Almost 100 years ago, the Russian biologist, Ivan Schmalhausen, developed the Stabilizing Selection theory. He described how a species that evolves to be excellent at one thing tends to become more unsafe to another. That’s why there are no perfect species.1Source: Smithsonian Institute
For example, a tall tree captures more sunlight but it becomes more susceptible to wind damage. Siberian huskies need a lot of muscle to pull sleds, but they have to remain light enough to stand atop the ice.
Among humans, babies of low weight lose heat more quickly and get ill from infectious diseases more easily. Meanwhile, larger and heavier babies are more difficult to deliver through the pelvis.2Source: Memorial University That’s likely why most people have “average” height. It’s easier for humans to survive when they’re born with just the right birth weight.
There are always inefficiencies in nature. Becoming perfect tends to backfire, so species rarely evolve to become perfect at anything. These imperfections are what allow us all to survive and thrive.