Punctuation

Here I listed some tricky sentences on which I added some commas and the other elements of punctuation. I am now editing an English-related book, so I need your viewpoints. Would you please tell me which punctuation in which sentences are not necessary/right? I don't know BE and AE differences in this field.

1. Every speech or presentation has two important parts—one is the words themselves, and the other is how to say them. (After themselves)

2. Genealogy is a branch of history. It concerns family history, rather than the national or world history studied at school. It doesn't merely involve drawing a family tree, however—tracing your family history can also result in learning about your roots and identity. (comma and em-dash around "however".)

3. Technology plays an increasingly important part on our daily lives. While many technological developments may be beneficial – in the field of medicine, for instance – there are many others whose effects are less positive. We may find examples of these in the world of work, in the home, and in the whole area of freedom and privacy. (Comma after "in the home")

4. Every day more information is collected by banks, credit card companies, consumer organizations, and so on, and who is there to keep an eye on what happens to it? (comma after "organization")

5. Historically, during man’s first half million years, the growth of the world’s population must have been exceedingly slow. It seems certain that the whole population of mankind cannot have reached much more than ten million before the Neolithic revolution resulting from the discovery of agriculture around 6000 B.C. After that, with infant mortality, famine, disease, and war, the growth rate continued to be very slow, with the population doubling itself once every thousand years. (Comma after "years" in the first sentence and comma after "disease".)