What has two legs and walks upright?
Scientists at the University of Austin, Texas confirmed the pivotal role that the position of the foramen magnum had in the transition between four-legged and two-legged walking. What is the foramen magnum?
This Latin term meaning “great hole” is the gap in the base of our skulls where our spinal cords run down our vertebrae to the rest of our bodies. If you think of our skulls & vertebral columns as a lollipop on a stick, the foramen magnum is the hole in the candy where the stick goes.
How does this hole differ between four-legged and two-legged animals? From Science Daily,
The foramen magnum in humans is centrally positioned under the braincase because the head sits atop the upright spine in bipedal postures. In contrast, the foramen magnum is located further toward the back of the skull in chimpanzees and most other mammals, as the spine is positioned more behind the head in four-legged postures.
Other upright species, such as the kangaroo, also have centrally located foramina magna (plural)—perhaps due to convergent evolution. As the picture above shows, we humans are quite upright as compared to other mammals. Thanks foramen magnum, for letting us stand up straight!