Meaning of "such, also, the biochemistry of human reproduction"?

Question

The number of years for which each particle has existed is so great that each has been part of countless billions of other objects, no doubt some of them organisms, before it was part of us. And of such an order is the number of particles needed to make up a human being — such, also, the biochemistry of human reproduction — that huge numbers of the particles that constitute each one of us have almost certainly belonged to other people.

Ultimate Questions, Bryan Magee

Could you explain to me the meaning of the text between two dashs? I am so confused about it!

Answer 1

It helps to look at what the sentence means without the confusing phrase.

"And of such an order is the number of particles needed to make up a human being that huge numbers of the particles that constitute us have almost certainly belonged to other people."

Still, this sentence is difficult to parse, so we can rearrange the sub-clauses to make the sentence more direct. For example:

The number of particles needed to make up a human being is of such an order that huge numbers of the particles that constitute us have almost certainly belonged to other people.

Basically, this sentence says that there are so many particles in a human being that it is likely many of those particles used to "belong" to someone else. In other words, most of the atoms/molecules in your or my body were once part of some other person. This understanding brings us to the phrase separated by dashes: "such, also, the biochemistry of human reproduction."

In the context of the whole sentence, we can deduce that this phrase means that the biochemistry of human reproduction also contributes to the likelihood that many particles that make up each human being once belonged to another person.

Hope this helps!