Giving birth has been a complex, long and painful process since always. Not just that, it can also be deadly.
It had been estimated by the World Health Organization that about 830 women die every day because of the complications they face during pregnancy and childbirth. And you'll be surprised to know that this statistic is actually a 44% reduction on the 1990 level.
To this, a student of childhood nutrition at University College London in the UK, Jonathan Wells says "The figures are just horrifying. It's extremely rare for mammalian mothers to pay such a high price for offspring production."
But have you ever wondered what exactly makes childbirth so painful and fatal? And can anything be done to reduce those death rates?
Scientists began thinking about the problem of childbirth in humans in the mid 20th Century. They then came up with an idea that almost helped to explain what was going on.
They evaluated and said that the trouble began with the earliest members of the evolutionary lineage – the hominins. The oldest fossils of hominin found so far date back to about seven million years ago. The fossils belong to animals which share very few of our features, except one. As per the researchers, the hominins were able to walk upright on their two legs even at this early stage.
To make the hominin skeleton walk on two legs, it had to be pushed and pulled into a new configuration which would, in turn, affect the pelvis. The birth canal in the pelvis among the most primates is relatively straight. It soon began to look different. Where hips relatively became narrow and the birth canal became distorted – a cylinder which varied in shape and size along its length.
So, we can conclude that from the early prehistory, hominin babies might have had to twist and turn to pass through the birth canal. This whole thing would have made births far more difficult than it had been previously.
It was about two million years ago when our hominin ancestors began to change again. They ultimately lost their ape-like features which involved a small brain, short body, and long arms. In fact, they began to acquire more human-like traits like bigger brains, taller bodies, and shorter arms.
Evolution coming into conflict with itself was because the big-brained adults started out life as big-brained babies. On the one hand, the female hominins had to maintain a narrow pelvis along with a constricted birth canal so that they could walk efficiently on two legs. And at the same time, the fetuses they carried were evolving to have larger heads, which were far tighter to fit through those narrow pelvises.
Consequently, childbirth became a distressingly painful and a lethal business, which remains so to the present date.
In the year 1960, Sherwood Washburn, an anthropologist named this idea: the obstetrical dilemma, which is now often called as the "obstetric dilemma". Scientists were of the opinion that the idea perfectly explained the problem of human childbirth. And many think it still does.
But some scientists including Wells, are no longer satisfied with this standard explanation. In the last five years, several researchers and Wells have begun to push against the classic account of the obstetric dilemma. Where the Washburn's idea is very simplistic and that all sorts of other factors contribute to the problem of childbirth as well.
Holly Dunsworth, a grad student at the University of Rhode Island, Kingston was drawn towards the obstetric dilemma. She says, "I thought it was so exciting, I was going to find evidence that supported the obstetric dilemma, but very soon everything came crashing down."
Actually, the problem was with the predictions that Washburn made. Wells says, "When Washburn wrote his article, he was actually saying that the obstetric dilemma was solved by giving birth to babies at a relatively early stage in their development."
Tracing back to what we have talked about earlier, that two million years ago human brains began to grow larger, Washburn suggested that humans had found a solution of sorts i.e. shortening the length of the human pregnancy. Therefore, human infants were forced out into the world much earlier and they were relatively small with underdeveloped brains.
Though Washburn's explanation seems logical, anyone who has held a newborn would have appreciated how underdeveloped and vulnerable they are. The standard view is that the other primates hold onto their pregnancies for longer and give birth to babies that are more developmentally advanced. But, it is simply not true, says Dunsworth.
Holly Dunsworth says, "We have bigger babies and longer pregnancies than you would expect."
Human pregnancies are longer in an absolute sense, typically lasting for 38-40 weeks, whereas a chimpanzee gives birth after 32 weeks and orang-utans and gorillas' pregnancy last for 37 weeks.
Human pregnancies last 37 days longer than that for an ape of our size. The same applies for the size of the brain. Women give birth to babies with larger brains than we might expect of a primate with the average of woman's body mass. Which means that the key prediction of Washburn's obstetric dilemma come out to be incorrect.
And there are other problems too with Washburn's idea.
A central assumption of the obstetric dilemma is that the shape and size of the human pelvis, particularly of the female pelvis is highly constrained by our habit of walking upright on two legs. After all, if evolution could have solved the problem of childbirth simply by making the birth canal a little larger and woman's hips wider, it surely would have been done so by now.
But this assumption was questioned by Anna Warrener and her colleagues at Harvard University in Cambridge, Massachusetts, in 2015.
The metabolic data was collected by the researchers from the female and male volunteers who were walking and running in the lab. Volunteers who had wider hips were no more efficient at walking and running than their narrow-hipped peers.
Helen Kurki at the University of Victoria in British Columbia, Canada says, "The basic premise of the obstetric dilemma – that having a small or narrow pelvis is best for biomechanical efficiency – is likely not correct."
Her own research has identified more problems for the traditional obstetric dilemma hypothesis.
The female pelvis is tightly governed by two opposite forces; the need to be wide for giving birth and the need to be narrow for walking. Also, the shape of the birth canal varies with women. So, it has to be stabilized by natural selection.
