descended from a common ancestor是一个省略了that的定语从句，修饰people.descended from的意思是传下，遗传，如：
1） His family were descended from an Indian tribe3. （他的家庭是印第安部落的后裔。）
2） Darwin concluded that men were descended from apes. （达尔文判定人由猿进化而来。）
descend1 to 的意思是屈尊，减少；转而说到
1） The firm had descended to using nude4 pictures for advertising5. （那家公司堕落到用裸照做广告。）
2）Mr. Lee then descended to the details we had to be careful about.
（李先生转而谈到了大家需要注意的细节问题。）
common是一个形容词，意思是共有些，一同的；普通的，请看例句：
1）No doubt， this is a grammatical6 mistake common to beginners in English.
（毫无疑问，这是英语新手常犯的语法错误。）
2）How could you have no idea about this common knowledge？ （对这个普一般识你如何会一无所知。）
3）They have no common interests. （他们没一同的喜好。）
3. Some people thank of a family as a mother， a father， and their children，
think of as 是一个非常常见的词组，意思是把看作，如：
1） He often thinks of himself as a genius. （他常把自己看作为天才。）
2） The Yellow River is thought of as the cradle7 of the Chinese nation. （黄河被看作为中华民族的摇篮。）
与think ofas意思相近的词组在英语中还有不少。如：
regardaslook uponas
seeasviewas
consideras
4. For others， having a family simply means having children.
本句中，having a family做主语，mean为谓语动词，having children 做宾语。mean在句中的意思是意味着。当mean作意味着讲解时，在它的后面应该跟名词或者动名词，如：
1）Accepting the job would mean moving to another city. （同意这份工作将意味着我得搬到另一个城市去。）
2）A raise in the worker's salary will mean a cut in the profit. （增加工人的薪资意味着收益的减少。）
当mean作意欲，计划讲解时，在它的后面一般跟不定式，如：
1）I didn't mean to offend you. （我无意冒犯你。）
2）I meant to give you the book yesterday， but I forgot it. （我原计划昨天把书给你的，但我忘了。）
5. Some families have long histories， while others know very little about their ancestors.
请注意while的使用方法，在本句中while是一个表示转折意味的连词，意思是然而。如：Fred gambled8 all his money away while Jane saved every penny for her son's schooling9. （弗雷德赌输了他所有些钱，而珍妮却为儿子的教育攒下每一分钱。）
while在不一样的语境中有不一样的意思，请翻译下面的句子，注意while的词义。
1）They decided10 to find a less expensive place to stay while in Paris.
（在巴黎期间，他们计划找个更实惠的地方住。）
2）He looked at his watch several times while talking to her. （在跟她交谈时，他看了几次表。）
3）One group of children are quiet， while the second group was very active.
（一组孩子非常安静，而第二组孩子很活跃。）
4）While I have sympathy for these people， I think they are guilty. （尽管我同情这类人，但我感觉他们有罪。）
5）We will succeed while we don't lose hope. （只须大家不失去期望，大家就会成功。）
6. No matter if it is young or old， large or small traditional or modern， every family has a sense of what a family is.
no matter if 连接让步状语从句，更容易见到的是用no matter whether.除去no matter whether以外，no matter wh-引导的让步状语从句还有：no matter what， no matter who， no matter whose， no matter which， no matter when， no matter where， no matter how等等。而用wh-ever引导让步从句也是十分容易见到的。请看下面的例句：
1） No matter what happens， please let me know. （无论发生啥事，请让我了解。）
2） No matter who telephones， tell him I'm out. （无论哪个来电话，告诉他我出去了。）
3） No matter how hard I tried， I couldn't succeed. （无论我多努力，我总不可以成功。）
4） No matter whether you believe it or not， it's truth. （无论你信不信，那一直事实。）
5） No matter where you go， I will follow you. （无论你去什么地方，我都跟着你。）
6） No matter which book you like you can have it. （无论你喜欢哪本书，你都可以拿去。）
7） No matter whose money it is， we can't spend it so carelessly. （无论是哪个的钱，大家都不可以如此随便地花）
上述某些句子可以用wh-ever表述如下：
1） Whatever happens， please let me know.
2） Whoever telephones， tell him I'm out.
3） However hard I tried， I couldn't succeed.
4） Wherever you go， I will follow you.
5） Whichever book you like， you can have it.
7. It is that feeling of belonging， of love and security that comes from living together， helping11 and sharing.
本句中的it代指课文前一句中的a sense of what a family is. feeling of belonging 意思为归属感。
security 是一个名词，意思是安全。
that comes from living together， helping and sharing 是定语从句，修饰that feeling of belonging， of love and security.
8. However， with the change from an agricultural to an industrial society， many nuclear families moved away from the family home in order to find work.
本句中的however是一个表示转折意味的副词，有承接上文有哪些用途，可以使这个句子和前面的句子连接得更紧密，有的接近连词。请看例句：
1） This， however， is not your fault. （但这不是你的错。）
2） I'd like to go with you， however， my hands are full. （我非常想和你一块去，可是我忙不过来。）
句中的with是一个介词，意思是伴随，请看例句：
1）With the change of the economic foundation， the superstructure has to be transformed too.
（伴随经济基础的改变，上层建筑也需要改造。）
2）With the development of science and technology， the society is changing rapidly.
（伴随科技的进步，社会在飞速地改变。）
with是一个十分常见的介词，请看下面的句子，注意with的使用方法和词意：
1）Who will go with you？ （哪个和你一块去？）
2）The teacher is very strict with us. （老师对大家非常严格。）
3）At the news we all jumped with joy. （听了这个消息，大家都开心得跳了起来。With表示缘由。）
4）He wanted to kill two birds with one stone. （他想两全其美。With意为用，以，译法可灵活。）
5）China is a country with a large population. （中国是一个有海量人口的国家。With表示有，带有）
6）He finished this work with great difficulty. （他很不容易才完成了这项工作。With引起短语作方法状语。）
7）He was sitting in a chair with his hands folded.
（他双手交叉在胸前坐在椅子上。With引导独立结构：with+名词+过去分词，做方法状语。）
8）What's wrong with you？ （你如何了？with意为就来讲）
9）With your knowledge and experience， you are sure to find a good job.
（以（凭）你的常识和经验，你一定会找到一份好工作。）
10）With all his shortcomings， he was a nice person. （尽管他有缺点，他还是个很好的人。）
句子中的in order to find work做目的状语，除去用in order to 以外，还可以用so as to，也可以把in order，so as省去，只用不定式。请看例句：
1）He decided to study harder （so as ） to catch up with the others. （他决定加紧学习好赶上其他人。）
2）He ran out in a hurry （in order） to catch the last bus. （为了赶上末班车，他匆匆向外跑去。）
