"In the 1960s fewer than 5 percent of deliveries were Cesareans and more than 40 percent involved forceps. And those numbers are related. Gawande makes a strong case that in the hands of experts, forceps are safe (according to some research, safer for mothers than Cesareans). But forceps are hard to learn to use properly – a process that can take two years. And if forceps are used by inexpert doctors, the results can be disastrous. Cesareans are easier to master. And this has led hospitals to phase out forceps and, in many cases, do C-sections instead. To discourage the inexpert from using forceps, Gawande says, “obstetrics had to discourage everyone from using them.” This change has come at a cost. Gawande notes that, as straightforward as Cesarean deliveries can be, they can go wrong. The baby can be lacerated. If the head doesn’t come free quickly, the child can asphyxiate."
"Childbirth is difficult for many reasons, she writes—among them the 19th-century switch from birthing in the upright position, which allows the pelvic girdle to expand in response to contractions, to the supine position (still common among women in the West) which often requires the use of forceps."
There are correct times and places for all tools. But comparing two interventions that both bring risk is an odd way to approach the topic.
"N of one", but I have a cousin who was mentally retarded/disabled during birth when forceps were used on his head.
Obviously I don't have proof of the cause (that would require a counterfactual birth), but he is disabled, has an abnormally oblong head, and this is the stated reason of the family (also not incontrovertible facts).
The spotted hyena is one of the most successful carnivores in Africa; yet females hyenas lack an external vaginal opening and therefore give birth through their narrow clitoris (...). During parturition, the clitoris ruptures in order to facilitate the passage of the young, and may take weeks to heal.
One can only imagine the extreme pain and difficulty involved in this; yet it's unlikely there's an evolutionary justification to be found. It's most probably an accident -- a quite unfortunate one for the female hyena.
I don’t think anyone can really say whether the testosterone or matriarchal organization came first (or co-evolved).
"Many experts now believe that rape is best understood as an act of unwanted bodily invasion that need not involve force."
So yes the male could still coerce, through emotional manipulation or threat of physical force, a female to comply without direct physical force but I don't know how applicable that is to hayenas (or most non-human animals).
No, they're not as sensitive as the clitoris (and no, I don't think we know precisely how sensitive the hyena clitoris may or may not be) but human women also give birth through tissue that is dense with nerve endings and more sensitive to both pleasure and pain than, say, that on the outer surface of your arm.
I vaguely recall a guide explaining this during a SafariLive stream
> I have a number of papers that show that women are great walkers, and in some particular tasks women are better—they don’t use as much energy, they don’t build as much heat, they can carry heavier loads with less of an energetic burden.
I am not a biologist, but those parts just don't click for me; how/why would evolution have jump through all the costly hoops to differentiate the pelvis of males and females so significantly if the result was to give a locomotion system that was overall worse to the individuals who needed it the most for their survival, without any benefit in return ?
Men have deeper voices than women. What would be the disadvantage for baritone women? You could argue that a deeper voice makes you less easily heard by prey... but then what's the advantage for women to have a higher pitched voice? Why didn't we all continue this trend to speak at the registry of blue whales? I suspect it's one of those things that "just sort of happened" and then it became a positive feedback loop spurred on by sexual attraction as a result of this initial differentiation, and now we're just at a pretty good state spurred on by a combination of random chance, survival advantage, and a little reproductive enforcement.
Increased sexual dimorphism (and a genetic/hormonal configuration that lowers the cost and increases the odds of sexual dimorphism happening for any given feature) is actually a positive thing for some animals depending on their social and reproductive strategies. When sexual dimorphism is high, you tend to see more random differences that pop up between the sexes but that may or may not provide any evolutionary advantage beyond "well, the other sex is just attracted to it now so let's keep this party going." When dimorphism is low, differences generally have to provide a stronger survival advantage.
Evolution isn't always straightforward or "carefully thought out." The hoops it jumps through aren't always costly and don't always have a rhyme or reason. It's often chaotic and and takes weird turns and it's not like humans are at a "final state" anyway. We're evolving.
