My crazy theory is this:

If there was a breeding program to create a species which would have working thumbs, a certain amount of reason, the ability to be trained and/or indoctrinated, a useful "tool' which self-corrects most injuries, etc, AND:

During those breeding trial experimentation (prototype testing), they tested larger skulls for larger brains.

The typical deliverer was a smaller framed female. They sought the females with the broadest hips. The name "broad" for female still exists today.

They sought the females who were the most fertile, like domesticated hens (because that his how females were kept, as "layers"). The words, "chick" and "bird" for female still exists, as does the verb for intercourse, "lay".

And they still had problems in delivering the BIG HEADS holding those brains.

They manipulated the soft skulls during development in the womb to help the baby deliver, elongating the pliable skull plates.

They had long heads due to this manipulation in hopes it would be a successful trait in the offspring of those with elongated skulls.

It never was successful as a trait because manipulation of fetal skull tissue does not change the genetic traits for a round, spherical, skull.

Some cultures thought to board the heads of children to maybe kick in this trait in the persons having their heads elongated. That didn't work either.