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Study finds American heads are getting bigger

The study found evidence that the average height from the base to the top of the skull in white men has increased by 0.3 inches.

It may sound a trifle bizarre, but white Americans' heads are changing rapidly, claims a new study.

According to forensic anthropologists at the University of Tennessee in Knoxville, heads of Americans are getting bigger in size and their faces are becoming longer and narrower since the 19th century.

In just 150 years, the volume of an average skull has grown roughly by the size of a tennis ball.

Researcher Dr. Richard Jantz said, "The surprising thing is the skull size increase has not been documented in modern Americans."

“We might have suspected that, that was happening but this documents it ... The shape of the skull has also changed rather dramatically. In fact, shape change has been more dramatic than size change.”

Though the mechanism behind the changing head shapes is ambiguous, experts theorize it may be attributed to evolution or lifestyle factors.

1,500skull examined
The researchers examined around 1,500 skulls that dated from the mid-1800s through the 1980s.

The analysis revealed that the average height from the base to the top of the skull in white men has increased by 0.3 inches. The skull size has grown by 200 cubic centimeters which is equivalent to the volume of tennis ball.

In women, the increases are seven millimeters and 180 cubic centimeters respectively.

Since the late 1800’s the skull height has gone up by 6.8 percent compared to body height which has increased by 5.6 percent. Meanwhile, femur length has only escalated by about 2 percent.

Though the overall heightening of the body has recently decelerated, the study found the skull height has continued to change.

The researchers said that skull shape in Europe has also altered considerably, but the change perceived in the US is drastic.

Plausible reason
Though the mechanism behind the changing head shapes is ambiguous, experts theorize it may be attributed to evolution or lifestyle factors.

Lee Jantz, coordinator of UT's Forensic Anthropology Center, said, "The varieties of changes that have swept American life make determining an exact cause an endlessly complicated proposition."

"It likely results from modified growth patterns because of better nutrition, lower infant and maternal mortality, less physical work and a breakdown of former ethnic barriers to marriage. Which of these is paramount we do not know."

Early maturation
The study also found that the Americans population is maturing earlier. They found evidence that the bone structure of the skull called the spheno-occipital synchondrosis that used to close at around age 20 is now fusing at age 14 years in girls and 16 in boys.

Researchers suggest childhood obesity which is known to affect hormones may be responsible for altering the timing of growth and maturation.

Richard Jantz stated, "This might affect skull shape by changing the hormonal environment, which in turn could affect timing of growth and maturation. We know it has an effect on the long bones by increasing muscle attachment areas, increasing arthritis at certain joints, especially the knee, and increasing the weight bearing capacity.”

The research was presented April 14, 2012 at the annual meeting of the American Association of Physical Anthropologists in Portland.