Sunday, May 29, 2011

So what is a chicken anyway???

Ok, so I might have given it away in my first post, The Red Jungle Fowl is ancestral to the chicken. But that is only half the story, quite literally. And just what is a Jungle Fowl?

A Jungle Fowl is a type of pheasant, Phasianidae Family, including four living species which occur in India, Sri Lanka, Southeast Asia and Indonesia. (Wikipedia) These are the Red Jungle Fowl, Gallus gallus or Rooster rooster :-), the Grey Jungle fowl, Gallus sonneratii, the Sri Lanka Jungle Fowl, Gallus lafayetii, which is more politically correct than Ceylon Jungle Fowl, though I still like the old name better, and the most aberrant of the four, the Green Jungle Fowl, Gallus varius, of Java and other islands. The Green is particularly interesting because it is a littoral feeder, frequents shorelines, and has the ability of extended flight over open ocean to reach small islands in it's range.
                                          [Courtesy of Wildlife Images]


The other Jungle Fowl, I assume, are like the typical  Ring-necked Pheasant, Phasianus colchicus, capable of limited flight only. In fact, I have observed chickens, the aforementioned barnyard bantams, fly in an identical manner; an explosive takeoff followed by a leveling off 'flap and glide' mode which can cover a considerable distance. Fascinating.

But most chickens don't fly, do they? Size is a major factor here, small chickens can get airborne much more easily than large breeds.

So, getting back to the chicken, it has been generally assumed that the Red Jungle Fowl is the sole ancestor of the fowl, being that it is the only Jungle Fowl genetically compatible, and being very close in appearance and habit. That another species could be involved has been until recently pretty much overlooked, harking back to Charles Darwin in The Variation of Animals and Plants under Domestication 2nd ed. 1875. He doubted that another parent species (of the more atypical breeds of chicken) could have formerly existed and then become extinct:
"But even if it be admitted that G. bankiva (Red Jungle Fowl) is the parent of the Game breed, yet it may be urged that other wild species have been the parents of the other domestic breeds; and that these species still exist, though unknown, in some country, or have become extinct. The extinction, however, of several species of fowls, is an improbable hypothesis, seeing that the four known species have not become extinct in the most ancient and thickly peopled regions of the East. There is in fact, not one other kind of domesticated bird, of which the wild parent-form is unknown, that is become extinct."
 This last sentence is a little confusing. He ends the paragraph:
"From these several considerations we must look to the present metropolis of the genus, namely, to the south-eastern parts of Asia, for the discovery of species which were formerly domesticated, but are now unknown in the wild state; and the most experienced ornithologists do not consider it probable that such species will be discovered." (Chapter 1. VII. Fowls)
However, he does admit by the end of the passage:
"Finally, we have not such good evidence with fowls as with pigeons, of all the breeds having descended from one primitive stock...... In the case of pigeons, I have shown that purely-bred birds of every race and the crossed offspring of distinct races frequently resemble, or revert to, the wild rock-pigeon in general colour and in each characteristic mark. With fowls we have facts of a similar nature, but less strongly pronounced....."

So here is where I break with Darwin and state plainly that the chicken is indeed a two-species hybrid. Furthermore, the 'other' parent species is also indeed extinct. What Darwin did not consider was the possibility of an island bound Jungle Fowl. Let me explain.

There is a very distinctive class of breeds known collectively as Asiatic Games. These include the Japanese Shamo, Indian Aseel and others characterized by large size, usually a pea comb, upright carriage and a coarse heavy browed head. They are often very tall.
                                  This is a Shamo belonging to a friend of mine.

These are definitely not typical Jungle Fowl. The difficulty in analyzing such a bird is that they are hybrids, not the original pure species, but I have managed to do so.

All breeds worldwide fall along a continuum from mostly Red Jungle Fowl to mostly this other 'Malayoid' type after the better known Malay breed from England.

An obviously flightless bird like this could only have evolved on an island free of mammalian predators. Yet it had to be closely allied to the Red Jungle Fowl to have preserved a compatible genome under geographical isolation.

The most likely scenario was this. The bird was discovered, many thousands of years ago, proved easy to tame and rear. Remember island birds tend to lose their fear of man. It was taken to the mainland where hybridization took place with wild Red Jungle Fowl. I know the original Malayoid was nowhere near as large as the present day Asiatics making crossing a possibility. Meanwhile, the original population on the island of origin would have become rapidly extinct, as usually happens after man discovers any vulnerable species.

I'll explain how a domestic hybrid can be broken down and studies in my next post. Promise.

2 comments:

  1. The scenario you lay out certainly makes sense. I'm looking forward to hearing more from you. Cool blog.

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  2. Thank you Tai Haku. I appreciate the enthusiasm.

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