Cambridge, Massachusetts. – It seems illogical to refer to the superior intelligence and larger brains of humans if they are asked what separates people from animals. However, the correct answer is the human pelvis. Scientists say it’s our unique pelvis that allows humans to walk upright on two legs, while also making it possible for mothers to give birth to babies with big heads (which includes these big brains).
Now, new research from Harvard University offers ground-breaking new insight into the development process of the human pelvis during pregnancy. While the pelvis is well understood on a purely anatomical level, little is known when it comes to how and when the pelvis forms during development. This new research changes all that.
The study authors discovered exactly when the pelvis forms during pregnancy, and identified the specific genes and genetic sequences that oversee the entire process. These findings may one day help shed more light on the genetic origins of bipedalism and may facilitate the development of new treatments or predictors of hip disorders such as hip dysplasia and Hip osteoarthritis.
This paper really focuses on what all humans share, the changes in the pelvis that have allowed us to to walk on two legs And it allowed us to have a large fetal head,” says study author and evolutionary biologist Terence de Cappellini, a recent professor in the Department of Human Evolutionary Biology, in statement.
How is the pelvis formed during pregnancy?
The study authors say that many very basic features of human walking and childbirth begin to take shape at about six to eight weeks During pregnancy. These developments include key pelvic features unique to humans – more specifically the curved, pelvic-like shape of the skeleton. Formation occurs when the bones are still cartilaginous, which means they can easily bend, rotate, expand and grow. Moreover, even when other cartilage in the body begins to turn into bone, the developing pelvic section remains like cartilage a little longer, giving the important structure more time to form.
“There seems to be a pause happening, and that pause allows the cartilage to continue growing, which is very interesting and surprising,” Cappellini adds. “I call it a protection zone.”
To make these discoveries, the study authors performed RNA sequencing. This showed which genes in the region actively lead to pelvic formation and stall ossification (the process by which soft cartilage turns into bone). Hundreds of genes that either “turn on” or “turn off” over a period of six to eight weeks have been identified to help form ilium in the pelvis. The ilium is the largest and highest hip bone With blade-like structures that bend and rotate in a pelvis to support bipedal walking.
Comparing the structure of human bones with that of apes
a Chimpanzee or gorilla They should shift their weight mass forward and use their knuckles to walk or balance themselves. Fortunately, the shorter and wider reorientation of our pelvic blades helps us humans avoid all that and walk on two legs instead. These same features also help to increase the size of the birth canal. In comparison, monkeys have much narrower birth canals and more elongated ilium bones.
The first steps of this project involved comparing the differences between hundreds of human and chimpanzee skeletal specimens, and the gorilla. The researchers explained that this process highlighted the amazing effect that natural selection had on the human pelvis, especially the iliac. Next, a selection of fetuses aged four to 12 weeks were studied under a microscope (with the consent of people who had legally terminated their pregnancies). The developing human pelvis samples were then compared to mouse models in order to identify the on and off switches that lead to pelvic formation.
“Walking on two legs affects the shape of our pelvis, which influences disease risk later on,” Cappellini concludes. We want to reveal that mechanism. Why pelvic picking affects the risk of later hip disease, such as osteoarthritis or dysplasia. Making these connections at the molecular level will be critical.”
The study Posted in science advances.