Scientists have found that modern-day people are about 10% smaller and shorter than their hunter-gatherer forebears.
Most of the decline in physical size has happened in the past 10,000 years, and has been accompanied by a 10% decline in brain size.
The research reverses the popular belief that humans have grown progressively taller and larger.
"When modern humans, Homo sapiens, first appeared around 200,000 years ago they were tall and muscular," said Dr Marta Lahr, co-director of Cambridge University's Leverhulme Centre for Human Evolutionary Studies.
"The fossil evidence for the next 190,000 years is patchy, but shows that humans remained tall and robust until about 10,000 years ago when many populations show reduced stature and brain size. It is a striking change. We can see that humans have continually evolved but in body size it is not until the last 10,000 years that they have changed substantially, so the question is why this should have happened." He added.
One idea is that the decline in stature is linked to agriculture, which began about 9,000 years ago and is perhaps the greatest change in lifestyle humans have experienced.
Amanda Mummert, an anthropologist at Emory University in Atlanta, Georgia, suggests that "the impact of agriculture, accompanied by increasing population density and a rise in infectious disease, was observed to decreasestature in populations from across the entire globe - and regardless of the temporal period during which agriculture was adopted - including in Europe, Africa, the Middle East, Asia, South America and North America".
However, other researchers are less certain about the role of agriculture. Even if agriculture were the explanation for the change in stature, it would not clarify why human brain size has also decreased.


据英国《星期日泰晤士报》6月12日报道，科学家发现，与依靠捕猎和采集为生的祖先相比，现代人类的身材缩小了大约10%。
身材缩小的现象主要出现在过去1万年中，而且人类脑容量也同期减少了10%。

这一研究成果改变了先前流行的看法。人们原以为人类的身材一直都朝着越来越高大的方向进化。
英国剑桥大学莱弗休姆人类进化研究中心副主任玛尔塔•拉尔说："当现代人类，即智人，首次在20万年前出现时，他们都身材高大、肌肉发达。"

"之后19万年的化石证据并不太多，但这些化石显示，人类在此期间依然身材高大、体格健壮。到了大约1万年前左右，许多人类种群的身材和脑容量都缩小了。这一变化非常显著。我们可以看出人类一直处于进化当中，但就身材而言，直至最近1万年才发生了巨大变化，所以问题就在于为什么会出现这种现象。"


有一种说法认为缩小的身材与农业有关。人类大约在9000年前开始从事农业生产，这或许是人类在生活方式上经历过的最大改变。


美国埃默里大学的人类学家阿蔓达•穆默特认为："农业的影响，再加上人口密度的增加与传染病的增多，导致世界各地的人类种群都出现身材缩小的情况，包括欧洲、非洲、中东、亚洲、南美和北美。"




不过，也有科学家对这一观点持怀疑态度。而且即使农业真的可以用来解释人类身材的变化，它仍然无法解释为什么人的脑容量同样缩小了。

• physical [´fizikəl] a.物质的；有形的 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• belief [bi´li:f] n.相信；信仰，信条 (初中英语单词)
• striking [´straikiŋ] a.显著的，明显的 (初中英语单词)
• agriculture [´ægrikʌltʃə] n.农业；农事 (初中英语单词)
• decrease [di´kri:s, ´di:kri:s] v.&n.减少；减退 (初中英语单词)
• explanation [,eksplə´neiʃən] n.解释；说明；辩解 (初中英语单词)
• cambridge [´keimbridʒ] n.剑桥 (高中英语单词)
• continually [kən´tinjuəli] ad.不断地，频繁地 (高中英语单词)
• georgia [´dʒɔ:dʒjə] n.乔治亚 (高中英语单词)
• infectious [in´fekʃəs] a.传染，传染(性)的 (高中英语单词)
• regardless [ri´gɑ:dləs] a.不留心的；不关心的 (高中英语单词)
• fossil [´fɔsəl] n.老顽固 a.化石的 (英语四级单词)
• stature [´stætʃə] n.身高；身材 (英语四级单词)
• atlanta [ət´læntə] n.亚特兰大 (英语四级单词)
• robust [rəu´bʌst] a.强建的；茁壮的 (英语六级单词)
• substantially [səb´stænʃəli] ad.大体上；本质上 (英语六级单词)
• impact [´impækt] n.影响，作用；冲击 (英语六级单词)
• density [´densiti] n.浓(稠)密；密度 (英语六级单词)