The Origin of the Chicken

Photograph of a chicken. Click to see larger version. From PLOS article cited in blog post.

Where and when were chickens domesticated?

From whence the humble chicken? Gallus gallus is a domesticated chicken-like bird (thus, the name “chicken”) that originates in southeast Asia. Ever since Darwin we’ve known that the chicken originated in southeast Asia, although the exact details of which one or more of several possible jungle fowls is the primal form has been debated. The idea that more than one wild species contributed to the early chicken has been on the table for a long time, though perhaps not as long as the chickens themselves have been on the table.

Notice the yellow legs on this chicken. If you pluck out the feathers, you’ll notice that the skin is yellow as well. But if you go find, say, a crow, and pluck its feathers, it will be grayish in color. Or maybe black, I don’t know, it’s been a while since I’ve defeathered a crow. The point is, that some birds are yellow, some are not.

ResearchBlogging.orgThere is a gene that is expressed in certain tissues that produces an enzyme that cleaves the carotenoid molecules that provide the yellow color. If there is no functional copy of this gene (if the individual is homozygotic for the broken version) then this cleaving does not happen, and you get a yellow bird (depending on other factors we shall ignore).

In short, new research confirms as previously thought that the red jungle fowl (Gallus gallus) is ancestral to the modern chicken, as Darwin suspected. But this research also suggests that another bird, the grey jungle fowl (Gallus sonneratii) also contributed to the chicken’s genome, providing the yellow color we see on this chicken’s legs.

Recent research on chicken origins

The research, reported in PLoS Genetics, gives us two results. One is the first characterization of the process of pigmentation mentioned above, and the second is a new family tree for this bird.

Many bird species possess yellow skin and legs whereas other species have white or black skin color. Yellow or white skin is due to the presence or absence of carotenoids. The genetic basis underlying this diversity is unknown. Domestic chickens with yellow skin are homozygous for a recessive allele, and white skinned chickens carry the dominant allele. As a result, chickens represent an ideal model for analyzing genetic mechanism responsible for skin color variation. In this study we demonstrate that yellow skin is caused by regulatory mutation(s) that inhibit expression of the beta-carotene dioxygenase 2 (BCDO2) enzyme in skin, but not in other tissues. Because BCDO2 cleaves colorful carotenoids into colorless apocarotenoids, a reduction in expression of this gene produces yellow skin. This study also provides the first conclusive evidence of a hybrid origin of the domestic chicken. It has been generally assumed that the red junglefowl is the sole ancestor of the domestic chicken. A phylogenetic analysis, however, demonstrates that though the white skin allele originates from the red junglefowl, the yellow skin allele originates from a different species, most likely the grey junglefowl. This result significantly advances our understanding of chicken domestication.

Here is the phylogenetic tree that the authors of this paper present:
i-a782d8d10ab087febef2b5b4a719fe02-chicken_tree.jpg

Click here for a much larger image (84kb)

Did Darwin Get It Wrong?

Every time some new research comes along that clarifies or even merely puts a finer point on something Darwin wrote about, somebody has to come along and ask the question “Did Darwin get it wrong?” as though him getting something wrong would disqualify the rest of his contributions to biology and allow us to return to believing that flies are spontaneously generated in mud. Or was that frogs. Well, whatever. In this case, Science Daily heads their report on this research with the title “Darwin Was Wrong About Wild Origin Of The Chicken, New Research Shows.” Let’s have a look at what Darwin said and see how wrong he was.

Darwin addressed the two major theories of his time, regarding chickens. One is a multiregional theory, much like the now discredited version of human evolution, where each kind of chicken was domesticated from a different wild form. The other is that all descended from one ancestor, Gallus gallus bankiva, also known as Gallus bankiva.

Darwin uses chickens in a big way in developing his ideas about evolution. Chickens were perhaps as important as pigeons for examining breed characteristics. Therefore, he wrote quite a bit about chickens. In the end, he favored the single origin hypothesis, but he also describes the primordial species of his choosing … the red jungle fowl … as much more diverse in character than it is generally characterized today…

… Gallus bankiva, has a much wider geographical range than the three previous species; … This species varies considerably in the wild state. Mr. Blyth informs me that the specimens, both male and female, brought from near the Himalaya, are rather paler coloured than those from other parts of India; whilst those from the Malay peninsula and Java are brighter coloured than the Indian birds. I have seen specimens from these countries, and the difference of tint in the hackles was conspicuous. The Malayan hens were a shade redder on the breast and neck than the Indian hens. The Malayan males generally had a red ear-lappet, instead of a white one as in India; but Mr. Blyth has seen one Indian specimen without the white ear-lappet. The legs are leaden blue in the Indian, whereas they show some tendency to be yellowish in the Malayan and Javan specimens. In the former Mr. Blyth finds the tarsus remarkably variable in length. According to Temminck20 the Timor specimens differ as a local race from that of Java. These several wild varieties have not as yet been ranked as distinct species; if they should, as is not unlikely, be hereafter thus ranked, the circumstance would be quite immaterial as far as the parentage and differences of our domestic breeds are concerned. The wild G. bankiva agrees most closely with the blackbreasted red Game-breed, in colouring and in all other respects, except in being smaller, and in the tail being carried more horizontally. But the manner in which the tail is carried is highly variable in many of our breeds,…(Darwin 1868:233)

What we see here (my emphasis added) is evidence that skin color varied across different populations of this species.

