Five Body Parts Humans No Longer Need [Health]

Five Body Parts Humans No Longer Need

Five Body Parts Humans No Longer Need

Vestigial organs are parts of the body that once had a function but are now more-or-less useless. The most famous example may be the appendix, though it is now an open question whether the appendix is really vestigial. Here are five organs and functions most likely to be truly vestigial: Vomeronasal Organ Rodents and other mammals detect pheromones with a specialized sensory system called the vomeronasal organ (VNO). It consists of a pair of structures that nestle in the nasal lining or the roof of the mouth. Most adult humans have something resembling a VNO in their nose, but there are no nerve fibers connecting it to the brain. Humans probably detect pheromones with their main olfactory system instead. Goose Bumps Goose bumps aren't a body part, but the reflex is widely considered to be vestigial in humans. They occur when tiny muscle at the base of a hair follicle contracts, pulling the hair upright. For creatures with feathers, fur or spines, this creates a layer of insulating warm air in a cold snap. But human hair is incapable of this functions. Darwin's Point Around the sixth week of gestation, six swellings of tissue called the hillocks of Hiss arise around the area that will form the ear canal. Darwin's point is a minor malformation of the junction of the fourth and fifth hillocks of Hiss. It is found in a substantial minority of people in the form of a bump on the rim of the outer ear. It is thought to be the vestige of a joint that used to allow the top part of the ear to swivel or flop down over the opening to the ear. Tail Bone The human coccyx is a vestige of the mammalian tail which has taken on a modified function as an anchor point for the muscles that hold the anus in place. There are, however, more than 100 medical reports of babies born with tails, which occurs if the signal that normally stops the process of vertebrate elongation during embryonic development fails to activate on time. Wisdom Teeth Most primates have wisdom teeth (the third molars), but a few species have none. It is likely that when the body size of mammals reduces rapidly, their jaws become too small to house all their teeth, and overcrowding eventually results in selection for fewer or smaller teeth. As many as 35 percent of people have no wisdom teeth at all, suggesting that we may be on an evolutionary trajectory to losing them altogether. Sources: ABC News May 22, 2008