DWA: Well then, what explanations have been seriously considered for these rather obvious apparent perturbations?

Most likely mutations and natural selection.

DWA: ----Besides meteor impacts and random environmental disasters?

Those provide additional environmental opportunities, but nothing happens without imperfect replicators.

DWA: More important, how could we be sure that the handy explanations are covering the whole waterfront?

We can't. Does that mean we insert whatever ad hoc explanation you find satisfying?

I said: Capricious supernatural meddlers are not within the reach of science and need not be considered when one is trying to understand the history of life from a scientific point of view.

DWA: But possibly something "supernatural", like the planet Uranus eventually became known to astronomers?

I don't think astronomers ever thought that Uranus was supernatural. Do you have any serious evidence for that, or is it just something you would have suggested when anomalies were noted in the orbit of another planet?

DWA: That is, unknown but mysteriously influencing Neptune's orbit, although not known.

Gee, I think Uranus was discovered around sixty five years before Neptune, so that was indeed some mystery.

DWA: I don't embrace the arbitrary conceptual division between natural and "supernatural", so you are seeming to project something on me.

No, I am being pretty accurate in describing your willingness to accept the role of djinns, pixies and other invisible entities as explanations for what we don't already understand.

DWA: In brief: Higher intelligences in the universe can be entirely natural.

You mean it can cause so many random events that you can't tell it apart from a natural cause?

DWA: Summary: I am not presuming to know the unknown, just allowing by inference that there is higher intelligence around, by geometric analogy, that could have been interested in progress of life on Earth.