Because the species that can't, doesn't know how to figure out in their brains how to do those things?
Evolution occurred in all organisms, not just those of humans.
There are other organisms that don't have brains, so brains are not the only factor to consider for evolutionary changes, and in some cases, speciation occurred due to such change.
Beside that.
What intelligence are you talking about?
I am asking because intelligence among humans varied widely.
So are there a particular form of intelligence that you are referring to?
To give you an example.
Let's supposed that there are two humans. One of them is intelligent because he is a rocket scientist, while the other is a cook.
Does that mean a cook who cannot design rocket, as being "less than human" or "not human"?
And when each have children, grandchildren and so on, do they inherit their knowledge and skills through DNA?
Or are such skills and knowledge taught to them?
As Tiberius have tried to explain to you, intelligence is not good indicator of evolutionary changes, because no knowledge and no skills inherited through their genes, hence being able to built rockets or to cook chow mien or grill steak are not heritable biologically, hence such skills and knowledge have absolutely nothing to do with Evolution.
Intelligence are not good indicator of changes to biology, especially of non-human organisms.
To give another example, brown bears and polar bears are closely related to one another, are considered sister-species. Biologists, specialists in bear biology would investigate HOW, WHERE & WHEN such changes occur - the divergence of these two species.
You could resort to what many creationists resort to, and say -
- they are not different species,
- or the silly "bear will always remain bear"
- or say even more stupid thing like "Can a bear give birth to a dog"?
1 and 2 aren't explanation, just assertion without understanding the biology of two different types of bears.
And 3, is what only idiots say, because they don't understand Evolution, so they "make up" insane and impossible scenario that no biologists would consider them to be serious question.
Number 3 comes up a lot among creationists, especially like "Can cat give birth to dog?" or "Can dog give birth to cat?" Or the frequent "Can chimp give birth to a human?"
No biologists would ask this sort of question, because it is just plain ignorance and intellectually dishonest to repeat such lame and unscientific scenarios.
None of these are probable, because they don't understand Evolution. especially the "common ancestor"?
Neither humans or chimpanzees exist 7 million years ago, but some extinct species that exhibit some common physical traits of either before the divergence. So no, chimpanzees didn't and cannot give birth to human species, nor humans to chimpanzees.
This extinct species was possibly Sahelanthropus tchadensis (also known as the Toumai), which flourished during the Miocene epoch, the specimen were found in Chad. The science community haven't yet reached a decision if the Sahelanthropus is a direct common ancestor of both humans and chimpanzees, or not.