【英语时差8，16】亲吻表亲

 Fans of classic movies will remember the famous dueling¹ 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 zooms² in to reveal the boy's diseased, inbred features.  Such images have contributed to the taboo³ against marriage between first cousins. Geneticists explain that since closely related persons are more likely to harbor identical genetic⁴ 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 previously⁵ 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 random⁶ partners due to the wider variety of genetic mutations. But in small, isolated⁷ populations where inbreeding is common, there's a greater chance that related partners carry the same mutations.

But 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.

1 dueling   

n. 决斗, 抗争(=duelling) 动词duel的现在分词形式

参考例句：

• More light-hearted But somewhat puzzled, Vladimir prepared to meet Eugene on the dueling ground. 弗拉基米尔心里轻松了一些，但仍感到有些困惑，在这种心情下，他准备去决斗场地迎战叶甫盖尼。 来自英汉 - 翻译样例 - 文学
• They had been dueling for hours and finally called a draw. 他们一直决斗了数小时，最后打成平局。

2 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

3 taboo   

n.禁忌，禁止接近，禁止使用；adj.禁忌的；v.禁忌，禁制，禁止

参考例句：

• The rude words are taboo in ordinary conversation.这些粗野的字眼在日常谈话中是禁忌的。
• Is there a taboo against sex before marriage in your society?在你们的社会里，婚前的性行为犯禁吗？

4 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。

5 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。

6 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。

7 isolated   

adj.与世隔绝的

参考例句：

• His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
• Patients with the disease should be isolated. 这种病的患者应予以隔离。