American heads are getting larger although it's unclear why that is happening, forensic anthropologists at the University of Tennessee, Knoxville, said.
Examining 1,500 skulls dating back to the mid-1800s through the mid-1980s, the researchers found U.S. skulls have become larger, taller and narrower as seen from the front and faces have become significantly narrower and higher, a UT release reported Wednesday.
The researchers said it cannot be determined whether the changes are primarily due to evolution or lifestyle changes.
"The varieties of changes that have swept American life make determining an exact cause an endlessly complicated proposition," researcher Lee Jantz said.
"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."
Skull height has increased 6.8 percent since the late 1800s, while body height has increased 5.6 percent and femur length has only increased about 2 percent, the anthropologists said.
The research only assessed Americans of European ancestry because they provided the largest sample sizes to work with, researcher Richard Jantz said.
Changes in skeletal structure are taking place in many parts of the world, he said, but tend to be less studied although research has uncovered shifts in skull shape in Europe.
Still, he said, those changes are not as dramatic as those seen in the United States. (UPI)
<관련 한글 기사>
미국인들의 머리가 점점 커지는 이유?
미국인들의 머리가 시간이 지나면서 점점 커지면서 아래위로 길어진다는 연구결과가 발표되었다.
테네시 대학의 인류학자들은 1800년대 중반부터 1980년대 중반까지의 미국인 두개골 1,500개를 조사하여 이러한 결과를 얻었다고 말했다.
그러나 이와 같은 변화가 진화에 따른 것인지 생활습관의 변화 때문인지는 아직 밝혀지지 않았다고 한다.
연구진에 따르면 1800년대 후반과 비교하면 키는 5.6% 커지고 대퇴골은 2% 길어진 반면, 두개골의 길이는 6.8%나 더 길어졌다고 한다.
연구에 참여한 리처드 잔츠는 두개골 변화에 대한 연구는 유럽에서도 진행되었으나 미국처럼 ‘극적인(dramatic)’ 변화는 찾아볼 수 없었다고 말했다.