The study at hand asserts:

On the basis of observed character differences and cross-breeding experiments, Darwin concluded that domestic chickens were derived solely from the red junglefowl, though this was later challenged by Hutt [1], who stated that as many as four different species of junglefowls may have contributed to chicken domestication. Molecular studies of mtDNA and retroviral insertions have supported Darwin’s view. A study that analyzed both repeat nuclear elements and mitochondrial sequences found evidence that grey and Ceylon junglefowls may hybridize with domestic chickens, but did not provide evidence that these two species have contributed to chicken domestication. To date, no studies have compared gene sequences associated with a specific phenotype found in domestic chickens across numerous wild junglefowls and domestic breeds.

We searched for the causal mutation … This analysis revealed a surprisingly high sequence diversity between the two groups (0.81%), well above the genome average for chicken (~0.5%) [15] and approaching the sequence divergence between chimpanzee and human (1.2%). We therefore included three other species of junglefowls in the sequence comparison: grey (G. sonneratii), Ceylon (G. lafayetii), and green (G. varius) junglefowls. This step was also motivated by the fact that grey and Ceylon junglefowls have red or yellowish legs which implies deposition of carotenoids and a Y/Y genotype…

In contrast, mtDNA sequences from the same samples showed the expected pattern in which domestic chickens cluster with red junglefowl within a clade well separated from other junglefowls

The grey and red jungle fowl have, at present, disjunct ranges, but that may be a product of recent ecological changes, including human alterations of habitats. Also, in the early days of chicken domestication, there is no reason to suspect that a single origin would be followed by immediate isolation from wild forms, and in fact, all the available evidence including that reported here suggests the contrary.

I think the truth of the matter is that Darwin did not really get the origin of the chicken wrong … he had it substantially right. Rather, Darwin had a better idea of variation in the wild forms than we may appreciate today, and he leaned a bit more towards a simpler history at the start than we tend to today. That’s not bad considering that all of the modern theory about origins of domesticated forms post dates, and often derives from, Darwin.

In other words, Newton understood gravity, so today we can design an airplane. But if Newton designed and airplane that did not fly, would that mean that he got gravity wrong?

I think not.


(More on Darwin here)

Darwin, C. R. 1868. The variation of animals and plants under domestication. London: John Murray. First edition, first issue. Volume 1.

Eriksson, J., Larson, G., Gunnarsson, U., Bed’hom, B., Tixier-Boichard, M., Strömstedt, L., Wright, D., Jungerius, A., Vereijken, A., Randi, E., Jensen, P., Andersson, L., Georges, M. (2008). Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken. PLoS Genetics, 4(2), e1000010. DOI: 10.1371/journal.pgen.1000010

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Other posts of interest:

Also of interest: In Search of Sungudogo: A novel of adventure and mystery, which is also an alternative history of the Skeptics Movement.

Comments

  1. #1 Larry Ayers
    February 29, 2008

    Nice summary, Greg! Have you ever seen a jungle fowl? They are quite the impressive birds!

  2. #2 Greg Laden
    February 29, 2008

    Certainly not in the wild! I don’t recall having seen one in a zoo either.

  3. #3 postdiluvian
    February 29, 2008

    Isn’t “from whence” redundant?

  4. #4 Larry Ayers
    February 29, 2008

    Rural chicken fanciers sometimes keep jungle fowl. Some years ago when I was living in rural Knox County I was helping a young boy with a 4H woodworking project. The boy’s mother was a commercial dog-breeder and also raised chickens. She had one jungle cock but had to keep it fenced away from other fowl. She told me “That rooster will kill any other chicken it sees!”

    It was an impressive bird, standing about three feet tall, and it looked to be ready to take on all intruders. It probably wasn’t a pure specimen of the ancient oriental chickens, but it was a lot closer than your avarage Rhode Island Red!

  5. #5 Greg Laden
    February 29, 2008

    postdiluvian: It works in English. If we followed pure grammatical logic in English, no one would ever be able to return to his or her respective seat, whence the lobby, following intermission. So, technically, it is redundant, but language is language and the greatest of authors have had their characters, chickens, etc. come from a whence. Your objection would be totally valid in the 13th century, though.

    Larry: Wow. I would have figured a jugnle fowl was much smaller than that. Are you sure it wasn’t a goose suffering an identity crisis? Of course, eastern Tennessee has all kinds of stuff like that, I guess.

