Brain expansion: the obstetric dilemma (Evolution)

by David Turell , Friday, May 07, 2021, 20:56 (1083 days ago) @ David Turell

Even an early form like Lucy may have had problems before the giant brain appeared:

https://www.dailymail.co.uk/sciencetech/article-4451168/Ancient-human-ancestor-Lucy-nee...

"She is one of mankind's oldest and best preserved ancestors and is more than three million years old.

"And now new research suggests that 'Lucy', along with others in her species, may have needed a midwife to give birth, due to the shape of her pelvis.

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"Researchers from Dartmouth College in New Hampshire were studying how Lucy and her relatives would have given birth, and found that it would have been in a manner in between that of chimpanzees and humans.

"While there are no known fossils of any newborn australopiths, the researchers modelled the shape and size of an infant's head by assuming it had the same dimensions as a large baby chimpanzee.

"They also estimated the width of an australopith baby's shoulder by looking at the relationship between the shoulder widths of adult and newborn primates such as humans, chimps, gorillas, orangutans and gibbons, and by examining the width of Lucy's shoulders.

"The models indicate that, as happens in humans, a baby australopith would have entered the birth canal sideways.

"But the researchers also suggested that an infant australopith would have had to tilt only slightly to make way for its shoulders as its head slid down the birth canal, instead of its head rotating 90 degrees as happens with human babies during childbirth.

"These findings suggest that there was a tight fit between the infant and its birth canal,.

"This mean Lucy might have had some difficulties during labour - just like modern humans.

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"Modern humans give birth in a very different way to their primate relatives.

This is most likely due to the large size of the human head and the way a woman's pelvis is positioned for upright walking.

"Human babies fit snugly inside the birth canal, meaning that women often require assistance during delivery.

"But other female apes do not have this problem, meaning that instead, 'mothers can just reach down and assist with their own births,' Dr DeSilva said."

Comment: The dilemma refers to this problem. In evolving our big brain with a pelvis that supports upright walking, the mother's pelvis bony outlet had to enlarge at the same time a bigger brained fetus appeared. And this also involves the Dad's DNA input. Lucy's problems point this out. A baby 'Lucy' brain was very small but the newly shaped walking pelvis presented trouble. Our evolution had to be guided by a designing mind, God, as our bigger brain kept evolving bigger and bigger. Three different DNA's contribute to a three-way evolutionary input.