I'm due to give birth soon, and would like to know why are humans so unfortunate to experience such a painful labour as opposed to other animals? Surely this is an evolutionary flaw, why have we kept it?

also why are our young so hepless and dependent?
and last question how did maternal instinct, and bond evolve?

Hi Laura,

Great questions! My understanding (happy to be corrected by those that have experienced this!) is that, unfortunately, the very 'basis' of humanness (a large brain relative to body mass, influencing sociality, consciousness etc.) is a harsh compromise between that large brain and the ability to stand and walk upright (which frees the upper limbs for more complex actions and grants other 'benefits') .

The large brain is likely to have been a result of a confluence of an increase in higher protein in the diet (meat intake - moving from vegetarian to omnivore diet) and an increase in dexterity (tool use).

It is likely that as early hominids moved from an arboreal existence to a bipedal existence, due to a drying climate between 5-7 million years ago (mya) in the East African Rift Valley, there were a variety of environmental pressures that selected for increases in bipedality, leading to knock on effects in subsistence utilisation and foraging (maybe dietary or foraging changes) and then, possibly, tool usage. There doesn't appear to be too many large scale morphological changes from the early hominids, such as Ororin at c. 5.5mya, through the gracile Australopithicines to the early Homo species, where an increase in tool use and meat consumption (Homo rudolfensis, perhaps at c. 1.8mya!?) started a positive feedback loop of increasing brain size.

As brain sizes increase for our distant ancestors, there is an increased limitation on the ability of the female pelvic girdle (which has changed shape and size from that of our ancestor to accommodate upright walking) to pass the skull of the child, until such a point is reached that there is a definitive limit to what the female human can feasibly pass through the pelvic girdle, which is, essentially, where we are now.

The benefits of bipedality (in evolutionary terms), as well as the benefits of a larger brain (and all the complexity that comes with that!) are the trade off with the pain of childbirth (and the very real threat of death that many women have (and still do in places) had to face before the advent of modern medicine). So, no flaw, just a compromise! Had we maintained a more quadrapedal stance, then childbirth would have been 'easier' i.e. more comparable with our primate relatives but without the 'benefits' of bipedality and large brains, which make us what we are.

The dependency of our children is again a compromise between our large brains and the amount of development that can be undertaken within the womb before the skull becomes too large to be passed through the pelvic girdle. 'Ideally', human children would be gestated for longer than 9 months within the female to make them more capable at birth but the skull would be so huge it simply wouldn't be able to be born!

Maternal instinct and bonding is common to all primates but is, perhaps, more highly developed within humans as our offspring are, relatively, more helpless than our common relatives (chimpanzees and gorillas) at the same age.

I hope this very quick skip through human evolution provides some answers but it is, obviously, only an incredibly brief and incomplete elucidation on the complexities of human childbirth. If you have specific questions based on the above, please don't hesitate to ask and we'll do our best to answer them

In short, human children are born at an earlier stage in their development than the young of most other mammals, which is why they are so helpless; and the reason is that the big brain makes the skull too big to make it through childbirth if the reached the same level of maturity that, say, a newborn horse has.