Should first introductory paragraph explicitly state the subject of the paper?

I am trying to write an introduction for a scientific paper. I am not sure, when I am announcing my subject, should I write that this is the subject, or just mention it without annoucing it outright?

This is very confusing so here's an example.

a. Man was always interested by aliens. This paper discusses the possibility of alien life.

b.Man was always interested by aliens. Currently, scientific discoveries are shedding light on whether it exists.

Which phrasing is better? Is the first one too blunt?