What Constitutes Authorship?

Certainly, I do not completely agree to Dr. Bradley Smith's opinion saying "Without the contribution, would it still be published?"

Some project have lower intellectual/concept development and higher mechanical labour in form of performing experiments , gathering huge amounts of data, analyzing them and further refining.

Say 4 people worked on a project and pinned it down within 2 months. Now, lets take out 2 people, and ask the same question "Without their contribution, would it still be published?"
Yeah, it might be or would be, but in 5-6 months.

In that case, won't you give authorship to those 2 people?