英语听力文摘 English Digest 330、近亲禁猎区

Kissing Cousins
近亲之吻

Fans of classic movies will remember the famous dueling banjos scene in Deliverance, the story of four city friends who take an ill-fated boating trip down a backwoods Georgia river. As the friends set out, one of the friends challenges a local boy with a banjo to see who can play faster. At the end of the song, the camera zooms¹ in to reveal the boy’s diseased, inbred features.

Such images have contributed to the taboo against marriage between first cousins. Geneticists explain that since closely related persons are more likely to harbor identical genetic² mutations, their children have a greater chance of being born with defects.

But such risks might be overstated. According to one study, children from first cousin marriages are only 1.7 to 2.8 percent more likely to be born with serious birth defects than children of conventional marriages. Although the risk is still significant, it is lower than previously³ thought.

Prolonged interbreeding in any species can eventually lead to serious birth defects. Harmful genetic mutations are less likely to appear in large populations where individuals reproduce with random⁴ partners due to the wider variety of genetic mutations. But in small, isolated populations where inbreeding is common, there’s a greater chance that related partners carry the same mutations.

However, harmful effects are more common in groups with a history of interbreeding over several generations. First cousins that are not from such groups run only a slightly greater risk of producing children with birth defects than non-related couples. Although such risks should not be ignored, first cousin marriage is not necessarily a recipe for genetic disaster.

经典影片《激流四勇士》的粉丝可能还记得出名的五弦琴决斗场面吧！《激流四勇士》讲述的是四个都市朋友乘着独木舟沿着未开垦的乔治亚河冒险，一路上状况不断。在旅程之初，一个朋友挑战一个当地男孩，比赛谁弹五弦琴更快。曲终，镜头推向男孩，揭示男孩因近亲交配，身体不健全的事实。

表亲结婚这样的禁忌导致了这样的后果。遗传学者解释近亲更可能携带相同基因突变信息，他们的孩子先天缺陷的风险更大。

但是，这一风险似乎被夸大了。据一项研究显示，表亲婚后的孩子比非近亲婚后孩子先天有严重缺陷的几率仅高出1.7%至2.8%。尽管风险依然存在，但是没之前预想的严重。

长期来看，任何物种间的异血缘繁殖终会导致严重的先天缺陷。人口多的地方，个体间随机繁衍，恶性基因突变几率降低很多。反之，在人口小且封闭的地方，近亲交配很普遍，有血缘的夫妻携带相同基因突变的几率更大。

但是，恶性先天缺陷常见于家族多代异血缘交配。表亲生的孩子患先天缺陷的风险略高于无血缘夫妻生的孩子。虽然这样的风险不容忽视，但是表亲结婚并非注定基因灾难。

set out:出发

mutation：突变

contribute to：归因于

harbor：怀有
 

 

1 zooms   

n.嗡嗡声( zoom的名词复数 )；隆隆声；（车辆等）疾驰的声音；变焦

参考例句：

• A sneeze zooms out of your mouth at over 600 m.p.h. 从你口中打出的喷嚏速度可达每小时600里。 来自互联网
• When the camera zooms in, the whole world watches out. 当镜头对准（汶川），全世界都在关注。 来自互联网

2 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

3 previously   

adv.以前，先前（地）

参考例句：

• The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
• Let me digress for a moment and explain what had happened previously.让我岔开一会儿，解释原先发生了什么。

4 random   

adj.随机的；任意的；n.偶然的(或随便的)行动

参考例句：

• The list is arranged in a random order.名单排列不分先后。
• On random inspection the meat was found to be bad.经抽查，发现肉变质了。