"Conversely, breeders have crossed  highly inbred lines to get heterosis. These crosses may have qualities not seen in the original types."

Crossing highly inbred lines may or may not provide heterosis.  However, it is completely clear that heterosis has little or perhaps nothing at all to do with hybrid vigor no matter how often the claim is repeated.  In fact we really do not know what causes hybrid vigor other than knowing heterosis is not a major cause.  There are excellent examples in crosses of highly inbred lines of corn which produce offspring as puny and lacking in vigor as the parents.  In fact heterosis can be a negative as shown by the limited fertility or absence of fertility of numerous such crosses and the frequent absence or rareness of the heterogametic sex in both animals and birds from such crosses.  Even worse in some cases the F1s are reliably fertile yet the B1s are only marginally fertile. Red Siskin cock X Canary hen is such a case.

On those crosses where some benefit is seen in the F1 most of the time the benefit does not persist in subsequent generations.  This is particularly true if the benefit is increased vigor as expressed by faster growth and larger size.  Thus farmers are forced to buy brand new hybrid seed corn every spring to plant.  Planting seed saved from last years crop results in a miserable yield compared to brand new hybrid seed.  Occasionally a new trait can be introduced into a species via such crosses.  That is how the red color was put in canaries.  It is also how check markings were put into the common pigeon.  You can generally expect several generations of poorly performing stock while you are fixing such gene transfers from one species to another species.

Brother Adam's work needs to be placed in perspective of the time he did his work.  Rampant breed crosses and species crosses were all the rage when he did his work and he simply followed the lead of what was being done with all kinds of domestic critters.  In the vast majority of cases such experiments led no place.  In fact most of Brother Adam's crosses did not result in improvements.  I am not really sure any of them did.  He also followed the rule of mating the best to the best and get rid of the rest.  I suspect that is where most or perhaps all of his progress really came from.  He also benefited from a lack of back yard bee keepers so was able to establish mating apiarys where he could have some control of the drone population.  Very few of us have that advantage today.

Dick

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