Early Canid Domestication: The Farm Fox Experiment

Early Canid Domestication: The Farm Fox Experiment

p. 49

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1. Differences between domesticated foxes and farmed or wild foxes

Development in early life:

The domesticated foxes have more time to become incorporated into a human social environment compared to the non-domesticated ones; earlier sexual maturity or retarded growth of somatic characters.

Appearance:

Domesticated foxes had changes in the foxes’ coat color, floppy ears and rolled tails which are similar to those in some breeds of dog that wild foxes do not have; shorter tails and legs and with underbites or overbites.

Biochemical mechanisms:

Selection for domestication gives rises to changes in plasma levels of corticosteroids influencing the timing of the postnatal development of certain physiological and hormonal mechanisms.

Reproduction:

1. In the breeding experiment, they found that among the domesticated foxes of both sexes, cranial height and width tended to be smaller, and snouts tended to be shorter and wider, than those of a control group of farmed foxes.
2. The mating season has lengthened. Some females breed out of season, in November–December or April–May, and a few of them have mated twice a year.

1. How these differences support Morey’s and/or Belyaev’s theories?

Development in early life:

The responding time change in behavior supports Belyaev’s theory. Also, in some cases the changes in timing when compared with sexual maturity of 8 month in the wild, resemble pedomorphosis which might support Morey’s theory.

Appearance:

That the novel traits such as a loss of pigment in certain areas of the body causing a star-shaped pattern which began to appear in the eighth to tenth selected generations as well as shorter tails and legs which appeared after 15 to 20 generations support Belyaev’s theory since those foxes with novel traits were all tame (behavior selection) after generations’ domestication.

Biochemical mechanisms:

The changes in certain physiological and hormonal mechanisms are the basis of the formation of social behavior which could support Belyaev’s theory.

Reproduction:

1. The changes in skulls seem to support Morey’s theory even foxes were selected only for behavior.
2. The reproductive traits have changed in a correlated manner since wild foxes are seasonal breeders mating once a year, which could support Belyaev’s theory.

1. Questions that are not answered by these findings

Development in early life:

1. It is not reliable for only presenting the average number of the colony to state a fact, let alone the base number which in this case is the number of domesticated foxes is not big enough. So will the standard deviation of the responding time is small enough to support the results?
2. It only “resembles” pedomorphosis and in fact they studied the skulls only of adult foxes so that whether any of these changes are pedomorphic still cannot be judged.

Appearance:

1. In figure 3 it is stated that “Belyaev’s hypothesis predicted that a similar mutation he called Star, seen occasionally in farmed foxes, would occur with increasing frequency in foxes selected for tamability”, however, the article does not present relative data to confirm this “increasing frequency” hypothesis.
2. The novel traits are still fairly rare, so what about the other majority domesticated foxes’ traits which are not clarified by the author and are they same with non-domesticated ones? If not, there are no enough proofs in the article; if yes, it contradicts Belyaev’s belief that “selection for behavior implied selection for physiological characteristics”.

Hence, here comes a question based on number 1 and 2: will it remains the same situation of such low prevalence of novel traits, which is hard to prove the behavior selection’s effect on physical changes even though after forty years there are between 70 and 80 percent of the foxes bred for tameness being members of the human-friendly “domesticated elite”?