Until I read the bit about a person turning into a small bird I've been searching in diverse Sci Fi fields.
Now I'm gonna start looking in Fantasy places also!
Were they actually called 'Earthers' in the book, do you remember?
I am not sure what those left behind on Earth were actually called. I used the word to distinguish between those who stayed and those who left into space.
But if more details will help…
At the beginning of the book, when the spacer lands on Earth, it is evening and he sees a campfire so walks toward it. Sitting at the fire is a small man, that actually looks more like a dwarf or gnome. He his sitting outside his small home by the fire near a pond.
When the spacer announces himself, the little man is frightened by the stranger. Even more so when he learns the man is from the space faring humans because the law of the land is that if ever humans return to Earth, they are to be despised and destroyed. Eventually the spacer convinces the little man to help him, or at least help him find someone in authority.
This is when we learn there is no formal government on Earth. Basically, Earth is sort of ruled by one individual who has the most powerful telekinetic powers. Though, it seems this powerful person is very benevolent. Overall Earth is now very peaceful.
Here we learn that passing through the comet's tail did far more than change humans. The comet was so large that gravitational forces acted on Earth causing huge earthquakes and volcanos and completely changed Earth's landscape and killing almost the entire population of humans. Humans really have just started to repopulate the planet even after hundreds of years.
Also, this is when we learn that there are three main laws enforced by the benevolent ruler. Technology is banned from Earth and can never be allowed to exist again, a person must choose their final form by the age of 18 and never change shape again, and noe one is allowed to visit the Forbidden Place. Eventually the little man helps the spacer and introduces him to a character I think is named Manuel.
It turns out that Manuel is actually the second most powerful individual on Earth. He agrees to help the spacer and is willing to take him to meet the benevolent ruler. However, the ruler is a long way away and they will have to walk because no technology is allowed and they cannot use the spacer's craft. No problem. Manual chose being a giant as his final form. Although this is a little odd because he can shrink himself to be normal height and grow to be 40 feet tall. Not sure how he gets around the whole, 'never shape change again', thing. But I guess being the second most powerful human has its privileges.
Eventual they make it to the capital where the ruler lives. Apparently, the ruler studied up on ancient Rome because the capital is described to look much like ancient Rome and the ruler dresses in togas and robes. This is where we learn that the constant use of the ability to create objects with the mind actually impacts the environment. The ruler demonstrates the issue by creating a simple ball in his hand and when he does so, flowers in a pot next to him wilt just a little bit.
This is also when we learn about the Forbidden Place. (Not sure what it was really called). This place is the secret shared by the two most powerful humans because it seems that they obtained their great power by going to this place on earth that focuses the effects from the comet. The book describes the place as a bowl-shaped place that sounds much like the Arecibo observatory and radio telescope.
I think it is here that the conflict between the space humans and the Earthers is defined. The ruler tells the spacer that the space humans are not welcome and will not be allowed to land back on Earth. The spacer agrees to be an emissary and returns to the ship orbiting Earth to inform his superiors. Of course, his superiors have other ideas and plan to basically invade Earth now that they know what is own there. Now or protagonist has to choose sides.
He steals a shuttle to return to Earth to warn the ruler. This is when he begins training Earthers to fight against the humans in space. This is when he visits the shape changer's island to select a team that he will lead up to the ship in orbit and attempt to take the ship.
Just to reiterate from my previous post, while the Earthers do not have advanced weapons, they have their telekinetic and shape shifting abilities. During the training, he urges one of the Earthers to try and take away his stun gun. At first the Earther cannot get within a few feet of the protagonist who keeps stunning the Earther. However, the Earther figures out that he can shift from a human form, to a small bird, fly towards the protagonist evading the stun gun shots and shift back to human form as he hits the protagonist thus rendering advanced weapons rather useless.
At some point, the spacer's team ends up hiding in the Forbidden Place. While there, the protagonist realizes that he now is gaining the same psionic powers as Earth humans. This is rather terrifying because if the space humans learn they too could acquire these powers, surely, they would stop at nothing to gain them. Eventually the protagonists team wins the day and captures the orbiting ship. Can't remember how all that plays out.
The culmination of the book is when the wife of one of the main characters, who is hiding at the Forbidden Place, gives birth and the child is a mutated human that grows to adulthood in just a few days and has incredible psionic powers including telepathy. This new human takes over the planet and demands that all children be born at the Forbidden Place and the beginning of a new human race is spawned.
The super children then want to move into space and start to create space vehicles. When the super child leader asks the main character from the space humans where the best place to go in space is, the human tells him. However, the super child reads the space human’s mind and thinks he is lying. The super child misreads the human’s mind and goes to the planet with the worm-like aliens, (mentioned in my first post) by mistake. Hopefully that will be the end of the mutated humans.
Maybe the above will help.
Again, thank you.
Allan