Scientist: Genetic engineering has aided new developments in many different fields.
Conclusion
Genetic engineering is not unethical. rephrase: It's okay to do genetic engineering.
Evidence
Selective breeding, as we've done with farm animals for millennia, is a crude form of genetic engineering.
Evaluate
The author is arguing both by appeal to analogy and to tradition.
She's saying, . This assumes that anything we've done for millennia couldn't be unethical.
That doesn't seem like sound logic. Slavery existed for centuries, if not millennia, and it is clearly unethical.
The other structure at play here is the argument by analogy, where we say,
Let's look at the two things and what similarities they're meant to have in common:
Picking which farm animals Manipulating the genetic you want to use for breeding codes of organisms
intended similarity 1: they're both a form of genetic engineering intended similarity 2: they're both ok (not unethical)
We might dispute either of the intended similarities. Is it really fair to say that both of these things are genetic engineering? Or is this equivocation? One of them literally means manipulating the genetic code of a living organism. The other one is talking about organizing which two things will have sex.
Is it really fair to say they're both ok? Who ever said that crude farm-based genetic engineering we've been doing for millennia is actually ethical?
Goal
The answer might deal with the missing link.
It might deal with the author's assumption that farm-breeding and genetic-code-manipulation are really relevantly similar forms of genetic engineering.
It might deal with a missing piece of the author's analogy: that farm-based selective breeding itself is ok / ethical.