A couple of years ago, I was talking to a friend who had just built an IKEA bookshelf.

“It looks great,” she told me. “And I barely had any extra parts!”

These days, wise in my old age, when I put together furniture, I tend to read the instructions through once or twice first, then follow them to the letter. And, invariably, all of the included parts end up in the finished product.

Simply put, manufacturers are controlling costs to the penny, and they don’t just throw in a few extra bolts for good measure.

Evolution works the same way. Developing biological structures in a growing body is extremely physically costly. Nature is parsimonious. So it would be surprising to discover that we have major physiological structures ‘by mistake’.

Indeed, over the last few decades, we’ve increasingly discovered that organs we once believed were vestigial – evolutionary ‘leftovers’ – actually serve important functions that we simply hadn’t yet discovered.

Consider the appendix, which paleontologist Alfred Romer once joked served primarily “to support the surgical profession.” In the last fifteen years, we’ve discovered that it’s crucial in early childhood, aiding in the maturation of B lymphocytes and the production of antibodies. And a growing group of scientists has suggested it also serves as backup reservoir of good gut microbes, so that we can healthily ‘reboot’ after illness. Individuals without an appendix, for example, are four times more likely to suffer from C. diff. colitis, a bowel irritation caused by the overgrowth of bad bacteria.

As a result, I’m particularly dismayed by the number of surgical interventions that ‘fix’ problems by simply disposing of structures that are the current source of problems.

Consider gastric bypass, the current state of the art in bariatric medicine. To help people lose weight, a bypass reduces the size of the stomach, to decrease appetite, and then routes the vast majority of the food around the large intestine entirely, to keep people from absorbing the majority of the food they eat. Problematically, different parts of your intestines absorb different kinds of food, so that ‘reduced absorption’ caused by arbitrarily skipping parts is actually a short path to unbalanced malnutrition. And the skipped gut serves all kinds of immune and neurological functions beyond simple digestion, which we lose when we indiscriminately cut it out of the picture. Further, dumping food into later parts of the intestine in a less-digested state causes additional problems, because those later parts weren’t designed to function properly with that kind of undigested input.

You can argue here as to whether the doubtless deleterious effects of wrecking your digestive system is outweighed by the more pressing disaster of morbid obesity. But you can also lose weight by cutting off your legs, yet fewer medical centers have popped up around that idea, mainly because the missing legs are a more immediate problem than those caused over time by a bypass.

Similarly, I’ve talked to a number of orthopedists who proudly ‘treat’ plantar fasciitis surgically by cutting the plantar fascia. Your plantar fascia is tight and painful? We’ll just snip that thing, and everything will be great! Except, obviously, it won’t. Your plantar fascia plays an important role in the structure of your foot, and in the way you stand, walk and run. With yours missing, you’ve created a slew of new problems. Whatever underlying disfunction caused the plantar fasciitis hasn’t disappeared; it will just slowly start wrecking a different portion of your body, further up the biomechanical chain.

You can see this clearly in surgeries like total knee replacement. Your knee is meant to bend in a straight line, but if you spend enough years putting weird torque into the system due to wonky movement patterns, you’ll eventually wear through the cartilage that’s meant to serve as side-rails, rather than as a primary support surface. After that, you’ll start to grind away the bone, which really hurts. So an orthopedist can solve the problem by removing your knee completely, and replacing it with a metal version that’s simply too strong for you to torque it in a damaging way. Problem solved! Except, of course, it hasn’t been solved here, too. Your wonky movement patterns persist, but because you can no longer get play in the system at the knee, your body start compensating at the hip or low-back instead. Indeed, after total knee replacement, the odds of needing surgical intervention at the hip or low-back skyrockets. But don’t worry, we can also fix those. We can replace your hip with a metal version, too. Or, if the bendy parts of your spine aren’t moving the way they should, we can just fuse them together so they can’t move any more. We’re great at this!

All of which is to say: your body is a hugely complicated system, which operates holistically in ways that we’re just beginning to understand. Giving real thought and research to how different inputs change the output of that system is probably a smart route to finding solutions that are helpful in the long-term. But removing ‘extra parts’, and then not expecting that to cause all kinds of new and unexpected problems seems a rather myopic way to go.