EVOLUTION OF LIFE ON THE EARTH 5 



since pigeons are particularly suitable for such experiments. 

 Pigeon breeding was pursued by the ancient Egyptians 

 3,000 years B. C. In Roman imperial times enormous sums 

 were spent. Pedigree registers for pigeons were as carefully 

 kept as for human families or for race-horses. In the course 

 of several milleniums the diversified methods of breeding in 

 different parts of the earth resulted in an amazing multitude 

 of races and varieties. 



One of the most striking races of pigeons is the well known 

 peacock pigeon which has a tail similar to that of a turkey 

 with 30 to 40 long radially arranged feathers, while the 

 other pigeons have 12, as a rule. Other pigeons are marked 

 by a bunch of neck feathers which form a kind of wig ; others 

 by an odd transformation of the beak and of the feet, or by 

 peculiar and very striking cutaneous outgrowths on the 

 head, or by a very large maw. Very strange are the pecul- 

 iar habits acquired by some pigeons, as those of the turtle 

 dove, the drum pigeons with their musical tendencies, the 

 carrier pigeon with its geographical instinct, the tumbler 

 pigeon, which has the habit of dropping down from mid-air 

 as though dead. The shape, size, color-patterns and habits 

 of these different pigeons vary much more than those of 

 the wild birds. Also their internal organs exhibit striking 

 variations. Even the bony skeleton shows marked differ- 

 ences, for instance the number and shape of the ribs vary 

 widely (Fig. 1). 



It was formerly believed that the different domesticated 

 races originated from different wild types. Darwin, how- 

 ever, definitely demonstrated that they come from a single 

 wild type: the blue rock pigeon (Columba Livid). This 

 huge number of variations has been possible in the course of 

 only a few thousand years. Reflect then how much change 

 may have occurred during the entire existence of life on the 

 earth ! 