In 2015, after analyzing hundreds of human skeletons, Kurki reported that the birth canal is extraordinarily variable in shape and size – it varies even more than the shape and size of the human arms.
Kurki says, "I think my findings do support shifting attitudes to the obstetric dilemma."
Washburn's narration now does not seem as satisfying as it once did. There might be something else going on.
Holly Dunsworth is of the opinion that she has successfully identified one important missing clue in the puzzle: energy.
Dunsworth shared (being a mother), "We max out toward the end of pregnancy. Those last weeks and months of pregnancy are tiring. They are pushing right against the possible sustainable metabolic rates in humans. It has to end at some point."
Sometimes pregnant women joke that their fetus which is in a developing state feels as if it is an energy-sapping parasite. And in a sense, its energy demands grow with every passing day.
Whereas, in particular, human brains have an appetite for energy which is almost insatiable. Metabolically speaking, the tiny brain, growing by second inside the womb can push a pregnant woman close to the edge.
Dunsworth thinks that it's a human tendency to obsess too much about the tight fit between mother's canal and a baby's head. People say that it is a coincidence that the two are naturally so close in their sizes but she says that the pelvis has simply evolved to be the size it needs to be.
By and large, Kurki shares this view. "The obstetric canal is big enough, the majority of the time, for the foetus to pass through."
Although this is true, have a look at the stats of maternal mortality: 830 deaths per day. Even in the cases in which women do not lose their lives, some studies say that the process of childbirth leads to life-changing yet non-lethal injuries in about 40% of cases. And the price women pay for childbirth is extraordinarily high.
To this Wells said, "It's impossible to imagine the problem has been this bad over the long term."
Perhaps in 2012, Wells and his colleagues searched into the prehistory of childbirth coming up with a surprising conclusion. They said childbirth might have been a lot easier.
Wells and his colleagues feel that childbirth might have been relatively a minor problem in our species. Very few skeletons of newborn baby among the human remains gathered from the early hunter-gatherer groups, hinting towards a low rate of death rates among newborns.
Apart from the death rate, Wells also came out with an evidence that there is a link between a woman's height and the shape and size of her pelvis. Say, a shorter woman might have narrow hips.
Now, there is a new explanation regarding the difficulties of human childbirth. Pregnant women started nourishing their fetus for as long as they can before it grows too large to feed internally. Also, the pelvis of females had adapted to be just the right size allowing maximally-nourished fetus to travel through it safely. But however, the dietary changes in the last few thousand years have disturbed this balance, making childbirth risky.
And according to Dunsworth, this was probably not the end of the story.
Washburn's ideas made good sense for decades until Wells, Kurki, Dunsworth and several others began to pull them apart. Dunsworth asked, "What if the EGG perspective is too good to be true? We have to keep searching and keep collecting evidence."
And this is what other researchers are doing. In the year 2015, Philipp Mitteroecker of the University of Vienna, Austria and Barbara Fischer of the Konrad Lorenz Institute for Evolution and Cognition Research in Klosterneuburg, Austria also took a look at the female pelvis.
They came out with a thought that Dunsworth's EGG hypothesis could be seen as complementary to Washburn's ideas, rather than disapproving them.
Mitteroecker and Fischer then investigated whether there is any correlation between a female's head size and her pelvis. However, head size is heritable to some extent, consequently, women with larger heads would benefit during childbirth because they naturally had a wider pelvis.
Perhaps, their analysis of 99 skeletons suggested that such a link indeed exists. Concluding that a woman's head size and her pelvic dimensions might somehow get linked at the genetic level.
To which Fischer says, "This does not mean that the problem of childbirth has been resolved." And the problem would be even worse if there existed no link between a female's head size and the pelvis width. Yet there is another complication i.e. women's bodies change as they get older.
A study that was conducted in May 2016 by Christoph Zollikofer and Marcia Ponce de León at the University of Zurich, Switzerland took 275 people into research including both male and female of all ages. The study concluded that the pelvis does change dimensions during the course of a woman's lifetime.
The researchers' data suggested that a woman's pelvis takes on a shape which is more conducive to childbirth in her late teens, at the time of her peak fertility. It then stays in that shape until she turns 40, then it gradually changes shape to become less suitable for childbirth, and getting ready for the menopause.
Scientists call this series of changes as the "developmental obstetric dilemma" (DOD).
But if all these evolutionary pressures are acting on childbirth, is the process still changing and evolving even now?
In December 2016, Mitteroecker and Fischer addressed this question, subsequently making headlines with their theoretical paper.
Earlier studies suggested that larger babies stand a better chance of survival and also the size at birth is at least somewhat heritable. These factors together have the probability of leading the average human fetus to push up against the size limit imposed by the female pelvis, even though it can be deadly to push too far.
But nowadays, a large number of babies are delivered by a Caesarean section, where the baby doesn't even enter the birth canal.
Wells says, "We all either did or didn't arrive in the world through a pelvis. If we did, that pelvis mattered. And if we didn't, that in itself is interesting."
Ever since the phenomenon of birth evolved, babies have been constrained by the size of the birth canal to some degree.
But maybe, this is no longer true... for some babies at least.