Evolution: The parts of the body that we are losing

Can you make your ears move without touching them? Apparently it is a rarity to have that ability. It is also pretty useless. It will no longer serve you for anything except to have a laugh with friends. Millions of years ago our ancestors had that ability, and then some, as it was vital to detect prey when they went hunting and also to alert them of predators. As with that muscle that makes your ears move, there are other parts of the body that we humans still retain – not everyone, mind you – and they have lost their usefulness over time.

There is one muscle that runs from the wrist to the elbow - another vestige of the past. "If we extend our arm with the palm of the hand facing upwards and join the thumb with the fingers, a thin, straight protuberance appears that extends along the forearm," explains physiotherapist Raúl Moreno. Some 14% of the population has already lost it with no negative consequences. "Surgeons have been using the palmaris longus tendon for many years to replace other tendons when they snap: it is easy to extract and has no consequences," he adds. Some theories suggest that it was used by our ancestors to exert the strength necessary to climb trees.

Between five and eight weeks after conception the foetus begins to develop a tail that then disappears before birth to form the coccyx. "The tail was used to move and maintain balance. But when we learned to walk upright, it was lost because it was no longer necessary," according to a Boston College (USA) study by the evolutionary anthropologist Dr Dorsa Amir (now at Duke University, California).

Spain's General Council of Dentistry estimates that 25% of the population is missing one of the four wisdom teeth (our third molar), and this percentage is increasing because these teeth simply do not form. Moreover, 10% of us are missing them completely. It is a natural evolutionary process to lose them. The function of this third molar was to chew tough meats and the raw cereals that our ancestors ate. "Our diet is becoming softer, which means that a jaw as large and strong as before and so many teeth are no longer necessary."

"Very few people still have control over the muscles that move their ears," comments the physiotherapist. Some mammals use them to detect prey or predators and it is believed that humans used this ability for the same purpose of survival. However, since humans stopped hunting to survive, this ability has been lost.

The passage of time has also affected our sense of smell. Throughout our evolution, hominids have gradually lost the number of olfactory receptors in favour of other senses, such as eyesight.

The contraction of these muscles (arrector pili) causes the goosebump effect. They are small muscles connected to hair follicles in mammals and they served a function when our ancestors had a lot of hair all over their bodies as this effect increases the volume of the body as a defensive strategy. Having those body hairs stand on end also made humans appear larger when attacked by an animal, which protected them to a certain extent. The formation of goosebumps on the human body is a vestigial reflex that no longer serves any physiological function. Its original, primitive role is still seen in animals such as porcupines that stick out their quills when threatened, or cats with bristling fur, especially in their tails, when faced with danger.

It is just a fold located in the inner corner of the eye and resembles the membranes found in some animals such as birds, reptiles and even some mammals (cats, for example). It serves to protect vision and keep the eyes moist and free of debris but, in the case of humans, only a small part of this membrane remains and, furthermore, we no longer have control over it.

The appendix is a finger-shaped pouch that projects from the colon, on the lower right side of the abdomen. "It seems to be a vestige of when we were herbivores and had to digest large amounts of cellulose from plants," says the Spanish Society of Family and Community Medicine (SEMFYC). In fact, vertebrates that eat plants still rely on their appendix to help process this food. "But when we began to change to a more diverse diet and focused on meat, it was no longer necessary." So how about now? It could have some residual immunological role. "Acting as a refuge or reservoir for the microbiota (intestinal bacterial flora)," say SEMFYC sources.

Nipples serve a specific purpose: breastfeeding offspring. So, why do men have nipples if they won't be able to use them? "During the first few weeks, male and female embryos follow the same growth pattern, including the development of nipples," notes the report by American anthropologist Dorsa Amir. However, at 6 or 7 weeks of gestation, a gene on the Y chromosome induces changes that lead to the development of the testes and the production of testosterone – from 9 weeks onwards – altering the genetic activity of the cells in the genitals. But by then, the nipples are already there, although subsequent human development renders this vestigial structure useless.