Posted: Jun 16, 2011 10:27 pm
by Calilasseia
Heh, every time you breed your pets, evolution is happening. Because genes are being shuffled, and variation is being disseminated across generations. Sometimes, that variation is significant. See the Double Tail mutation in Betta splendens for an example, or for that matter just about every colour and finnage variation extant in aquarium guppies, mollies, platies and swordtails. None of those were "designed". What happened in every instance, was that the mutation showed up in breeding stock, and aquarists decided to preserve the mutation in question for aesthetic reasons. Basically, aquarium livebearers nowadays are effectively the result of over 60 years of selection of the prettiest, though how "prettiest" was defined depended upon the arbitrary whim of the aquarists involved. Personally, I think balloon mollies look hideous, but someone must have liked them enough for them to end up in the aquarium trade.

But the point remains that in all instances, what happened was the following:

[1] A mutation appeared in breeding stock that happened to attract the attention of the aquarist breeding the fishes;

[2] The aquarist breeding the fishes selected the mutant to breed from (just as nature selects which individuals in a population are going to breed and which aren't);

[3] The mutation was thus fixed in that particular line of inheritance.

In the case of the Double Tail mutation in Betta splendens (another fish that has exhibited a wide range of colour and finnage mutants that aquarists have selectively bred and fixed), the history of this is well known. It first appeared in breeding stocks in the 1970s, and was fixed in breeding stocks by aquarists who liked the look of Double Tail Bettas. Indeed, the mutation has been traced to a single gene, that exhibits classic Mendelian single-factor recessive inheritance. The Double Tail mutation has been known to aquarists interested in Bettas for 35 years, and consequently, aquarists have known how to combine the Double Tail trait with a variety of colours. I've even seen, in one of my tropical fish magazines, a photo of a "melano black" Double Tail male, which is especially difficult to produce because all melano black females are infertile, so you have to engage in a little ingenuity to combine those two traits. But, it's possible, and I have the magazine photo establishing this.

The funny part of all this being of course, that creationists think evolution couldn't happen just because they need it not to happen in order to preserve their adherence to their masturbation fantasy of a doctrine, yet the aquarium trade effectively uses Darwinian principles to bring new finnage and colour forms to market.