We can control (most of the time) whether or not we want to become pregnant. If assistance and/or drugs are desired for labor and delivery, they are available to us. A newborn giraffe doesn’t have the luxury of assistance. He drops six feet from mom’s womb to the ground. Ker-Plop!
Think about water mammals like dolphins and manatees. At least a human baby doesn’t have to nurse under water. In this video we see the bubbles escape from the baby’s nose as she exhales with her gulps, but she must swim to the surface to inhale her next breath. It’s really cool to watch!
In other ways, humans definitely have it worse than other mammals.
1. Morning sickness is a pregnancy symptom exclusive to humans. This is one way we’ve been screwed by evolution. Humans have a relatively dangerous diet. It seems that food aversions women experience are usually to the most risky foods in our diet. According to a Cornell University Study “nausea and vomiting in pregnancy is beneficial by expelling such foods as meat and strong-tasting vegetables that historically and still may contain harmful toxins and microorganisms.” This symptom typically happens in the first trimester when the fetus is most vulnerable. So, though unpleasant, this is the body’s way of protecting the fetus from potentially harmful food-borne bacteria, parasites, and toxins.
More details on that study here.
2. Labor and delivery for a first-time human mother averages nine hours. For our closest primate relative labor takes two hours. The evolutionary cause is two-fold. First, because we walk erect, our pelvis has added responsibility. To walk erect our pelvis needs to remain somewhat narrow. However, to give birth we need wider hips. A woman’s pelvis is wider than a man’s which gives her a little sway in her gait, but it’s not as wide as it could be if humans still walked on all fours.
Secondly, our babies are born large yet physically inept. Most mammals are born at 3% the size of the mother. Humans, however, are 6% of their mother’s size at birth. This makes for an arduous labor.
In utero, our energy goes to brain development. Studies even show the extra cushion of fat an infant has at birth is to support the baby’s brain development. The chubby physique is to make sure the body has good fat in reserves to support further brain development after birth. Other mammals are born skinny in comparison. If humans were to have a gestation period comparable to other mammals, a woman would carry a child for 23 months in utero. Instead, a fetus is carried for as long as possible (9 months) then delivery happens just before the fetus’ head grows too large to pass through the birth canal.
Even then, 1/1000 births are delivered surgically (*via cesarean) because the baby’s head it too big. This requires our infants to depend on mom much longer that other mammals do after birth. More details found here.
*Yes, there are many other reasons a baby is delivered via cesarean but this statistic focuses on head size.