INTRODUCTION TO THE METHOD ' 



tion, but it is sufficient to indicate how a factual record of evolution within a small 

 group could be pieced together and to see how the periodic repetition of a few simple 

 processes such as hybridization and chromosome doubUng can give rise to a cluster 

 of species of different ages which, it may be said in passing, have no doubt been subjected 

 at every stage to natural selection but have not been caused by that process. 



We could multiply examples, choosing other and better instances, but this is perhaps 

 enough to introduce the subject to an impatient reader who, at this point, may legiti- 

 mately be expected to ask 'What, after all, does this amount to? You have shown, it is 

 true, some facts about the mode of origin of a few rather trivial species and have traced 

 some events in their past history, extending some pakry thousands of years beyond our 

 little human lifetime, but is this Macroevolution?' 



And this, of course, is the unsolved question. The interest of cytogenetic analysis 

 lies in the fact that it does indeed permit of some extension bacEwards in time beyond 

 our own very Hmited experience, and that it provides some phyletic information regard- 

 ing more important natural units than the artificially produced varieties of domesticated 

 animals and cultivated plants. But the gulf between this and macroevolution in the 

 literal sense is enormous. The tremendous changes recorded in the rocks and in the 

 taxonomic systems of the plant and animal kingdoms are so greatly different in degree 

 from anything which our existing analysis has so far touched that we cannot with 

 certainty know whether they may not also be different in kind. In that case we should 

 have in the end to admit that all our present tools can only touch the fringe of the 

 subject, and that such knowledge as we can acquire of the origin of species does not 

 necessarily provide the clue that we are seeking. 



A decision as to this, however, may perhaps be left in the hands of our imaginary 

 historian who, from his vantage point in the twenty-first century or later, ought to be 

 able to see things in better perspective than is attainable by us. For ourselves we may 

 be satisfied with the knowledge that with some new tools in our hands we have a large 

 new field to explore, and if our exploration does not resolve the major problems of the 

 organic world, we may at least look forward to some enjoyable experiences which 

 may enhance our interest in some famihar and common plants. 



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