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Latest Mind and Matter column in the Wall Street
Journal is the extraordinary story of modern chicken genetics.
Of all the amphibians, reptiles, birds and mammals in the world,
the most abundant species is probably the chicken. At any one time,
approximately 20 billion cocks and hens are alive on the planet
(though never for long).
Chickens owe this abundance, of course, to their place on our
table. About 90 million tons of chicken meat are consumed every
year, plus 67 million tons of eggs, compared with 110 million tons
of pork and 67 million tons of beef. Between 1970 and 2005, world
production of poultry meat more than quadrupled.
The red jungle fowl was domesticated around 4,000 years ago in
India, where it still calls cock-a-doodle-doo in tiger-infested
forests. But the triumph of the chicken is relatively recent. Until
a couple of decades ago, beef and pork outweighed poultry in the
average American diet. Fifty years ago, chicken was a scarce
delicacy in many European countries.
What accounts for the rise of cheap chicken? First, motorized
transport led to the growth of the intensive broiler industry, in
which food is brought to the birds rather than vice versa. Second,
selective breeding led to birds that were more efficient at
converting grain into meat. Remarkably, this genetic improvement
even now shows no sign of tailing off.
Ten years ago, Dr. Gerry Havenstein at North Carolina State
University did a careful study of weight gain in chickens,
comparing (under identical conditions) a modern 21st-century breed
with a 1957 breed that had been kept going. He found that, at six
weeks of age, the modern chicken was six times as heavy and had 9%
more breast meat. Of that improvement, he found, 85% came from
genetics and only 15% from better feed.
By 2001, when the study was done, a chicken reached the weight
at which it would be killed in one-third of the time and after
eating one-third of the food compared with the 1957 breed. That
represents a considerable reduction in waste and in the amount of
land devoted to growing feed per chicken.
In the decade since, there has been a consistent and linear
increase in both weight gain and food-conversion efficiency in the
broiler industry. Outside the lab, on the farm, chickens have
accelerated their daily rate of growth by about 0.89 grams per
Nothing illustrates the power of selection in breeding better
than this extraordinary change. But geneticists had expected the
improvements to plateau by now. Shouldn't all of the best genetic
combinations have been discovered? No less confounding is the fact
that this effect has not been confined to chickens: The milk yield
of dairy cattle shows similar linear improvement.
Two possible explanations for the continuing trend are that
there is a lot more hidden genetic variability in a typical genome
than scientists thought, or that brand new genetic mutations are
happening fast enough to supply fresh variability to the
Whichever explanation is true, there's every chance that chicken
growth rates may accelerate more, thanks to "genomic selection."
This means testing many different birds to hunt down what mutations
are boosting chickens' performance, using a gene chip with 60,000
single-letter DNA variants on it. You can then use that information
to predict, even before they've hatched, which chicks will grow
into successful fathers.
Many people would prefer chickens to be scratching,
free-range, in farmyards. Given that this is impractical if the 3.5
billion people who live in cities are to eat affordable chicken
meat, the genetic improvement of chickens is, on balance, good
news. It means that they are fed from ever smaller acreages of
land, leaving more for nature, and produce less waste. Nor is it
clear that their living one-third as long is any more cruel, since
they are killed either way-and they can be bred to be less