Biological Features Humans Have Almost Completely Lost

Your ear muscles still aim at sounds and move nothing. A single piece of parasitic DNA landed in one gene 25 million years ago and no ape has been born with a tail since. And one broken liver gene killed roughly two million sailors. Here are 10 parts of your body that stopped working and never got removed. Humans retain the auricularis superior, anterior, and posterior muscles, and work by Steven Hackley at the University of Missouri showed they fire toward sudden sounds within milliseconds despite moving almost nothing, with a 2025 Saarland University study finding the superior auricular activates during effortful listening. The palmaris longus, absent in roughly 14% of people and varying widely by population, contributes no measurable grip strength and is routinely harvested as a tendon graft, including in Tommy John surgery. The plica semilunaris at the inner corner of the eye is the remnant of a nictitating membrane still functional in birds, sharks, and cats, now serving eye rotation and tear drainage. Arrector pili muscles produce goosebumps that trap no heat, though a 2020 study from Ya-Chieh Hsu's lab at Harvard published in Cell found the muscle physically bridges a sympathetic nerve to hair follicle stem cells, driving hair growth under sustained cold. Of roughly 800 to 900 human olfactory receptor genes, only about 400 function, and around a third of adults cannot smell androstenone at all. In 2004, Hansell Stedman at the University of Pennsylvania reported in Nature that a two-base-pair deletion in MYH16, dated to roughly 2.4 million years ago, disabled a jaw-muscle protein, coinciding with braincase expansion. The palmar grasp reflex, tested on newborns by Louis Robinson in 1891, lets infants support their own weight and disappears around five to six months. The vomeronasal organ persists as a pit with no functional sensory neurons, no accessory olfactory bulb, and a pseudogenised TRPC2 shared across Old World monkeys and apes. The GULO gene enabling vitamin C synthesis broke roughly 61 million years ago, and scurvy is estimated to have killed around two million sailors between 1500 and 1800. And in 2024, a team led by Bo Xia at NYU published in Nature that an AluY insertion in the TBXT gene around 25 million years ago eliminated the ape tail, reproducing shortened tails in engineered mice. ⏱️ CHAPTERS 0:00 — Number 10: The Muscles That Move Your Ears 1:25 — Number 9: The Disappearing Forearm Muscle 2:45 — Number 8: Your Third Eyelid 4:00 — Number 7: Goosebumps 5:15 — Number 6: Half Your Sense Of Smell 6:35 — Number 5: The Jaw Muscle That Shrank Your Face 8:00 — Number 4: The Grip You Were Born With 9:20 — Number 3: The Pheromone Organ 10:35 — Number 2: Making Your Own Vitamin C 11:55 — Number 1: Your Tail 13:30 — Outro ❓ QUESTIONS THIS VIDEO ANSWERS Why can some people wiggle their ears? Do human ear muscles still respond to sound? What is the palmaris longus? How do you check if you have a palmaris longus? Why do surgeons use the palmaris longus tendon? What is the plica semilunaris? Do humans have a third eyelid? Why do we get goosebumps if we have no fur? What does the arrector pili muscle actually do? How many olfactory receptor genes do humans have? Why can't some people smell androstenone? What is the MYH16 gene? Why is the human jaw weaker than a chimpanzee's? Why do wisdom teeth cause problems? What is the palmar grasp reflex? Can newborns support their own weight? What is the vomeronasal organ? Do human pheromones actually work? Why can't humans make vitamin C? What is the GULO gene? How many sailors died of scurvy? Did humans ever have tails? What is the TBXT gene? Why are babies sometimes born with tails? 🔔 Subscribe for more countdown explainers like this one. 💬 Do you have a palmaris longus? Comment YES or NO 👇 #HumanBody #Evolution #Biology