'The Scars of Human Evolution' briefing explores physical fallout from 2-footed walking

February 15, 2013

From sore feet to backaches, blame it on human evolution.

"Because we are the only mammals to walk on two feet," says Bruce Latimer, an anthropologist from the Case Western Reserve University School of Dental Medicine.

Latimer will present "A Backache of Longstanding: An Evolutionary Perspective on the Human Vertebral Column" at the 2013 American Association for the Advancement of Science's annual meeting in Boston, Feb. 14-18. His talk will be featured in the session, "The Scars of Human Evolution."

Latimer and other panelists will explain how adapting to upright walking has resulted in physical challenges that affect most humans. A news briefing at 10 a.m. is scheduled on Friday, Feb. 15, in Room 103, Hynes Convention Center and precedes afternoon talks in Room 302, also in the center.

"If an engineer were given the task to design the human body, he or she would never have done it the way humans have evolved," Latimer said. "Unfortunately, we can't go back to walking on four feet. We've undergone too much evolutionary change for that--and it is not the answer to our problems."

But applying Darwinian evolutionary theory to the human condition offers a window to why humans suffer from physical ailments that no other animals do, said Latimer, who is on the faculty in the Department of Orthodontics at Case Western Reserve.

Evolving from four-footed walking has created issues from flat feet and bunions to slipped discs, hernias and fallen pelvic floors. And as bizarre as it sounds, rising from four to two feet resulted in reshaping the face and head, which is why humans suffers with such dental problems as wisdom teeth with no room to grow.

Latimer's talk will focus on physical problems of the spine, which developed into an S-shaped structure as humans shifted from quadrapedal walking to bipedal walking. But changes to the spine also resulted in protecting the body's most important area, the birth canal, which allowed the species to procreate.

As the spine developed in curves, it became stressed at certain points, resulting in such conditions as lordosis (swayed backs), kyphosis (rounded upper back or hunch back) and scoliosis (sideway curve).

The spine also takes a beating from how people walk--one foot forward at a time with the opposite side arm swinging in step.

"This creates a twisting motion that, after millions of twists over time, the discs between the vertebrae begin to wear out and break down resulting in herniated discs. In addition, age related bone loss (osteoporosis, the brittle bone disease, ) also a human condition, further complicates problems, Latimer explained.

Few early species of ancient human hominids lived beyond 50 years. Most died between 30 and 40, Latimer said. The human body really takes a physical beating, and most people will struggle with some kind of pain as the body ages.

"The original design specs for the human body were designed to last about 40 years," he said.

Other talks in "The Scars of Human Evolution" session include Rachel Caspari from Central Michigan University on the consequences of living longer; Jeremy DeSilva, Boston University, on problems with the human feet; Alan Mann, Princeton University, on the evolution of head and jaw; and William Leonard, Northwestern University, on nutritional health and evolution. Caspari and Karen Rosenberg, University of Delaware, organized the panel. Responding to the talks will be Milford Wolpoff, University of Michigan, and Matt Cartmill, Boston University.
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Case Western Reserve University

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