The human body is not the clever design triumph we might like to think it is
Parts of the human body are so badly designed you might think they were the result of a confused committee.
But we have evolution and nothing else to blame for our flat feet, bad backs, difficult birthing and useless wisdom teeth.
Intelligence was certainly not behind the design of some components of our body, researchers said at a session of the American Association for the Advancement of Science (AAAS) meeting in Boston.
Most of the difficult bits arose because our early ancestors began to walk upright on two legs rather than all fours. Difficult birthing emerged because of the rapid three-fold increase in the size of our brains and the skull shape required to hold them.
“Intelligent design is not apparent in the complicated way we have babies,” said Prof Karen Rosenberg of the University of Delaware. Our heads are large and the female birthing canal is narrow.
But humans were also social creatures that could lend help when needed, she said. The risk reduction this provided has allowed our species to deal with this evolutionary speed bump.
Flat feet
More problematic is the design of our feet, said Prof Jeremy DeSilva of Boston University. Its 26-bone design is not the first that would come to mind if you invented it from scratch. It provides springiness and assists bipedal walking, but its design has left us much more prone to ankle breaks, injury and flat feet, something our primate cousins, the apes, don’t have to worry about. “Many of the foot problems we have today go well back to the origins of upright walking,” he said.
Even worse is the design of the human spine and its letter-S curves, said Prof Bruce Latimer of Case Western Reserve University. He likened it to creating a stack of alternating cups and saucers, and then forcing it to have curves while also expecting it to bear weight.
This, in turn, leaves us vulnerable to a host of back problems with pinched nerves, damaged discs and even crushed vertebrae.
Our third molars, so-called wisdom teeth, were also worth considering, said Prof Alan Mann of Princeton University. “Evolution does not produce perfection,” he said. Brain and skull changes left us with a smaller jaw bone, one too short to accommodate the expected three molar combination seen in all previous primates.
We are now left with a problem: wisdom teeth may cause pain but not death, so evolution can’t readily weed the extra tooth out of the picture.
Prof Mann believes, however, that evolution may still have its way.
He pictures a person suffering from their teeth too willing to say, “Not tonight dear, my jaw is killing me,” an evolutionary scenario that could reduce the number of those carrying genes for three molars.
