Animal breeding / by A.L. Hagedoorn.

  • Arend Lourens Hagedoorn
Date:
[1939]
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal breeding / by A.L. Hagedoorn. Source: Wellcome Collection.

    81/410 page 51
    Domestication 51 GeofFroy St. Hilaire in Paris founded the Jardin d'Acclimata¬ tion in Paris in the middle of last century. It was proposed to produce numerous useful new domestic animals and cultivated plants by breeding suitable wild species under domestication for a number of generations. As far as animals are concerned, this object has been completely defeated, and no new animal has been added to the list as the result of these experiments. We now know why this experiment was bound to fail. Domestic animals differ from wild species in their genotype, in their inherited constitution, so that we have to have material which varies in genotype before we can change it by selec¬ tion. The only cases I know in which domestic animals have been produced from wild species have been two very similar cases of the production of domestic breeds of rats in our own cross¬ breeding experiments with those animals. I will describe those experiments in detail. We have bred the black rat {Epimys rattus) in cages for several generations without ever being able to get one tame. The same can be said for the Alexandrine species {Epimys alexandrims and E. tectorum). In our cross-breeding experiments we made some complicated hybrids, by crossing rattus to hybrids between alex- andrinum and tectorum. From these hybrids a large second genera¬ tion was raised, which was extremely variable. Many novel characters were found in those rats, such as waltzing, yellow colour, silvering, white tail-tips. A strain of yellow rats was raised for some generations in cages, and by a process of partly unconscious selection, by the fact that some pairs were easier to breed in relatively small cages than others and were more easily tamed, we finally produced a strain of tame yellow rats, a real domestic animal. Exactly the same thing happened in Cali¬ fornia, when we tried breeding the Javanese and the Sumatra field rats [Epimys diardii) in cages. In neither case did we succeed in taming the animals; they were as wild and intractable after four generations of cage breeding as before. At the same time, however, we raised some hybrids between the two strains. These hybrids were as wild as the rest, but they produced a very variable second generation. In this generation we found some albinos, and we also produced some waltzers, of two genotypically different kinds. Just as with the house rats, in the end we owned a strain of perfectly tame albino waltzing rats,
    digitised image 1
    digitised image 2
    digitised image 3