This method, more commonly used in engineering projects, uses mathematics to test how structures would likely react to real-world forces, such as vibration, heat, fluid flow, and pressure.
After testing a wide range of pelvic floor sizes and thicknesses, the results suggested that the pelvic floor hypothesis is correct. Key Takeaways. Stephen Johnson. Human childbirth is a relatively painful and complicated process in the animal kingdom. Evolutionary trade-offs A study recently published in Proceedings of the National Academy of Sciences proposes that human childbirth is difficult because of evolutionary trade-offs that ultimately help protect organs in the body.
In this article. The Present. Daylight saving time was first implemented during the first world war to take advantage of longer daylight hours and save energy.
The underlying concept here is that wider-hipped women—capable of giving birth to larger offspring—should suffer a disadvantage in locomotion.
Men and women are extremely similar in the cost and efficiency of locomotion, regardless of hip width. Enlarging the birth canal to pass a baby with a brain 40 percent of adult size, as is typical of newborn chimps, would require an increase in diameter of only three centimeters—just over an inch—in the smallest dimension of the birth canal.
The conflict between big-brained babies and upright walking may be more conceptual than real. Although the findings showing that human babies are not earlier than other primates are interesting, they still fail to identify what limits baby brain size. Dunsworth and her coauthors propose that the metabolic constraints faced by a mother limit the length of pregnancy and fetal growth. They have dubbed their hypothesis the energetics-of-gestation-and-growth hypothesis.
Holly Dunsworth and colleagues contend that because adult brain size in humans is much larger than in other primates for reasons having nothing to do with birth, using adult brain size as a basis for comparing primate gestation length or newborn brain size will underestimate that of humans. Graphs adapted by Barbara Aulicino from H.
Dunsworth, et al. As the baby grows in both brain and body in the womb, its demand for energy accelerates exponentially. Even following birth, the big-brained, big-bodied newborn needs a loving mother who will continue to feed and care for it while its brain continues to grow at a fetal rate.
In the womb, the fetus is basically part of the mother. Once born, the baby is effectively at a higher trophic level than its mother, like a parasite feeding on her, which increases the metabolic demands on her.
The obstetrical hypothesis is not defunct; it is simply under question. But merely convincing those who were raised intellectually within this paradigm to consider an alternative hypothesis can be challenging. When she gives a talk about the energetics hypothesis, Dunsworth summarizes a conversation that illustrates this challenge:. Pelvic size may be limited by something not yet taken into account in locomotor studies, such as speed, balance, or risk of injury.
Or, perhaps simple economy keeps pelvic size close to neonatal brain size. The third alternative is that human childbirth was not always difficult and has only become so as improvements in diet have increased newborn body size. The obstetrical hypothesis and the energetics hypothesis are not mutually exclusive. Perhaps the real problem is making one. Skip to main content. Login Register. Page DOI: Illustration by Tom Dunne. Witness over seven billion humans on the planet.
Bibliography Albers, L. The duration of labor in healthy women. Journal of Perinatology — Dunsworth, H. Anthropologist finds explanation for hominin brain evolution in famous fossil May 07, May 15, Sep 17, Recommended for you.
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Your message to the editors. Your email only if you want to be contacted back. Send Feedback. Thank you for taking time to provide your feedback to the editors. E-mail the story Computer simulations show human ancestors would have had an easier time giving birth than modern women.
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