22 



LIFE: ITS BEGINNINGS AND NATURE 



escaped the solar system, the larger and 

 denser of these whirlpools were able to 

 coalesce by the forces of gravitation and to 

 attract additional matter into them. After 

 some millions of years, these planetary nu- 

 clei had grown slowly and steadily by 

 accretion into the solid planets we know 

 today. 



We are concerned with the conditions of 

 the earth in this early period that led to 

 the formation of the first living things. 

 What were the physical factors that pro- 

 duced a setting in which such a delicately 

 adjusted thing as life could have established 

 itself? 



At first a thin crust formed over the 

 bottomless sea of molten rock; because of 

 the tremendous heat, water could not exist 

 at the surface, so a thick gaseous layer of 

 superheated steam covered the entire 

 earth. As the steam pushed upwards into 

 the cooler regions, condensation occurred, 

 causing dense fog and torrential rains. 

 Eventually, after still further cooling, the 

 rain drops penetrated the heat and reached 

 the hot rocks below, only to evaporate as 

 steam once more. Finally, however, with 

 further cooling, water stayed in the de- 

 pressions of the earth's extremely wrinkled 

 surface, forming the infant oceans of the 

 world. Hot rivers formed, of course, which 

 were forever rushing to fill the oceans, 

 carrying with them any minerals of the sub- 

 stratum that would dissolve. These sub- 

 stances were deposited in the young oceans, 

 resulting in a constant increase in the 

 chemical composition there. Water evapo- 

 rated from their great surfaces, just as it 

 does today, leaving the heavier salt par- 

 ticles behind and thus continually raising 

 their total salt content. That is why the 

 ocean water of today is salty. The im- 

 portance of these great bodies of water lies 

 in the fact that undoubtedly life originated 

 in them, sometime during this early stage. 

 Here, then, we see a spinning new world, 

 sufficiently far from the sun to be moder- 

 ately warm in most of its parts and fixed 



in a never fluctuating orbit, which insures 

 evenly spaced seasons. The surface is cov- 

 ered with rocks, gravel, sand, great water 

 masses, turbulent streams of cool to warm 

 waters, but no soil. A thick homogeneous 

 gas, rich in nitrogen and oxygen, envelops 

 its surface, with clouds of water vapor lazily 

 floating with the moving air currents. This 

 is the setting in which life started; this is 

 the world that gave birth to that dynamic 

 something which, once initiated, extended 

 into every part of that world. As it ex- 

 tended it became more and more diversified. 

 Finally it gave rise to human beings who 

 can sit here now and consider how it all 

 came about, a wonderful series of events, 

 and certainly fascinating enough to stimu- 

 late the curiosity within us. 



THE NATURE OF THE PHYSICAL 

 WORLD 



There are certain physical laws that 

 influence all things, animate as well as 

 inanimate, in the universe; therefore, it is 

 well that we learn something about them, 

 before we attempt to study life itself. 



All things in the universe are composed 

 of matter, and, since living things are de- 

 rived from material in the world, they are 

 also composed of matter and therefore be- 

 have as matter does. One of the character- 

 istics of matter is that it occupies space 

 and has mass. Mass may be defined as the 

 amount of matter in a body which can be 

 measured in terms of resistance to change 

 of motion. This is more meaningful when 

 it is considered in the light of attraction 

 between bodies. Bodies attract one an- 

 other according to their respective masses. 

 For example, the earth has a greater attrac- 

 tion (gravity) for a man than does the 

 moon because the earth has greater mass. 

 We have a convenient method of measuring 

 this attractive force between bodies; we 

 call it weight. Weight, of course, changes, 

 depending on where it is taken. A person 

 weighing 180 pounds on the earth would 



