由羅納德科圖拉克
Tribune science reporter 科學記者論壇
Published August 17, 2006 發布時間2006年8月17日 One of the most intriguing mysteries of biology is why humans are the only species with a brain smart enough to ponder their own existence. 其中最有趣的奧秘生物學是為什麼人類是唯一的物種有足夠聰明的大腦去思考自己的存在。
Researchers at the University of California at Santa Cruz believe they have discovered a possible answer: a gene that has undergone powerful mutational changes in the last 5 million years that may partly account for the accelerated evolution of the human brain. 研究人員在加利福尼亞大學聖克魯斯相信他們發現了一個可能的答案：一個基因，該基因發生了突變的變化有力，在過去5百萬年，可能部分地解釋了進化的加速，人類大腦。 報告週三在網上版的英國醫學期刊的性質，科學家表示，他們不知道到底是什麼做的基因，但它是活躍在一個關鍵的時間和地點在胚胎發育時，大腦是增長最快的步伐。
"The properties of this gene are that it's turned on at about week seven of embryonic development in the same cells that help build the cerebral cortex," said David Haussler, director of the university's Center for Biomolecular Science and Engineering and a Howard Hughes Medical Institute investigator. “的性質研究該基因是，它的開啟約一周7胚胎發育在同一牢房，幫助建立大腦皮質，”戴維說豪斯勒，主管這所大學的中心生物分子科學與工程和霍華德休斯醫學研究所調查員。
"And then it's turned off at about week 19 when the process is finished. It suggests that the gene is probably involved in this process of building the cerebral cortex because it's turned on in the right place at the right time and turned off in the right place at the right time." “然後它關閉約19週時，此過程結束。提示該基因可能參與了這一進程建立大腦皮質，因為它打開了正確的地點在合適的時間和關閉的權利地點在合適的時間。“
Bruce Lahn, whose University of Chicago team reported earlier this year the discovery of two genes indicating the human brain is still evolving and perhaps becoming smarter, said the Nature report is a potentially important advance in uncovering the brain's genetic building blocks. 布魯斯拉恩，芝加哥大學的研究小組報告在今年早些時候發現的兩個基因，說明人類的大腦仍在發展中，也許變得更聰明，報告說，自然是一種潛在的重要進展，在揭示大腦的基因組成部分。
"Eventually all this information is going to come together and play a role in better human health and a better understanding of human evolution," he said. “最終，所有這些信息將走到一起，發揮作用，更好的人類健康和更好地了解人類進化的，”他說。
Haussler's group found a gene called HAR1 that appears to exist in the brains of all animals. 豪斯勒的研究小組發現的基因稱為HAR1這似乎存在於大腦的所有動物。
For most animals, from chickens to chimpanzees, the gene underwent little change for hundreds of millions of years, suggesting it performs a vital function. 對於大多數動物，從雞到黑猩猩的基因進行一些改變億萬年，這意味著它執行了重要作用。
But sometime in the last 5 to 7 million years, after the human lineage diverged from its last common ancestor with the chimpanzee, HAR1 began to change substantially. 但有時在過去5至7億年後人類血統偏離了它的最後的共同祖先與黑猩猩，HAR1開始發生重大變化。
Today, approximately 10 percent of the human HAR1 gene is different than that of the chimpanzee, Haussler said, adding that the genetic changes may contribute to the human brain becoming three times larger than that of a chimp. 今天，大約有百分之十的人HAR1基因是不同的比黑猩猩，豪斯勒說，該基因的變化可能有助於人類大腦變得大於3倍的黑猩猩。
HAR1 belongs to a newly discovered type of gene made out of RNA instead of the usual DNA. HAR1屬於一個新發現的基因類型開出的RNA而不是通常的DNA。
RNA genes are made from DNA genes, but then they go on to act as genes in their own right. RNA的基因是由從DNA基因，但隨後他們繼續充當基因在自己的權利。
One of their jobs, it is thought, is to regulate other genes. 他們的工作之一，它被認為是調節其他基因。
The HAR1 gene is active early in embryonic development when certain neurons produce a protein called reelin that guides the growth of brain cells and the formation of connections among them. 該HAR1基因在胚胎發育早期活躍在某些神經細胞產生一種蛋白質稱為指導reelin的腦細胞的生長和形成它們之間的連接。
The neurons orchestrate the layered structure of the human cerebral cortex, the brain's intelligence and command center. 神經元的層狀結構編排了人類大腦皮質，大腦的智慧和指揮中心。
After this period of rapid development, HAR1 is turned off. 經過這一時期的快速發展，HAR1是關閉的。
Scientists generally believe the complex human brain evolved over time because it provided a survival advantage to the vulnerable ancestors of humans. 科學家們普遍認為，複雜的人類大腦進化時間的推移，因為它提供了生存優勢，弱勢祖先的人類。
"Why aren't there more species that have achieved the level of intellectual capability of humans? Why doesn't everybody want a big brain?" “為什麼沒有更多的物種，已達到的智力水平能力的人？為什麼並不是每個人都希望有一個大的大腦嗎？” Haussler asked. 豪斯勒問。
"Well, the brain uses a lot of energy, about 20 percent of the energy in the body. It's definitely a costly organ to maintain from an energy perspective. I suppose if you're just out grazing on the grass all day, it's a waste of effort." “嗯，大腦使用了大量的能源，約百分之二十的能量在體內。這絕對是一個昂貴的器官，以保持從能源的角度來看。我想，如果你只是進行放牧的草地上一整天，這是一個浪費精力。“
The tiny brain of the primitive sea squirt, for example, shrinks even smaller after birth, yet it gets along in its niche very well, pumping water in one hole and out another. 這種微小的大腦的原始海鞘，例如，出生後縮小甚至更小，但它在其利基相處得很好，在一孔抽水和出另一個。
"Sea squirts have evolved a way of essentially getting rid of its brain," Haussler said. “海鞘已基本上形成了這樣的擺脫它的大腦，”豪斯勒說。
"It finds a rock, sits down on it, eats its own brain and becomes a kind of vegetable sitting on the rock, filter feeding. “發現一個石頭，坐在它，吃自己的大腦，成為一種蔬菜坐在岩石，濾食性。
"They have been very successful. They're happy. They don't need their brain," he said. “他們都非常成功。他們都很高興。他們並不需要他們的大腦，”他說。
Early humans, on the other hand, "got by by the skin of our teeth. It was our cunning that sculpted us as a species." 早期人類，另一方面，“得由我們的皮膚牙齒。這是我們狡猾的雕刻我們作為一個物種。”
To help define the role of HAR1 in brain size, neuroscientist Pierre Vanderhaeghen of the University of Brussels, an author of the Nature paper, is developing a mouse strain that lacks the HAR1 gene. 為了幫助確定的作用，HAR1腦的大小，神經科學家皮埃爾Vanderhaeghen大學布魯塞爾，一個作家的本質文件，正在開發一種缺乏的小鼠品系HAR1基因。
The purpose is to determine if the animals without the gene are born with smaller brains. 其目的是確定如果沒有這種基因的動物出生時較小的大腦。
"If they delete the gene in a mouse and the mouse has a smaller brain, then one can argue that the changes in this gene might have contributed to a larger human brain," said the U. of C.'s Lahn. “如果他們刪除該基因在鼠標和鼠標有一個較小的大腦，那麼我們可以認為，這種基因變化可能導致一個更大的人類大腦”之稱的美國的C.的拉恩。 | 