  6. #6 postdilulvian
    February 29, 2008

    I googled “from whence” and it turns out you’re right. Apparently it’s been used by Dickens, Twain, and the King James Bible. I feel so out of touch.

  7. #7 Alan Kellogg
    March 1, 2008

    The San Diego Zoo has red-legged jungle fowl running loose on the grounds. The story goes that the first specimens were imported for the Panama Exposition of 1914 and allowed to run loose on exhibition grounds in Balboa Park. When the San Diego Zoological Society was established in 1916 the surviving birds and their descendants were relocated to zoo grounds, though canine depredations weren’t ended until fencing was finally in place, and the stray dog problem in the area brought under control.

  8. #8 Whodunnit
    March 1, 2008

    One of the parks in Malm, Sweden also has wild (or semi-wild) fowl running about. These are quite small though, only about a foot high.

    It also have peacocks.

  9. #9 Greg Laden
    March 1, 2008

    postdilulvian: I feel your pain, man. Ever since the printing press it has been impossible to keep up.

    Alan: Interesting. I’ve been to the SD zoo. This is probably why I have this nagging feeling I’ve seen j. fowl before.

  10. #10 stewart
    March 1, 2008

    There are also jungle fowl in Hawaii, brought by the Polynesians, I think. Go along the North Shore of Oahu.

  11. #11 Greg Laden
    March 1, 2008

    Go along the North Shore of Oahu.

    That would be nice. It is probably warmer than the 12 degrees F we have right now….

  12. #12 Richard Parker
    March 1, 2008

    Thanks for the update. I have a webpage on chicken origins at http://www.coconutstudio.com/Chickens.htm.
    In my Philippines small town, chicken fights are a regular Sunday event, and the local chickens are selected for their fighting ability rather than their meat.
    You’d be hard-pressed to differentiate a jungle fowl and a fighting cock, or a feral chicken. My helper’s family used to go to the Agusan Marsh in North Mindanao to snare wild jungle fowl that they would crossbreed with their own stock.

  13. #13 BENCAULK
    April 28, 2009

    help american

  14. #14 uswa
    July 6, 2009

    im commenting this cause i look like a chicken ma real name is uswa

  15. #15 u no
    January 30, 2010

    danm chickins i hate them i love chicks

  16. #16 Gaby
    March 3, 2010

    I love chickens too and this is a great post.. :)
    Backyard Chicken

  17. #17 Boaby
    September 13, 2010

    Weeeeeeeeeeeee

  18. #18 Harry
    December 24, 2010

    That is an excellent depiction of a chicken indeed!

  19. #19 Ryan
    February 19, 2011

    They have fighting chicken in Asian countries. I think they are very similar to your jungle fowls. They use fighting chicken for small gambling games. Those are some fearsome creatures that can poke your eye out in an instant.

  20. #20 Kabir
    April 7, 2011

    Very nice and consise:- Would it be correct to say that all modern day chicken originated from ” GALLUS GALLUS” OR the correct word would be “GALLUS GALLUS DOMESTICOUS” which of these two would be an accurately describe the Ancestor of Chicken?

  21. #21 brittany
    June 8, 2011

    thats buce

  22. #22 John
    June 28, 2011

    this is very interesting
    not

  23. #23 elsayed magdy
    August 6, 2011

    i looking for chiken farm to rent close to milano

  24. #24 elsayed magdy
    August 6, 2011

    i looking for chiken farm to rent close to milano

  25. #25 Joanna Grammon
    May 21, 2012

    I grew up in the lower Yakima Valley, and was given a small flock of banty chickens. They looked like the depictions of Dutch banty stock, which in turn were imported red jungle fowl from Indonesia. My flock were ‘free-range’ and thus were introduced to a fighting cock rooster, a runaway from the nearby Filipino farmer. This ‘jungle fowl’ joined my banty flock and before long, our Irish Setter decided they were no longer domesticated banty chickens, which he had left unmolested, but wild and ergo fair game. He began killing my chickens. I even tied a dead chicken around his neck, a supposed cure, but it didn’t work. After that, he was tied on a long leash to the backyard tree. I don’t know what happened to the flock when we moved and left them with the new owners. They certainly were beautiful. long-tailed jungle fowl.

  26. #26 ken
    philippines
    January 22, 2014

    i have one of a jungle fowl.. it is a blue legged and its a wild one if u want to see it come visit my website or either chat me on my face book

  27. #27 Dean Snow
    Penn State
    March 24, 2014

    Hi Greg
    Coming as I do from a family that made a fortune in poultry I’m happy to see both your piece on chickens and clear evidence that you are alive, well, and productive.

  28. #28 Greg Laden
    March 24, 2014

    Ha. Still alive!

    I taught Intro to Archaeology last semester and your name came up a couple of times, Dean.