Tamed by Alice Roberts

Author:Alice Roberts
Language: eng
Format: epub
Publisher: Random House

Which came first?

We can speculate about where the first commercial, directly genetically modified chickens will emerge. But we’ve been indirectly editing the chicken genome for centuries – where and when did that all start? The answer provides us with the solution to an enduring question that has left our best philosophers completely and utterly stumped. A riddle that addles the mind and draws one into a downward spiral with insanity seemingly the only end point.

Which came first? The chicken or the egg.

And here’s the thing. Evolutionary biologists have an answer for this question. Because, before the chicken, there was the junglefowl – and that laid eggs too. And so did its ancestors, all the way back to the dinosaurs, and still further back in time. Eggs, clearly, came first.

With that epic question answered, we still need to pin down the actual origin of chickens. In the 1990s, researchers seemed pretty sure that all chickens came from a single origin, that the ancestral species was the red junglefowl (as Darwin had, once again, rightly predicted), and that domestication had occurred in a discrete area of south or south-east Asia. The genetic diversity of modern chickens is highest across that region, and much lower in China, Europe and Africa. Some researchers have suggested that the chicken homeland was, very specifically, the Indus Valley, 4,000 to 4,500 years ago (2000 to 2500 BCE), during the Bronze Age. References to ‘the bird of Meluhha’ in cuneiform tablets from Mesopotamia, dating to 2000 BCE, could relate to chickens – Meluhha itself is thought to be an ancient name for the Indus Valley. Others, though, have favoured an origin further east. Today, several distinct subspecies of red junglefowl scratch around in forests stretching throughout south and south-east Asia, from India, Sri Lanka and Bangladesh, to Thailand, Myanmar, Vietnam, Indonesia and southern China.

Doesn’t this sound like a familiar story? We know what comes next. As more information came in from wider genetic studies, the theory of chicken origins was rewritten – as one which involved diverse geographic centres of origin, across south and south-east Asia. But that impression of multiple origins is also compatible with a single origin – perhaps across a relatively wide area – followed by dispersal and extensive interbreeding with wild species along the way. Modern chicken genomes contain strands of ancestry woven in through interbreeding with closely related birds including other subspecies of red junglefowl, as well as different species such as the grey junglefowl and Ceylon junglefowl.

In 2014, a piece of research published by Chinese geneticists really put the cat among the pigeons, or the fox among the chickens, for want of a better metaphor. They articulated an astonishing claim – that chickens had been domesticated by 8,000 years ago on the North China Plain. It was so out of kilter with the rest of chicken science – and feathers flew. Most researchers remained sceptical, however, for several reasons. Firstly, the climate of the North China Plain 10,000 years ago was decidedly unsuitable for tropical junglefowl – the accepted wild progenitors of chickens.

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