Macfarlane guessed that the fact that water had to be boiled, together with the stomach-purifying properties of tea meant that the breast milk provided by mothers was healthier than it had ever been.

【翻译】麦克法兰猜想，水必须煮沸再加上茶净化胃的特点，这一事实意味着母亲提供的母乳比以往任何东西都更加有助健康。

【分析】这个句子确实有点复杂。分析如下：

1. Macfarlane （主语）guessed （谓语）that...（宾语从句）

2. the fact （主语）that water had to be boiled, together with the stomach-purifying properties of tea （主语的同位语） meant （谓语）that...（宾语从句）

划线部分是the fact 的同位语从句，与the fact 共同作宾语从句的主语。

3. the breast milk （主语）provided by mothers （定语）was healthier（表语） than it had ever been.（比较状语从句）

在最后这个宾语从句中，含有一个than 引导的比较状语从句。

The lame child lagged far behind.

【翻译】那个跛脚的孩子远远落在后面。

 Many theorists believe the ideal boss should lead from behind.

【翻译】许多理论家认为，理想的老板应该在幕后领导。

以上两个behind 都是方位副词，意为“后面；后边”。

the prevalence of tea  茶的流行

an extraordinary coincidence of dates 日期离奇的巧合

以上两个词组，按照of 介词短语作定语翻译即可。