On the other other hand, of course, (primordial) dwarf humans do also exist, which are as small as, or even smaller than, Flores Hobbits, with adult human intelligence to boot.
You don't have to roll your eyes at me, thank you. I'm not an idiot.
However, extreme dwarfism is not really the same thing at all.
Some things to note:
- evolving a certain body shape and then having some individuals have dramatic abnormalities in some parts of the body to produce a different body shape is not the same process as naturally evolving that second body shape from the beginning. In particular, most people with dwarfism are of normal intelligence because their skulls are of normal size (a minority do have proportionally significantly smaller, or malformed, skulls, and they do indeed generally show reduced intellectual abilities). But there's a difference between evolving a human shape that includes a large skull (and then having a few humans have the rest of the body smaller than normla) and directly evolving a shape that includes a large skull but a small body.
Bodies tend, through evolution, to grow proportionately. Humans have already developed relatively huge skulls and brains - you're asking for something to develop an overwhelmingly incredibly (relatively speaking) huge skull and brain. And to do that at the same time as evolving for flight/gliding, which prioritises loss of weight!
And I do mean 'overwhelmingly'. The average human has a head that's about 7% of their total weight. People with the most extreme forms of non-microcephalic dwarfism may have a head around 30% of their total weight. To put it another way: chimpanzees have brains that are about 0.7% of their body weight, average humans have brains that are about 2.1% of their body weight, and you're talking about people with brains maybe 20% of their body weight. Now, brain-body ratios (with 'brain' being on a log scale) actually follow a pretty narrow band in all known animals - even humans aren't an immense deviation from that. Extreme dwarfism IS an immense deviation from that, like nothing that ordinary evolution has ever produced.
- and no, it's not as simple as saying "oh well dwarfism shows that these mutations are possible, so that's how this species evolved". Because extreme dwarfism is probably not a viable evolutionary strategy. You mention primordial dwarfism, for example - well, aside from the fact that many people with primordial dwarfism do have cognitive impairment, we also need to bear in mind that almost all people with primordial dwarfism die before they reach 30, even with modern medicine and care. Even less extreme dwarfisms are widely accompanied with serious medical conditions. Bones and spines may be deformed, nerves dangerously compressed. Small torsos can result in compression of vital body parts. And that sort of extreme mutation is often accompanied by seemingly unrelated afflictions, because when you roll the genetic dice like that all sorts of things can come up. You mention Verne Troyer, for instance - well, cartilege-hair hypoplasia like he has is also commonly associated with immunodeficiency problems and a predisposition to cancer (as well as seemingly random things like hyperextensible feet and very thin hairs). Gradually reducing size bit by bit is one thing, but the sort of extreme mutations you're talking about, that have an extreme effect on some body parts while not affecting others at all, are really unlikely to happen in just the way you want without also happening to bring about many completely undesirable traits. New species don't (at least in the overwhelming number of cases) form like that. They form from a series of evolving body forms, each of which is in its own right a positive adaptation for the environment.
- Let's remember here: even Verne Troyer cannot fly. He is still twice the length of a colugo (not counting their tails). And despite the fact that he's only twice the length of a colugo, he's a massive sixteen times the weight of a colugo
. If he stretched out his hands, he'd have a wingspan maybe something like only 2/3rds that of a giant golden-crowned flying fox... but he has more than ten times the weight.
Let's put this another way: you see the gliding flaps on the colugo? Those flaps are just about big enough to carry two thirds
of Verne Troyer's brain. (boy, this post has some strange sentences in it). Or again: if Verne Troyer's brain were the heaviest falcon in the world, it would by itself require a 1.5m wingspan. Assuming that the wings themselves had no weight! And that's not counting a skull to protect that brain, a digestive system, lungs, heart, some bone structures, some muscles to actually move those wings, and so on.
I just don't think an intelligent glider is plausible. If you really wanted a glider that could just about be scientific, I think your only option would probably to evolve it in the other direction: take a bird (with hyperminiaturised brain for flight), make it grow really big to have an increased brain size, and then somehow have it partially lose its flight while retaining its brain...