Chickens are a weird study in domestication. People have had chickens around for a REALLY long time….but nobody is really sure where they came from exactly…
It seems that red jungle fowl were hybridized with grey jungle fowl about 8000 years ago. The original strains are likely to have come from Thailand, but domestication seems to have happened independently several times in southeast Asia and China between 5400 and 5200 BC. I can’t help but imagine a Chinese Johnny Appleseed-type guy….wandering from village to village saying “if you keep some of these birds in your house, you won’t have to go hunting all the time….”
A couple thousand years later, the chicken made it to the Indus valley (around 2000 BC), which has been called the cradle of agriculture. It was this are where many of our domesticated animals were domesticated, as well as many of the hybrid grain and vegetable crops that are the progenitors of todays farming across the world. It is from the Indus valley that chickens found their way to Europe and Africa.
Now that we know where chickens came from, how have they changed? It’s been a LOOONNNGGG time, and we’ve been messing with these birds pretty aggressively. People have been VERY successful in increasing the ability of the bird to produce eggs. Jungle fowl will lay around 5-6 small eggs per year. Leghorn (the strain of white hens that are the most commercially successful chicken throughout the first world) hens will lay over 325 eggs in a year, and the eggs are much larger than the wild counterparts. That is pretty obvious, and expected.
What is interesting is that domesticated animals (all of em…not just chickens) gain some traits when being domesticated…..think about it. Domestic dogs, cats, cows, chickens, pigs…..all of them become less fearful of predators, have a less serious fear response, and show less interest in novel stimuli. All that is understandable as animals are chosen on their ability to cope in a confined, human-centric environment….but there are other things too. The one that amazes me is that domesticated animals uniformly turn more white. I don’t know why….it makes sense that domesticated animals don’t need to be as camouflaged, but why bother changing?…..also…does that mean that blondes are more evolved than the rest of us?
Domesticated chickens also use a more energy-conserving foraging strategy and are less active in fear tests, compared to jungle fowl. This means that, given a choice, they PREFER more bland food, as long as it is easier to get, where as jungle fowl will work harder to get tastier tidbits.
The more predictable environments that leghorns find themselves in have caused them to be more risk averse, and less responsive to things like food deprivation. Leghorns will act much more normally during experimental food deprivation than jungle fowl, who will spend more time searching for food, and spend more time off perches (a risky behaviour for hens in a jungle).
Maybe even more intriguingly, there are several traits that have not changed much from junglefowl….hens still flock together much the same way…the same inter-bird spaces, the same synchronization of behaviour, similar responses to predators. Both leghorns and jungle fowl imprint readily on objects as babies, and will approach that object readily later in life….but leghorns have less flexibility in this….in one experiment, they could not get used to a blue ball in the pen, where jungle fowl imprinted on it readily. Leghorn hens also show more fear of a novel environment than jungle fowl. Leghorns will adventure less, and show more agitation in unfamiliar surroundings.
Other behaviour remain important to the hen, while being unnecessary in captivity. Nest building is an important activity that hens will work hard to fulfill, as is foraging for food (interesting that leghorns will choose to eat bland, easy to get food in preference to novel foods, yet will then spent time scratching for food after they have eaten their fill), perching and dustbathing.
The fact that jungle fowl are still alive and available for study is a rather unique situation. Other domesticated farm animals do not have an ancestor to be compared to. The aurochs (cow ancestor), mouflon (sheep ancestor), and tarpan (horse ancestor) are extinct, and the wild boar that exists today is very different from the ancestor of the modern pig. As such, these species’ behaviour are not compared to the ancestral in order to try to guess what they would prefer. I think it is dangerous to look at jungle fowl and expect that laying hens will desire or prefer the same things. There is information to be gained from studying jungle fowl, but laying hens cannot be un-domesticated, and should be evaluated on their own when deciding on how to manage them, and what behavioural needs must be accounted for.
Mike the Chicken Vet