in the image of Yahweh ...

[βαθμιαίος]

I think the second time (mating) was fairly recent (3300-3600 years ago).

18.20 Questioner: When did Yahweh act to perform the genetic changes?

Ra: I am Ra. The Yahweh group worked with those of the planet you call Mars seven five, seventy-five thousand years ago in what you would call the cloning process. There are differences, but they lie in the future of your time/space continuum and we cannot break the free will Law of Confusion.

The 2600, approximately, time was the second time — we correct ourselves — 3600, approximately, the time of attempts by those of the Orion group during this cultural complex; this was a series of encounters in which the ones called Anak were impregnated with the new genetic coding by your physical complex means so that the organisms would be larger and stronger.

24.9 Questioner: Then Yahweh, in an attempt to correct what I might call a mistake (I know you don’t want to call it that), started 3300 years ago a positive philosophy. Were the Orion and Yahweh philosophies impressed telepathically, or were there other techniques used?

Ra: I am Ra. There were two other techniques used: one by the entity no longer called Yahweh, who still felt that if it could raise up entities which were superior to the negative forces, that these superior entities could spread the Law of One. Thus this entity, “Yod-Heh-Shin-Vau-Heh,” came among your people in form according to incarnate being and mated in the normal reproductive manner of your physical complexes, thus birthing a generation of much larger beings, these beings called “Anak.”

I believe it's what's referred to in Genesis:

There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.