Short story about Advanced Alien Species observing rapid evolution of Humanity

Question

The basic plot of the story was:

An advanced alien species visits prehistoric earth and engages with early homo sapiens. One of these homo sapiens was, I think, the leader of the tribe visited and they're given a typical caveman name (Can't remember exactly, probably Gruk, or something along those lines) which is later amended with every descendant of this caveman.

The alien species depart and return to earth when it was in the age of feudalism, the Caveman's descendent (Greketh or whatever a stately rendition of the name Gruk would've been to match contemporary naming conventions) now a feudal lord. The alien species depart yet again, I think this time they don't intend to return, and the next stage of the story takes place after humanity has been integrated within the Empire of the advanced alien species.

Greg (descendant of previous men in story) is a high official, and is subordinate to a Galactic Queen. I think it is explained that females of the alien species are able to live 1000's of years whilst the males only have a maximum lifespan of 100 to a 200 years. As the Galactic Queen, who is now relatively old, approaches her death, she relegates more and more of her responsibilities to Greg, and by the end of the story the Galactic queen concludes the story by expressing awe at the rapid evolution and adaptability of Humans, which is significantly greater than her own or any other observed species.

Answer 1

Pyramid by Robert Abernathy. I read it in the anthology More Penguin Science Fiction.

The "caveman" is Morg:

Morg, the hunter, strode easily through the open woodland beneath fronded trees that would have seemed very strange to his great-grandfather several times removed. The same great-grandfather would also have been surprised by the parklike, orderly look of this forest, free of tangling brush and strangling vines, but to Morg it was merely normal.

The tribal leader is Morgus:

The farmer Morgus was rich. The fields worked by his numerous family and dependents stretched for miles around the big stone house that the present farmer’s grandfather had built when he first settled in that country; and members of his clan, the Morgusi, owned most of the land in these parts, so that as patriarch of the clan he was a recognized leader through all the countryside.

And the assistant is Morgu:

The door of Zilli’s office slid quietly open at her approach. In the roomy, well-lit chamber beyond, two men rose quickly to their feet from a paper-strewn desk by the great curved window that looked over the city. One of them was Antan Morgu, Zilli’s confidential secretary—a neatly barbered and manicured man of indeterminate age, dressed, as always, in conservative but expensive clothing of synthetic fabrics, and in a studiously affable expression.

The aliens are the Thagathla and the female who ends up as a high ranking official (not really a Galactic queen) is Zilli:

They were thagathla—beings six-limbed like the snig to which they were kin, but with crested heads carried erect and forelimbs that ended in clever fingers instead of the snig’s shovel-like digging paws. One of them wore the communicator which kept them in touch with their scout ship, out of sight beyond tree-grown ridges; another carried a gas gun; the remaining one, whose name was Zilli, was a junior biologist with a future. Since she was the only scientist in the landing party, Zilli was its ex officio leader.

The part where Zilli is musing over the adaptability of humans is:

In the beginning she had correctly judged the species adaptable; at the time no one could have guessed the full scope of its adaptability, the almost fantastic facility of imitation by which humans had transformed themselves successively, in a few brief centuries, into functional equivalents and supplanters of the thrin, of the zgi, and finally of the thagathla themselves. Mimicry was a trait alien to the thagathla; among humans, Zilli vaguely knew, it had subjective values ranging from flattery to mockery.