I've read a couple articles that touch on this. The current theory has been summarized as there being an evolutionary arms race between genes that benefit the child at the mother's expense and genes that preserve the mother while being somewhat detrimental to the child's fitness (but as a result beneficial to her other offspring).

In this regard, longer gestation and a larger cranium are both better for the child. But our large crania are difficult to fit through the various choke points in the birth canal, and endanger the mother's life. The result is basically gestation as long as possible and crania as large as possible to permit natural childbirth to usually be non-fatal -- but that inflection point is one where even a non-fatal childbirth is difficult and painful.

(There are also elements of the theory that relate to frequency of fertility, and why human menstrual bleeding far exceeds that of other mammals.)

Because of the external gestation, my understanding is that survival rates for marsupial offspring are lower than for mammals. As for other mammals, giving birth is difficult for them too, though we don't have a way to measure how their pain compares to ours. However, no other mammal has gone down an evolutionary pathway where its fitness depends on brain size, so no other mammal has to contend with evolutionary pressures that so directly affect the ease of birth. (Plus, bipedal mammals with upright gaits are rare, so the evolutionary pressure affecting pelvic shape are different.)

To be fair to humans, we are born at a pretty early stage also. Human babies are all but helpless at 12 months after birth and pretty helpless for another 12 months after that (and then they are still rather helpless).

A kangaroo leaves the pouch in around 8 months.

Kangaroos are marsupials, which are non-eutherian. Humans (and, indeed, most mammals we're familiar with) are eutherians. The birthing process is quite different, and so makes for a poor comparison (for one, humans don't have a pouch). A better question would be to compare human pain to other, eutherian animals who do not experience much pain in delivery (see: any nature documentary).

Humans have large heads and walk upright. These are great for many things, but not giving birth.

Ineffective because natural selection doesn’t over optimize.

EEG suggests earlier born babies can have huge merits in intelligence evolution: https://www.scientificamerican.com/article/does-a-newborn-s-...

Well, you’re not alone in wondering that. In fact it was noted in the Bible as part of God’s curse when we became “enlightened” by eating fruit from the tree of knowledge. We’ve at least known it’s harder than it should be for a very long time.

We are very effective at breeding, especially with the help of science and technology. The inefficiency of birth, if true, hardly matters.

>We are very effective at breeding, especially with the help of science and technology.

In what sense? Our production rate is substantially lower than most other animals; mothers-to-be are made weaker than other animals during the process; the threat of death in childbirth for both child/mother is hardly the lowest of other animals

We have a relatively high population now, but its hard to imagine that its due to an efficient breeding process; rather our survival rate post-birth, lifespan and our phenomenal ability to edit the environment to increase resource production to support higher populations are likely better explanations

Put a pair of rabbits in a room and a pair of humans, with all needs met. We're not even competitive

Do you mean kangaroos?

Maybe that's how they spell kangaroo somewhere. Like color and colour.