首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
In A short story by Ian McEwan, Reflections of a Kept Ape, a woman takes a pet chimpanzee as her lover. Although truth is often
In A short story by Ian McEwan, Reflections of a Kept Ape, a woman takes a pet chimpanzee as her lover. Although truth is often
admin
2017-03-15
82
问题
In A short story by Ian McEwan, Reflections of a Kept Ape, a woman takes a pet chimpanzee as her lover. Although truth is often stranger than fiction, a study published this week by scientists in America demonstrates that both can be pretty odd. The research concludes that humans and chimpanzees interbred after the two species first separated, before eventually going their different ways some 5.4 million years ago. Humans are thus much more recently related to their closest relatives than was previously thought. The researchers, led by David Reich of the Broad Institute of Harvard and the Massachusetts Institute of Technology, examined the genetic record of humans and chimpanzees. The sequencing of the human genome was completed in 2001 whereas that of the chimpanzee genome was finished last autumn. The two genomes are alike, differing by only 1.2% over the course of some 3 billion pairs of the genetic "letters" in which the language of genes is written. In fact, almost a third of the shared genes (each of which is several thousand letters long) are identical in the two species.
Instead of looking at average genetic differences, though, Dr. Reich and his colleagues used the complete sequences to reveal the evolutionary history of the genomes. Scientists have long suspected that some regions of the human (and chimpanzee) genome must be older than others—that some sections trace their origins far back to the common ancestral population that gave rise to humans and chimps.
Dr. Reich and his colleagues examined these common sequences, mindful of the assumption that genes steadily collect mutations as time goes by. They aligned sections of the human and chimpanzee genomes and identified how much they diverged. At different genes, humans share a common genetic ancestor with chimpanzees at different times. By studying more than 31,000 bits of the genome and measuring how closely humans are related to chimpanzees in different places, the scientists were able to study how quickly the species became different from each other. The results were published online this week in Nature.
The team found that it took at least hundreds of thousands of years and, perhaps, 4 million years for human and chimpanzee ancestors to stop interbreeding after they began to be differentiated. Humans and chimpanzees were interbreeding for all this time, before finally separating no more than 6.3 million years ago and probably less than 5.4 million years ago. This is more recent than was thought. Moreover, the argument that the two species were interbreeding over such a long time is, to say the least, controversial.
Most interesting was what the scientists discovered about the X chromosome in humans and chimpanzees. The X is one of two chromosomes that determine a person’s (or a chimp’s) sex. Females carry two copies of the X chromosome while males carry one X and one Y chromosome. The progeny of interbreeding start with a big evolutionary disadvantage. It is thought that if human and chimp ancestors initially became separate species and then started to interbreed, then the hybrid males produced tended to be infertile. (No one knows exactly why males are more affected than females, just that they are in groups ranging from mammals to insects.) A viable hybrid population could only be created if the fertile females mated back to one of the ancestral populations.
The scientists found that human and chimpanzee X chromosomes are relatively similar. Indeed, their differences are roughly some 1.2 million years younger than the average of all the non-sex chromosomes. This lends weight to the theory that a viable hybrid population was sustained by interbreeding over a long time.
Further evidence could come from the fossil record. Fossil finds are notoriously difficult to classify—people disagree on which physiological features are important; and each new find represents a class of one. The Toumai skull, found in Chad in 2001 and thought to be the earliest hominid, is between 6 million and 7.4 million years old. However, Dr. Reich points out, if humans and chimpanzees had undergone an initial separation at this time, it could account for why the skull has human-like features, including a relatively flat face without a protruding snout. The interbreeding came after this time. The researchers, along with other scientists across the world, are now working to sequence the complete genome of other close relatives to humans, including gorillas and orangutans. Primate evolution could yet reveal plenty more oddities.
What do you know about the X chromosome in humans and chimpanzees?
选项
答案
Genders can be determined by X chromosome. The ones found in human bodies are akin to those in chimpanzees, which can be followed by the conclusion that the two species interbred very early.
解析
转载请注明原文地址:https://kaotiyun.com/show/23SO777K
本试题收录于:
NAETI高级口译笔试题库外语翻译证书(NAETI)分类
0
NAETI高级口译笔试
外语翻译证书(NAETI)
相关试题推荐
Although"namingrights"haveproliferatedinAmericanhighereducationforthepastseveraldecades,thephenomenonhasrecentl
Although"namingrights"haveproliferatedinAmericanhighereducationforthepastseveraldecades,thephenomenonhasrecentl
Althoughsalmonmaytravelhundredsofmilesfromwheretheywerespawned,theywillultimatelyreturntheretolayeggs.
AlthoughtherearemanyskillfulBraillereaders,thousandsofotherblindpeoplefinditdifficulttolearnthatsystemTheyar
下面你将听到一段有关中美贸易关系的讲话。在冷战结束后的新形势下,两国要不要及如何发展双边关系,是中美两国面临的重大课题。“永久正常贸易关系”的通过表明,在美国,支持发展中美关系的力量占了上风,美国政府、国会、工商企业界和公众的主流都支持以建设性的
本次会议是信息社会世界峰会的首次政府间筹备会议,既要处理程序性问题,又要处理实质性问题。开好筹备会,是峰会取得成功的重要保证。中国代表团愿就峰会筹备工作谈以下几点看法://一、要高度重视知识和人才问题。在未来信息社会中,知识和技能是促进经济发展的
年轻男性用酒精或者毒品来寻求刺激,或者他们认为这是一种让自己更受欢迎的方式。而年轻女性用香烟、毒品或者烈酒来让自己感觉更快乐、缓解压力或者减肥。
创新犹如竹笋。竹笋要在地底下生长许多年,然后像幼苗一样把头一抬,飞速窜高。
随机试题
下列描述化脓性汗腺炎筻堡的是
关税按差别待遇分为最惠国关税、协定关税、特惠关税、普通关税、进出口关税。
甲有限责任公司(以下简称“甲公司”)因不能清偿到期债务,被债权人乙公司申请破产。2011年7月1日,人民法院裁定受理该破产案件,并指定丙会计师事务所担任破产管理人。经查:(1)甲公司应付A公司2009年9月18日到期货款1800万元。2010年9月
毛某于2002年11月5日就其自行研制的一项新的技术方案提出了发明专利申请,该申请于2004年6月6日公布,并于2005年9月16日被公告授予专利权。甲公司在未获得毛某同意的情况下,从2004年8月17日开始使用毛某的技术方案。毛某于2005年3月24日得
某旅行社对所在地的旅游行政处理决定不服,应当向()申请行政复议。
高等教育目的是衡量和评价高等教育实施效果的根本依据和标准。()
材料一:近年来,中央政府不断出台政策措施发展农村电子商务,浙江省也相继出台了一系列文件,为农村电商发展提供了强有力的政策支撑。目前,全省农村电商已形成遍布县、镇、村的网络服务体系,农村网络消费比重正在迅速提升。截至2015年8月,全省已建成4491个服务点
将图形大小设置为1。
在名称为Forml的窗体上画一个文本框,其名称为Textl,初始内容为空白;然后再画三个单选按钮,其名称分别为OPl、OP2和OP3,标题分别为北京、西安和杭州,编写适当的事件过程。程序运行后,如果选择单选按钮OPl,则在文本框中显示”颐和园”;如果选择单
AustralianminingentrepreneurClivePalmeronTuesdayunveiledblueprintsforTitanicII,amodernreplicaofthedoomedocean
最新回复
(
0
)