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Nana: Ooh my back!

Nina: Did you know it could be a fault of evolution?

Nana: Whatever are you mumbling about? I have always tried to maintain a good posture, but back pain has been an age old problem from me.

Nina: It’s not your fault, Nana. Scientists have found that our evolution to bipedalism, with all the advantages it confers, also leads to many problems.

Nana: You mean, my back pain may not be my fault? How so?

Nina: Bipedalism evolved from quadrapedalism. In quadrapeds the spine is horizontal and operates like a suspension bridge.

Nana: That sounds quite stable.

Nina: It is, Nana. But in humans, the spine is very precariously built. A scientist, Latimer ,compared the spine to a tower of 24 cups and saucers, with each cup representing a vertebra in the spine and each saucer one of the discs between each vertebra.

Nana: Yikes!

Nina: That’s not even the worst of it. The spine also curves to help us balance our torso upright. Latimer added that imagine a book like a dictionary added to the top of those twenty four tea cups to represent our head.

Nana: Good grief! Sounds like an engineering nightmare.

Nina: Evolution hasn’t had enough time to perfect bipedalism yet, and recent studies have found that the vertebrae of people suffering from spondylolysis tend to deviate further from those of the great ape than the vertebrae of healthy humans.

Nana: Now you’re confusing me. That can’t be the case, if evolution of bipedalism is the root cause of spondylolysis. How can more evolved spines lead to more problems?

Nina: Actually, the scientists call this the overshoot hypothesis, where in evolving away from quadrupedalism to bipedalism the development of the vertebrae have overshot the optimum.

Nana: Oh, so you’re saying that the evolutionary process is not yet complete in regards to bipedalism, and right now some of us have over corrected spines, and with further evolution, the optimum will eventually be achieved.

Nina: Perhaps not, Nana, for now society, technology and medicine develop at such rapid rates, that natural selection simply can’t keep up.

Nana: I knew there would be trouble when you started reading The Selfish Gene. Do you have to discuss everything you learn? Can't you keep it to yourself?

Nina: No. The book was such an awesome read. It got me really interested in evolution, so I read a lot of articles on the subject too. Our feet too evolved from the feet of arboreal species making everything a lot more complicated, weird and quite suboptimal.

Nana: How so?

Nina: The human foot is made of 26 bones. Our feet together account for a quarter of the bones in our body.

Nana: You’re kidding.

Nina: No, Nana. Human feet evolved from feet of arboreal apes that used their feet much like hands to clasp tree branches to get around. They had an opposable big toe, unlike us.

Nana: Holy Toe-ledo!

Nina: Aren’t you punny today! But it’s true. Feet that could bend and flex much like hands then adapted for bipedalism with stiffening muscles, ligaments and tendons. It isn’t optimal but it’s the best evolution could do in this time, given where it started. Actually, it has been described as, using duct tape and paper clips to patch together and stiffen up the foot.

Nana: You’re exaggerating. I think we do a pretty good job of surviving. You make us sound like an evolutionary disaster.

Nina: Not a disaster, Nana. Just work in progress and we compensate for our weaknesses with our intelligence and ability to co-operate. Also, there are some physical superpowers our bipedalism has given us?

Nana: Really? What? You were starting to make us sound hopeless!

Nina: Humans are actually great at endurance running. Over long distances, we can outrun horses. In fact, that is how ancient humans would hunt, by tiring out their prey and leading them into traps.

Nana: But is that good for you? I mean, it sounds really stressful.

Nina: It’s super healthy, Nana. Great for reducing body fat, losing weight and lowering heart rate.

Nana: Excellent. So go on. Run fifty laps around the house.

Nina: I guess you used that endurance strategy and walked me right into a trap. Diabolical, Nana. Well played. I should have known there was something fishy going on, when you complained so little during this discussion. I suppose it is good for me, but I hate running. WAAAaaah... boo hoo hoo.

This post is a part of the #NinaAndNana series I co-host with Lavanya Srinivasan. Her posts can be found here.