First, you seem to think cognition is all or nothing, that one either has it or he doesn't. That is not true. Many animals have minimal levels of cognitive brain function.
Well I was throwing the word around loosely but nah I am fine with levels of cognition. I mostly lean towards thinking it was a progression, but I won’t say I’m 100% on it. Because they say Neanderthals were just as smart as us, but then some argue that they weren’t. Well nobody is arguing that they were more intelligent than us yet their brains were 20% larger. So this makes the progression of intelligence based on brain size argument a little suspect for me. They also say that human brain volume has a poor correlation with intelligence. So these things make me have doubts about how much weight to put on the other hominids having lower intelligence due to a smaller brain. We can’t study a non-human hominid brain they are all decomposed for thousands of years all we have is an empty skull to look at.
The skulls of the earliest hominids we find show evidence of increased cognitive power. They are nowhere close to homo sapiens in brain power.
How much can we know from an empty skull?
Patterns of things like making tools, making fire, cooking, cave paintings, etc are a better (but still vague) gage to compare intelligence levels between hominid intelligence. But even with that it’s just so far into the past, there’s such a scarcity of clues.
You also seem to have difficulty understanding the problems with having increased brainpower. Every mother can tell you that it is not easy getting a baby's head down the birth canal. So even if you are God, you cannot simply decide that the next primate to be born will have a full sized human head. The mother who tries to deliver that baby will curse your holy name. So you need a way of getting increased cognitive brainpower, while having mercy on the mothers.
But this would be a really tough situation for any species at all. Childbirth survival rates were horrible back then anyway, it isn’t like Homo sapiens were in some plush setting where it wasn’t a major problem. There are many species who stay put and don’t move around all the time not just Homo Sapiens. Ok so long infancy periods is the price you pay for having self aware cognition, so what, many species could have been given this same burden/benefit package deal.
The second trick is to allow the brain to increase in size after birth. Again, evidence shows this in our ancestors.
By ancestors do you mean infant fossils that we have of Homo Erectus and other hominids?
But in early hominids, there were enough of advantages to increased cognitive ability that natural selection favored these changes. It was a tradeoff, but it was worth it. For other primates, these changes were not worth it.
It being worth it is totally subjective though, yes it’s a tradeoff, but it makes no sense that out of millions of species it was only “Worth it” for a very select few in all of Earth’s history, and then on top of that the very few died off all except for Homo Sapiens. How could higher self aware intelligence NOT be worth it for 0.00000001% of species, but worth it for just one? “It was worth it” sounds ad hoc in order to hold onto the blind portion of evolution.
The fact that evolution started this trend of giving a boost in cognition to about a dozen different species, and they all died off except for one, and evolution never again felt the need to repeat this process, looks very guided and goal oriented. I mean we had a trend starting here! Then evolution just reverses course and pulled the plug on the cognition project? And now other species could really really use this ability because of what humans do to the world! Evolution looks more like a LINE to humanity than us blindly winning a self awareness lottery.
Also, you don't seem to recognize the resource needs of the enlarged brain. If a monkey suddenly gave birth to a monkey with a human brain, what good is that? This brain is going to require an immense amount of energy. If there is nobody around to communicate with her, if there is nobody to teach her to make a fire, make a hand axe, or organize a hunting expedition, what is she going to do with a human brain? She is going to eat like a carnivore, and add little to the community. How is she going to get all the meat she craves?
But if evolution is allowed to proceed in a slow path, with the body, brain, and available technologies all developing within a community of hominids, the result is, uh,
us!
You can’t have it both ways, you are either married to this extremely slow progression theory AND you have transitional fossils to back it up with, or evolutionary leaps happen very very fast.
How does this even work exactly, if Homo Sapiens came onto the scene at let’s say 100,000 BC then what were they in 100,100 BC? If you object and say that the transition would be WAY longer than 100 yrs, well if that is the case then we would have transitional fossils. Unless you have a lot of “Iffy” fossils that are judgment calls because they are stuck somewhere between being Homo Sapiens or being Homo Erectus for example (ie REAL transitional fossils) then how can you hold onto a very slow progression theory? But if the transition is extremely fast then that explains why you aren’t finding those fossils. BOTH situations are difficult! Yes the monkey giving birth to a human creates a problem. But what if the change was lightning fast, like 200 years? That could give us about 6 to 8 drastic generation leaps in increments (easing that problem), and a scant 200 years could also forgive no transitional fossils being found.
The hominid fossils are all drastically different.