It's sort of like their family mem-bers. And in fact the number of genes they share in common is so large. And that is almost that they share a common ancestor. It's like their fourth cousins.
The friends were most alike when it came to their sense of smell but the study suggests that we could be drawn to people with similar traits because it helps us to survive.
If you are the first person that has a mutation and you don’t have any friends， you need surround yourself with other people who also have that trait. This is not just the case that people with the best trait， it’s the people we have similar genes so they are friends.
When it comes to our immunities though， the friends'genes were more different than that of the strangers. The scientists say this trend could also give us an evolutionary edge though because if your friends can fight different diseases than you；you are less likely to spread infections. It gives a new meaning perhaps to being their bio-friends.
译文：
在选择朋友时，我们的选择其实大部分是由基因决定的。和陌生人相比，我们和朋友在遗传学上更加相似。
主题转向讲述好朋友之间故事的90年代情景喜剧《老友记》。剧中两位主角有血缘关系，但如果这些人在现实生活中也是朋友的话，他们在生物学上的亲近关系相当于表亲。加利福尼亚大学研究人员分析了2000人左右的基因变异，同时，将没有血缘关系的朋友和没有血缘关系的陌生人比较。他们发现，朋友比陌生人平均多出0.1%的共同DNA，数据虽小，意义却很大。
这有点像是亲属关系。实际上，他们拥有的相同基因数量很大，几乎相当于他们拥有同一个祖先，互为第四代表亲。
朋友之间拥有相似的嗅觉。研究表明，我们容易接近拥有相似特质的人，因为这有助于我们生存。
如果你是第一个拥有一种突变的人，而且你没有朋友，那么你身边需要相同特质的人。不是说身边要有最好特质的人，而是要拥有相似的基因，才能成为朋友。
和陌生人相比，朋友之间的免疫性更加不同。但科学家说，这个趋势可以为我们的进化增加优势，因为如果你的朋友们比你更能抵抗各种疾病，那么你传播传染病的机率就会小很多。也许这能为“生物学朋友”增加新的意义。
单词解析Word analysis
1. gene[d?in]n.基因，遗传因子
例句：As we all know， we are the product of our genes.
如我们所知，我们是由基因产生的。
2. bunch[b?n(t)?]n.群；串；束
例句：A bunch of red roses drip their golden scent.
一束红玫瑰花散发出浓郁的芳香。
3. anaIyze['?n?，la?z]v.分析
例句：We should learn to analyze the essentials of complicated questions.
我们应该学会分析复杂问题的本质。
4. compare[k?m'pe?]v.比较
例句：Compare this new TV set with the old one， you will see which is better.
将这台新电视机与旧电视机一比，你就会看出哪一台更好一些。
5. fraction['fr?k?(?)n]n.部分；碎片；片段
例句：Their economy is still a fraction of ours.
他们的经济仍然是我们的一部分。
6. trait[tre?t； tre?]n.特性；特点；品质
例句：One of his less attractive traits is criticizing his wife in public.
他有个不大讨人喜欢的特点，就是爱当众责备妻子。
7. trend[trend]n.趋向；趋势；走向
例句：The general trend of history is unalterable.
历史发展的总趋势是不可改变的。
8. spread[spred]v.传播；散布
例句：The disease was spread in the small town.
这种疾病曾在这个小镇传播蔓延过。
语法知识点Grammar points
1. It appears that when it comes to choosing our friends， much of our choice depends on genes.
“It appears that……”为常用句型，表示“看起来……；好像……”；“when it comes to sth.”为固定句型，表示“说到……；涉及到……”；“depend on”为固定搭配，表示“依赖；取决于”。
2. It's a small fraction that makes a big difference.
“It is……that”为强调句型，此句中强调部分为“a small fraction”；“make a difference”为固定搭配，表示“有影响；起作用”。
3. Researchers from the University of California have analyzed gene variation in around 2000 people， comparing pairs of unrelated friends with pairs of unrelated strangers.
“have+动词过去分词analyzed”表示现在完成时；“comparing pairs……”做伴随状语；“compare with”为固定搭配，表示“相比较”。
4. The friends were most alike when it came to their sense of smell but the study suggests that we could be drawn to people with similar traits because it helps us to survive.
suggest后面是that引导的宾语从句；because引导的是原因状语从句；“be drawn to”为常用搭配，表示“被……吸引”；“help sb.（to）do sth.”为固定搭配，表示“帮助某人做某事”。