For choosing an audience it is important to think the characteristics of the people who would be interested on knowing about the theme, in this case Cloning Humans.
For talking in favor on cloning:
- Biological researchers and students could be a great audience, thus their daily work is based on knowing about new technologies.
- Rich people interested on having copies on themselves, would be also and excellent target.
On the other hand is the essay is written to criticize Cloning Humans maybe
- Human Rights defenders would be interested in reading the article as well as conservative doctors.
Choosing will depend on what you choose on your essay; an then its success would consists on writing what your audience does not know and would be interested on knowing.