Last time we took an overview of the early evolution of the chicken as we know it today however this time we will take a step backwards. Chickens weren’t always chickens, at least not the way we think of and see chickens today or even a couple of centuries ago.
The humble chicken today is most probably the most numerous bird on the planet. In fact did you know there are more chickens on the planet than there are people? In 2002, the United Nations Food and Agriculture Organisation estimated that there were 19 billion living chickens in the world, with China having the largest number, followed by the US, Indonesia, and Brazil. This means that with a world population of just over 7 billion then there are almost three chickens to every person in the world at any one point in time.
This was not always the case because the chicken began its existence as a rather localised, obscure, ground dwelling pheasant of the jungles of Southeast Asia. In truth they are classed with similar birds in the taxonomic order Galliformes (commonly called gamebirds or galliforms). This ‘group’ includes – in addition to the chicken and its wild forerunner the jungle fowl – turkeys, pheasants, quail, partridges, guinea fowl, and peafowl.
Galliforms in general are adapted to life on the ground, and as result tend to be heavy in the body when compare with other birds. Whilst we don’t consider chickens to be flyers, the Galliformes are not viewed as flightless, with some capable of flight, though none of them are particularly strong flyers. In the wild most of the species in the order use this ‘half flight’ ability for the primary purpose of avoiding predators. If, whilst out walking you have ever happened upon a pheasant you will familiar with the sudden explosion of wing-flapping as the bird takes off. This is usually accompanied by a squawk and you jumping in alarm. It is a defence mechanism design to startle a potential threat or predator and usually lasts for only a few moments, but sufficiently long enough for the bird to land and gain a fair few metres of distance between itself and the threat.
It was most probably Charles Darwin who first proposed that the ‘chicken’ was the evolved from the galliforms, primarily the jungle fowl (Gallus gallus) and most probably the red jungle fowl. The red jungle fowl, which has the broadest range of the jungle fowl, most resembles the domestic chickens in appearance and behaviour. In fact, many novice and even some experienced poultry enthusiasts could mistake it for a chicken, although truly wild examples of the breed are infrequently encountered. This species is among a group of four surviving, and as many as 13 extinct pheasant-type species that are found from western India through the southern reaches of Asia and into the island chains of Indonesia and the Philippines. The birds generally dwell on the jungle floor and on the margins of grasslands that edge forested areas. The ranges of these closely related species however rarely intersect, so there is little possibility of natural hybridization between them. This indicates that man must have influenced the evolution of the chicken at the very beginning as opposed to a natural occurrence.
The other jungle fowl species have relatively small ranges and are mostly isolated. The grey jungle fowl (Gallus sonneratii), sometimes called Sonnerat’s jungle fowl, is found in the westernmost part of the overall range of jungle fowl, generally in peninsular India. It differs most strikingly from its red jungle fowl cousin in its comb—the small points and minimal serrations of the grey jungle fowl comb are clearly in contrast with the more chicken-like “single comb” of the red jungle fowl.
The remaining two jungle fowl species are isolated to some of the islands that lie within the overall range of the Gallus genus. The Sri Lankan jungle fowl (Gallus lafayetii; previously called the Ceylon jungle fowl) is found only on the island of Sri Lanka off the eastern tip of southern India, while the green or Javan jungle fowl (Gallus varius) is found on a few islands in western Indonesia, including Java and Bali.
It is understandable to see how evolutionary theory would identify the red jungle fowl as being the precursor to the chickens we see today however it is not unsurmountable to consider that the ‘chicken’ may have evolved down all the lines of jungle fowl. Even today the true roots of the Araucana are under debate with studies continuing into its true origins. The ones seen today most
certainly will be related in some way to the original jungle fowls, however there is evidence to suggest that the blue egg-laying bird that was discovered in the Northern Chile (later to be known as the Araucana) may in fact have no Asian roots at all, and may not be related to any of the four foundation species of jungle fowl.
The history of the most numerous bird on the planet may documented from domestication onwards but the actual origin and prehistory of the ‘chicken’ remains as complex a question as to which came first, it or the egg?
Next time we’ll take a step forward and investigate the history of the chicken post its early domestication. It was a time when our humble feathered friends where more associated with augury and omens than Aga and onions.