Proof of evolution that you can find on your body

Summary

This video delves into the fascinating remnants of our evolutionary past. It explores vestigial body parts, like the palmaris longus muscle in our forearm, the underused ear muscles, and the tailbone, once the tail of our ancestors. It highlights how these features no longer serve their original purpose but still persist due to evolutionary processes. The video also touches on human reflexes like the palmar grasp, which connects us to our primate ancestors, showcasing the hidden traces of our animal lineage and the complex history embedded in our bodies.

Takeaways

• 😀 Our bodies carry remnants of evolutionary history, including features no longer serving their original purpose.
• 😀 The palmaris longus muscle in the forearm is vestigial and absent in about 10-15% of people, but it doesn't affect grip strength.
• 😀 Surgeons often use the palmaris longus tendon in reconstructive and cosmetic surgeries.
• 😀 The palmaris longus is more developed in mammals that use their forelimbs to move, such as lemurs and monkeys.
• 😀 Humans have vestigial muscles in their outer ear, which used to help animals locate sound sources, especially in nocturnal mammals.
• 😀 Despite being mostly inactive in humans, ear muscles can still show activity in response to sudden sounds.
• 😀 Goosebumps are a vestigial response where tiny muscles pull body hairs upright, a leftover feature for insulation in mammals.
• 😀 Adrenaline causes goosebumps both as a response to cold and as part of the fight-or-flight reaction to danger.
• 😀 Humans have a tailbone (vestigial tail), which is the remnant of a tail that all vertebrate embryos initially develop.
• 😀 Most humans have a tailbone made of fused vertebrae, with rare cases of babies being born with a true vestigial tail.
• 😀 The palmar grasp reflex in infants, where they can grip objects with great strength, is a vestigial behavior from our primate ancestors.

Q & A

What is the significance of vestigial muscles in humans?

Vestigial muscles are remnants from our evolutionary ancestors. While these muscles no longer serve their original function, they persist in the human body because they are not costly enough to be eliminated by natural selection.

What is the palmaris longus, and why is it important?

The palmaris longus is a vestigial muscle in the forearm that some people lack. It connects to a tendon visible when you push your thumb against your pinky. It is used in reconstructive surgeries and does not affect grip strength.

How is the palmaris longus muscle different across species?

The palmaris longus is more developed in mammals that use their forelimbs to move, such as lemurs and monkeys, and less developed in species like chimpanzees and gorillas that do not engage in tree scrambling.

What is the role of the small muscles in our outer ear?

These muscles were once used by our mammalian ancestors to detect the source of sounds. In humans, their function is much reduced, but they can still show activity in response to sounds, indicating a vestigial function.

Why do humans get goosebumps, and what does it have to do with our evolutionary past?

Goosebumps occur when small muscles contract around body hairs, causing them to stand upright. In our animal ancestors, this response helped increase insulation by raising fur. It can also make an animal appear larger when threatened.

How are goosebumps related to the fight-or-flight response?

Goosebumps are part of the body’s reaction to cold and stress. The hormone adrenaline, which is involved in the fight-or-flight response, can trigger goosebumps, causing a person to appear larger and potentially intimidate threats.

What is the tailbone, and what is its evolutionary origin?

The tailbone, or coccyx, is a remnant of the tail that our primate ancestors once had. During human development, a tail forms but typically recedes after a few weeks, leaving behind the tailbone.

Is it possible for humans to be born with a functional tail?

Yes, in rare cases, mutations can cause a human to be born with a true vestigial tail. However, this is a rare occurrence, and most human embryos lose their tail during development.

What is the palmar grasp reflex, and why is it significant?

The palmar grasp reflex is an instinctual behavior where infants, up to about six months old, can strongly grasp objects placed in their hands. This is a vestigial trait from our primate ancestors, where such reflexes helped babies cling to their mothers.

Why is the palmar grasp reflex important for understanding human evolution?

The palmar grasp reflex highlights our evolutionary heritage, demonstrating how human infants retain primitive behaviors that were crucial for survival in earlier mammalian species. It shows a link to primate ancestors who needed these reflexes to cling for protection.