ORIGIN OF LIFE ON THE SHORES OF THE OCEAN 109 



of organisms. In the earliest times it must have been the organic 

 molecules which preceded life that were so deposited. There they 

 would have been strongly absorbed by the clays. This is the 

 hypothesis I put forward some thirteen years ago, and I think 

 now it can claim a certain amount of support from experiment. 

 By such a mechanism of deposition and absorption it is possible 

 to build up quite a considerable amount of organic material layer 

 by layer as each deposit is put on top of the other. Every thick 

 clay bed today contains its appropriate amount of organic ma- 

 terial, in some cases very large amounts; there are marine clays 

 which contain as much as 2% of oil and this, indeed, may be the 

 source of most of the oils which are exploited commercially. 



This organic trapped material, however, does not usually remain 

 indefinitely in the clay of an active estuary; in most cases the clay 

 is in turn eroded by the runoff streams, and the mud is returned to 

 the general circulation of suspended mud. This will not be the 

 same as the original organic material for, while absorbed on clay, 

 it may have undergone chemical changes. This process of deposition 

 and erosion is repeated indefinitely and the whole material, 

 organic and clay together, is worked over and over again. As it 

 lies on the wet surfaces at low tides it is, of course, exposed to 

 sunlight, heated quite considerably, and liable to chemical changes. 

 Now one of the chemical changes which is the most interesting and 

 which has been checked by the work of Akabori (1959) has been 

 that of polymerization. He has actually carried out the experiment 

 of polymerizing the simplest amino acid, glycine, on a clay base 

 with ultraviolet light and finds it produces polyglycine. Such 

 polymerizations, but naturally much more complicated, must have 

 occurred on the early mud flats. The problem is to see not so much 

 how the polymer is formed but how it is removed from the clay, 

 and this still requires to be demonstrated. We may by a negative 

 argument postulate that this separation did take place because 

 polymerized colloidal substances are found in all organized bodies, 

 and on the other hand clay is not found in them. They must at 

 some point have separated themselves from the clay. 



Here my ideas rejoin those of the original Oparin hypothesis 

 that the polymerized materials, particularly if they are hetero- 



