps the 

 first of a long string of Ice Ages that repeatedly chilled off much 

 of this world of ours. When the old cold-bloods get caught by 

 freezing weather, all they can do is freeze up, too, and wait for 

 the next thaw to revive them. But when this big freeze came on 

 there was no thaw for thousands of years, and most of the numer- 

 ous reptile tribe were wiped out. 



A relative weakling among them, a rep- 

 tilian-mammal, had acquired the trick of 

 carrying his own warm climate around 

 within himself. This helped him get 

 through the long winter. Evidently the big 

 bullies of his world had kept him chasing 

 around so fast that he developed the hust- 

 ling disposition, for which good, warm 

 blood was necessary. He raised a whole 

 crop of warm-blooded and active descend- 

 ants, — predatory carnivores, hoofed herbi- 

 vores, and some little insectivorous tree- 

 shrews that led on to monkeys and man. 

 His tribe took possession of the world, and 

 blocked any real reptilian come-back. 



His blood itself contained more iron — 

 the real bearer of o.xygcn, — but he 

 also evolved ways and means of making 

 and keeping it warm. He grew himself an 

 overcoat — hair or fur. The birds used down 

 and feathers. He developed mammalian 

 legs, long and strong, to lift his body off 

 the chilling ground. Most of the reptiles 

 just squatted, — ani froze. His four- 

 chambered heart s opped the old leaks 



Growth of Mamuinl Br.Tiiis. Earli pair 

 from ancient auil modern animals of 

 similar kind and body bulk. 

 Arctocyon A Dog 

 Phenacodus B Pig 

 Coryphodon C Rliinoeeros 

 Uintatherium D Hippopotamus 

 Note decrease in olfactory (smell) lobes. 



:z 





UfWR 40 

 CRFIACEOOS 



UPPER 

 CARBO- 35 

 HIFtROUS 



LOWER 

 CARBO- 35 

 NlfEROUS 



DEVONIAN 

 so 





n*Rsui>po-pt»crNT*LS 



The Family Tree 

 According 



through which waste-filled blood had Jiixed with the clean, food- 

 and-air-filled stream. Also his heart was more vigorous in pump- 

 ing the blood around. Bigger lungs, worked by an active dia- 

 phragm, provided the forced draft of fresh air that kept the food- 

 fuels burning intensely. For fresh air plus food-fuels yield living 



energy. Necessarily he also ate oftener and 



more heavily. 



But there were hot days and hot spots, 

 too, when he had to keep cool or burn out. 

 Of course, he observed the usual hot 

 weather rules, ate little, kept quiet and 

 drank much. Drinking helped a lot, for 

 he had acquired a new trick, — he could 

 sweat. Sweating cooled him, for the moist- 

 ure, evaporating, absorbed heat, much of 

 it from his body. Also he installed a new 

 thermostat unit in his brain, which auto- 

 matically controlled all the valves and 

 dampers and what-nots of his system, to 

 keep him cool on the hot days and warm 

 on the cold ones. He was all fitted out 

 to go anywhere and stay through all the 

 seasons. Best of all, he had pep. He 

 could hustle a better living, — those bigger 

 and more frequent dinners he needed to 

 keep up the new pace. For this new pace 

 was faster. The world was soon full of 

 hustlers, — active mammals and birds every- 

 where, all looking for dinners, each trying 

 to escape becoming someone else's dinner. 

 The struggle for existence became more 

 intense and only the very fittest survived. 



Natural selection was right there to hunt out improvements and 



preserve them. Evolution speeded up. 



The big improvement was a better brain. Rather it was a 

 new brain area, the neopallium, a clean switchboard not all clut- 

 tered up with old, poor connections. It did not happen in a day, 

 of course, but evolved slowly, adding a part here for one job, 

 another there for the next. Some parts gathered sight knowleHge, 

 others knowledge from smell or taste or touch or hearing. Certain 

 portions took on the job of keeping the several parts in touch with 

 each other, so they could compare ideas and make well-considered, 

 joint decisions. Out of all this, slowly, 

 came the human brain, so far the last 

 word in its capacity to tackle new prob- 

 lems and adapt action to solve them. 



His better brains made the mammal ad- 

 aptable, — if he was careful about not spe- 

 cializing his body too much. Of course, 

 if he took to the water as a fish-shaped 

 whale, he could not expect to grow hands 

 with which to do clever work and experi- 

 ments. The birds tried over-specialization 

 for flying purposes and it left them — up 

 in the air. No hands, you see, — beaks be- 

 ing poor substitutes. Man's ancestors 

 somehow stuck to the middle road, kept 

 their adaptable bodies and cultivated the 

 adapting brain. They could meet new con- 

 ditions by changing their ways, without 

 waiting for evolution slowly to transform 

 their bodies. So they got by more often, 

 raised more youngsters and passed their 

 better brains along. 



Less hindered by climate, they travelled 

 and saw the world. Always on the go, 

 they bumped into all sorts of things, — 





of 



the .\nimals. 

 Wr 



K. Gregory 



