This one is for my dad, who loves chickens. In the December 2012 edition of Heredity (Miao et al., 2012), there was an article published about the evolutionary history of chickens. It’s a good article and a good topic to learn about phylogenetic trees, too. Humans have been raising chickens for a long time–in fact, chickens were the first domesticated bird (West & Zhou, 1988)! The first archaeological evidence for humans keeping “chickens” dates back as early as 8000 years ago in China (6000 BCE), but the dates vary by geographical region worldwide. The modern scientific name for these birds is Gallus gallus domesticus. This suggests that domestic chickens as we know them are actually a subspecies of the Gallus gallus. It would be tempting to call this the “wild chicken,” but it is actually the red junglefowl.
Looks like a chicken, right? The resemblance is pretty strong. Based on similarity alone, we would probably make the assumption that this wild bird is likely to be the ancestor of chickens. But what can DNA tell us? Researchers recently took mitochondrial DNA from over 2000 different types of chickens worldwide, plus 51 red junglefowl. Remember, mitochondrial DNA (mtDNA) is inherited from the mother’s side ONLY (it is not in sperm), so we can use this to trace the matrilineal relationships among these birds. Similar efforts have been made before using mitochondrial DNA of chickens and red junglefowl, and those studies strongly suggested that the red junglefowl was the common ancestor of modern-day chickens (Bao et al., 2008; Irina, Romanov, Nikiforov, Sevastyanova, & Semyenova, 2003; Kanginakudru, Metta, Jakati, & Nagaraju, 2008; Liu et al., 2004; Masahide, Hanazono, Yamamoto, Tsudzuki, & Yasue, 2003). In that regard, this research isn’t exactly new or novel.
What made this particular paper different were a few things:
- Sample size. They tested far more birds than previous studies. They also supplemented their data set with previously-published DNA sequences to study over 4000 birds.
- The mtDNA sequencing. Previous studies used only one part of the mtDNA (the “Control Region”) while this study sequenced the entire mtDNA.
- Geographic spread. They tested chickens and red junglefowl from many locations. Once they sequenced the DNA, they asked modern software to reconstruct a phylogenetic tree of the birds.
Figure 1 shows how the different types of birds clustered together—which groups were more closely related. The red numbers are from red junglefowl. Previous work set up 7 obvious groups (A-G). Notice that each group has at least one red junglefowl in it. This suggests that chickens weren’t domesticated just once, but maybe as many as 7 times! (Possibly more—this was just based on the birds they tested).
This new research established some new groups and sort of merged the previously-established groups: A and B merged (AB), as did CD and EFG. Some groups were further subdivided: the group C was found to have a sub-group C1, for example. So now you have this sort of diagram:
And that’s just for the historical groups we already knew about! Researchers also identified some new groups. The new groups were designated H-I and W-Z. Remember, this all has to do with mitochondrial DNA—this doesn’t even apply to chicken breeds at this level! It’s easiest to imagine people doing this. Here, I’ve got this awesome bird—it lays lots of eggs and tastes great with some water and noodles—here’s a baby for you! Each time the birds get passed there’s a chance that the new family’s birds will become different. This is just a larger scale version of the same idea.
The neat thing is that you can use this information to see where chickens today are similar or different. Notice Southeast Asia is about half red (B)? That’s different than anywhere else in the world! The Pacific chickens are different, too—mostly orange (D). Across most of the rest of the world, chickens seem to be a whole lot of E1. Asia has most of the diversity. All of the mtDNA groups are found there.
This article supports the idea that chickens were first domesticated in Asia from the red junglefowl. Domestication probably happened multiple times as people caught the wild birds and kept them for food or as pets. Then, chicken farming spread out across the world from there!
What’s for dinner?
References:
Bao, Wen-bin, Shu, Jing-ting, Wang, Cun-bo, Zhang, Hong-xia, Weigend, Steffen, & Chen, Guo-hong. (2008). Investigation on Genetic Diversity and Systematic Evolution in Chinese Domestic Fowls and Red Jungle Fowls by Analyzing the mtDNA Control Region [J]. Chinese Journal of Animal and Veterinary Sciences, 11, 001.
Irina, G Moiseyeva, Romanov, Michael N, Nikiforov, Andrey A, Sevastyanova, Antonina A, & Semyenova, Serafima K. (2003). Evolutionary relationships of Red Jungle Fowl and chicken breeds. Genet. Sel. Evol, 35, 403-423.
Kanginakudru, Sriramana, Metta, Muralidhar, Jakati, RD, & Nagaraju, J. (2008). Genetic evidence from Indian red jungle fowl corroborates multiple domestication of modern day chicken. BMC Evolutionary Biology, 8(1), 174.
Liu, ZG, Lei, CZ, Luo, J, Ding, C, Chen, GH, Chang, H, . . . Xiao, XJ. (2004). Genetic variability of mtDNA sequences in Chinese native chicken breeds. ASIAN AUSTRALASIAN JOURNAL OF ANIMAL SCIENCES, 17(7), 903-909.
Masahide, Nishibori, Hanazono, Makoto, Yamamoto, Yoshio, Tsudzuki, Masaoki, & Yasue, Hiroshi. (2003). Complete nucleotide sequence of mitochondrial DNA in White Leghorn and White Plymouth Rock chickens. Animal Science Journal, 74(5), 437-439.
Miao, YW, Peng, MS, Wu, GS, Ouyang, YN, Yang, ZY, Yu, N, . . . Mitra, B. (2012). Chicken domestication: an updated perspective based on mitochondrial genomes. Heredity.
West, Barbara, & Zhou, Ben-Xiong. (1988). Did chickens go north? New evidence for domestication. Journal of Archaeological Science, 15(5), 515-533.