Why do our feet have so many sweat glands?
There are more sweat glands per inch in our feet than anywhere else in the body. Their function is to keep the skin moist and supple and regulate temperature when the weather is hot, if you have an unnaturally high temperature or while exercising. They secrete all the time, not just in response to heat or exercise, like elsewhere in the body. Excessive sweating, also known as hyperhidrosis, has a lot to do with how the sweat glands in the feet work. With 250,000 sweat glands, feet do tend to sweat more than other parts of the body, but with a daily hygiene routine few people should suffer from the embarrassment that it may cause.
To answer the ‘why’ part of the question, let me first say that the eccrine sweat glands on palms and soles respond to emotional stress, rather than increased body temperature 1. With that being said, the answer to the ‘why’ part becomes likely to get changed. As one might know, its pretty difficult to answer the ‘why did this happen during evolution?’ question; there can be only theories with (usually) no conclusive proof. So, in this case too, the ‘why’ part remains without conclusive answer, and just theories prevail. According to the most prevailing theory, the emotional sweating causes sweaty palms that can help control the humidity of the outer layer of the skin. This could improve the friction on the skin thereby helping when you begin to sense you will be hunting an animal, fighting enemies, or about to climb a cliff (just to add, ever thought why your fingers get wrinkly after a long bath?). The generalized sweating that results from your hypothalamus then helps cool the body when these intense physical activities are happening. It also produces an odor that sends out pheromone signals to those same enemies/animals. The pheromones also could help signal potential mates that you are natural selection’s answer to their mating needs2. Again, this is just a theory and likely to have flaws, while the definitie answer is still not known. You can also have a look at the answers to this question for some more details.
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