Proof of Evolution That You Can Find on Your Body

Biologia-Vida | Image:  Rosalyn Schanzer.

 Let's start by the crucial (and common) question: if humans evolved from monkeys, how come there are still monkeys? Why haven't they all evolved to human?

A basic thing you need to understand about biology: HUMANS DID NOT EVOLVED FROM MONKEY, WE HAVE A COMMON ANCESTOR.

Evolution does not happens in a straight line, a species does not become another; individuals breed and genetic mutations happen over time; physical barriers (such as mountains or rivers) separate individuals who, being in different niches have different needs and end up suffering parallel pressure of natural selection. That is, the monkey is not your grandfather who turned into you, the monkey is your cousin who lives at the same moment of you and have a grandfather (ancestor) in common with you. You two are connected by a common base, but as the needs were different and habits were different, the monkey and the man followed different evolutionary paths.
 

Big size image here(it's worth). Image: Leonard Eisenberg

That cleared, here are the features that make your body a natural history museum: vestigial organs that exist in your body and have no purpose for you today but that were very helpful to an ancestor. They continue on your body because they make no difference on your day by day actions, neither good or bad, so there is no action of natural selection and these characteristics neither favor or hinder individuals.

1) Place your wrist faced up on the table and touch the toe in the little finger. The tendon that you see standing out in the forearm connects to the palmaris longus muscle and around 15% of people do not have it in one or both arms, which does not make the grapple of those people weaker; in fact, in some cosmetic surgeries that is one of the first tendons removed to rebuild another part of the body (ie, it does not missed). You find the palmar muscle in various mammals, although it is more developed and is constantly use in primates that use the hind limbs (arms) for going through the trees.

 The length of this muscle varies according to the species of primate, going the ones that move through the branches and need the arms for support (such as lemurs) to the vestigial (without function and reduced) in humans (since we do not depend on our arms to get around, "thanks Darwin").

 2) Other vestigial muscles that are used by other existing species (dogs, cats, bear, among others) who have inherited this feature from an ancestor in common with us, but  have no use for humans (although we have inherited because natural selection have not  eliminated since it doesn't make a difference) are three muscles around our ear, called the auricular anterior, superior and posterior muscles.

Although humans can not move this muscle very much, other animals use them to move the ears toward the sound source. This can presumably be very useful for nocturnal mammals, being alert for predators approaching. Some studies connecting electrodes in the ear of a man show these muscle activities trying to (and failing, poor things) move in the direction of sounds made out of the view of the individual. In other words, we do not need these muscles, but they still try to fulfill their function (now useless to us).

 3) Another action that happens in our body but has no useful application to us you can notice when you get goosebumps: when you get cold, tiny muscles attached to each fur  contract, making it stray up and the skin around it form a bump. Needless to humans, but for our hairy relatives mammals such as foxes and bears, for example, it increases the area of ​​thermal insulation, keeping them warm. In fact, birds do it too, you may have noticed a bird getting the ruffled feathers in the cold: evolution it's beautiful, man!
Adrenaline is one of the hormones responsible for the responses of the body to cold and also gets released in times of stress, so it also helps the image of the animal during fight: by bristling it's fur or feathers, it looks bigger and scarier, and sometimes he wins the fight only by that look without wasting energy with physical fight. Have you ever seen a cat or dog ruffling the hair when it sees another animal in its territory? Evolution is beautiful, man²!!
Incidentally, this  (adrenaline release) can also be the reason why we have chills neck when we listen to a fantastic music or have a strong emotion.

 4) We have to mention: our tail. At the end of our spine has a 3 to 5 fused vertebrae, the famous coccyx. It serves today (to the human being) as a support for some pelvic muscles, but it is what remains of our ancestors tail (and is still developed in several other species RELATIVE TO US). In fact, we all had tail at a time of life: at the beginning of development the embryo has a tail like many other mammalian embryos, but the cells that constitute it are programmed to die after a few weeks, although in rare cases some babies are born with a vestigial tail (which can be removed surgically for aesthetics).

By the way, a vestigial behavior that we inherited from an ancestor that moved through the trees and had to, from the first moment of life, be able to hold to the mother's body or on the branches to keep safe on high (such as current primates relatives) is the reflects that newborns have on holding on to anything you put on their hand (we usually offer our finger because we find it cute without knowing why he holds), and he has this reflex in both hands as toes. A study conducted in the 30s (probably would be unethical to promote it today for obvious reasons) were designed to compare the development between man and woman in identical twins, and one of the shooting shows the two babies of only one month old holding a bar for an amazing time, and managed to hold their whole body just by their hands.

So, do you still feel like the most evolved being?

Sources: MedWorks / Vox video / Anatomia Online / A study of Johnny and Jimmy/ Science Alert 

Postado por Thalita Morais