I'm not _necessarily_ disagreeing with you (although it's probably ultimately easier to look at the physics, not biology, to prove or disprove your point) but I'm just saying that I think the situation is vastly more complicated than "sexual differences are costly." I don't think they're necessarily costly, simply less likely. A subtle, but important difference.
Living in a neighborhood with a lot of teenagers, I will dare a guess; this loud, high pitched scream was probably a very efficient call for help.
But I see your point, and I agree that the answer could be just as simple as randomness of genetics. It just feels rather unsatisfactory for a change who must have taken far more than one single mutation to be that common. Feels like someone winning the lottery a dozen times in a row.
Individuals who have androgen insensitivity syndrome (XY chromosomes, but that don't respond to testosterone and are, for most intents and purposes, sterile females) will have large hips/pelvic bones.
So, yes, hip size takes a few modified base pairs (although probably all within one gene, or pretty close together on the same chromosome), but evolution only needs to "decide" (heavy emphasis on the quotes there) that this physiological change is hormonally triggered. Many skeletal changes are hormonally triggered, so this may have even been the easiest/most likely path.
Isn't the implied benefit that it might allow for an easier birth?
I assume men's hips are still better for tasks traditionally associated with the male gender role - e.g. being hunters and warriors.
Quoting a one-sided statistic like this is something the editor should have caught. The 5.5 miles figure doesn’t support anything if the figure for men is ten; it’s great support if that figure is four; but without either figure what does it mean?
I think that many women end up going into labour in a fearful frame of mind because of the constant reminders that it will be painful and this coupled with midwives intent on following timetables and doing things their way results in a stressful time for all.
As everyone else mentions, I am aware that my sample is not large and that there are many who have had a different experience.
As our brains became more advanced, our crania became larger and more dangerous to birth at full term. But as our intelligence increased, so did our ability to care for infants that were essentially born premature.
So now even our full term babies are born so early that they need another 3 months (sometimes referred to as the "fourth trimester") just to be mature enough to sleep properly, among other things. But as intelligent humans, we're able to care for them and devise ways to carry them with us and protect and nurture them despite their extreme helplessness.
FWIW, the offspring of carnivorous mammals, though not born quite as "premature" as humans, are often as underdeveloped at birth as a 3-month-old baby. I mean, have you ever seen a newborn kitten or puppy? Eyes closed, barely able to crawl to its mother's teats?
The need for a prey animal - especially one that depends on speed for self-preservation - to be able to escape from within minutes of its birth is very different from the survival requirements for a carnivore or even a prey animal that gives birth in a hidden den (like many rodents).
The fact that there’s such a spread for these otherwise extremely important life stages in humans shows a lack of maturity in their development compared to other mammals, not the inverse. Something is a little different about us.
It sounds harsh when discussing humans but the differences in development occur because our death rate is low compared to wild animals. Thus allowing weak genes to be passed e.g., not being able to crawl or walk for 3 years double or triple the normal would not be tolerated in the animal kingdom.
For example, if the child is delayed in walking because more metabolic resources are being channeled to larger brain development, that could be a survival benefit. I use that example, because that's essentially the theory of what happened in humans, in comparison to chimpanzees. (Obviously not 1 child randomly taking 2x or 3x to develop, but a slow evolutionary process.)
Chimps are relatively helpless when they are born too, relative to most species. They nurse for years, stay with parents for years, are totally reliant on them for survival, etc. But they are not so helpless as humans. It's estimated human gestation would have to be about 18 months for newborns to be at a comparable stage of cognitive development as newborn chimps.
So, from this perspective, we do take 2x the time in comparison to chimps, and yet it was tolerated. I guess my overall point is that evolution is more complicated than how quickly an offspring can crawl or walk or be independent.
On one side, I believe Doctors get paid more by performing a C-section. 
On the other, it may involve less risk, which reduces the likelihood of malpractice lawsuits? 
1 - https://scholar.princeton.edu/sites/default/files/dalexand/f...
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3096673/
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.)
A kangaroo leaves the pouch in around 8 months.
EEG suggests earlier born babies can have huge merits in intelligence evolution:
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
It looks like about 1% of pregnancies ended in death historically, and that matches what's happening in the places with the worst healthcare today.
With good healthcare, the risk nearly vanishes.
The article. Which quotes several expert anthropologists.