Proof of evolution that you can find on your body

Your body is a temple, but it’s also a museum of natural history. Look closely and you’ll see parts that aren’t there because you need them but because your animal ancestors did. No longer serving their previous function but not costly enough to have disappeared, these remnants of our deep history only make sense within the framework of evolution by natural selection. With your arm on a flat surface, push your thumb against your pinky and tip your hand slightly up. If you see a raised band in the middle of the wrist, you’ve got a vestigial muscle in your forearm. That tendon you see connects to the palmaris longus, a muscle that around 10-15% of people are missing on one or both of their arms. It doesn’t make them any weaker though. There’s no difference in grip strength. In fact, it’s one of the first tendons that surgeons will take out so they can use it in reconstructive and cosmetic surgeries. You can find the palmaris longus across mammal species, but it’s most developed among those that use their forelimbs to move around. In primates, that means the muscle is longer in lemurs and monkeys and shorter in chimps, gorillas, and other apes that don’t do a lot of scrambling through trees. It’s not the only leftover muscle that we've got. Look at the three that are attached to our outer ear. We can’t get much movement out of these muscles, especially compared to some of our mammal relatives who use them to locate the sources of sounds. Presumably this would have been quite helpful for early nocturnal mammals. In humans, you can still detect the remnants of this adaptation with electrodes. In one study researchers recorded a spike of activity in the ear muscle cells in response to a sudden sound. Not enough to move the ear, but detectable. And you can probably guess the location of the sound based on the results - it came from a speaker to the left of the study subjects. So this is their left ear subconsciously trying (and failing) to pivot toward the sound. You can see another futile effort by our vestigial body parts when you get goosebumps. When we’re cold, tiny muscles attached to our body hairs contract, pulling the hair upright which causes the surrounding skin to form a bump. For our furry mammal relatives, the raised hair increases the amount of space for insulation, helping them stay warm. Birds can do this too. you’ve probably seen a puffy pigeon on a cold day. Adrenaline is one of the hormones involved in the body’s response to cold temperatures, and it’s also part of the fight or flight response. So it helps some animals appear larger when they’re threatened. And it may be why surprising and emotional turns in music can give some people goosebumps. And then there’s our tail. At the end of our spine are a set of fused vertebrae - some people have 3, some have 5. We call it the tailbone. It now serves as an anchor for some pelvic muscles but it’s also what’s left of our ancestors’ tails. Every one of us actually had a tail at one point. When the basic body plan is being laid out at around 4 weeks of gestation, humans embryos closely resemble embryos of other vertebrates. And that includes a tail with 10-12 developing vertebrae. In many other animals it continues to develop into a proper tail. But in humans and other apes, the cells in the tail are programmed to die a few weeks after they appear. Vary rarely though, a mutation allows the ancestral blueprint to prevail and a human baby will be born with a true vestigial tail. The most adorable vestigial behavior is the palmar grasp reflex, where infants up until they’re about 6 months old have this incredible grasp on whatever you put in their hand. There’s a similar reflex for their feet. I wanted to show you this great piece of footage from the 1930s where they demonstrated this behavior. These babies are only 1 month old and you can see that their inner monkey can support their entire weight.

Channel: Vox

Views: 32,872,183

Rating: 4.629703 out of 5

Keywords: evolution, human evolution, proof of evolution, vestigial trait, human tail, vestigial, vestigial tail, vestigial muscle, leftover muscle, vestigial body parts, coccyx, tailbone, tail, goosebumps, why do we get goosebumps, natural selection, charles darwin, creationism, creationist, intelligent design, biology, zoology, mammals, vox, vox.com

Id: rFxu7NEoKC8

Length: 3min 55sec (235 seconds)

Published: Thu Mar 17 2016

Reddit Comments

[u/Honda_TypeR]

TIL evolution stole my Palmaris Longus >:(

[u/Glacier_Taste]

When I was in the Army and stationed in Florida there was this really nasty strip club. There was a stripper there that had a vestigial tail. She seemed to make pretty good tips.

[u/AppleChiaki]

When babies are born with a tail, is it functioning in any way, or broken?

[u/jmuch88]

I know evolution is real, all I need to do is look down and see how much smaller my penis is than everybody else. Smaller is the future right guys?

[u/BdonMack]

That poor cat

[u/sunommy]

I have those tendons in both arms. What does that mean?

[u/DrColdReality]

My favorite has always been the recurrent laryngeal nerve, the nerve that runs from the brain to the larynx. Now you'd think that in humans, that would be a pretty short trip.

And you'd be wrong.

In fact, the RLN runs from he brain, down to the vicinity of the heart, underneath the carotid arch, then back up to the larynx. And that's true for all animals who have the nerve. In giraffes. it's typically in the vicinity of 15 feet long.

The reason why it loops the way it does is because modern animals with the RLN all evolved from an early fish that had it, and in the fish, the shortest path from brain to larynx WAS under the heart. As evolution proceeded, the shape of the animals changed greatly (particularly with the development of a neck, which the fish lacked), but the RLN just got longer, because that's MUCH easier for evolution to do than re-routing a nerve.

[u/LaTank22]

Science is a LIAR sometimes https://www.youtube.com/watch?v=LJDgVlv55Uw

[u/Pancake_Lizard]

The only proof I care about.