The Insane Biology of: Humans

our planet is full of animals with absolutely crazy anatomical adaptations cheetahs can run up to 75 miles per hour or 120 kilometers per hour frogs can survive being frozen alive cows have four stomachs and octopuses have nine brains compared to all these other animals humans might seem like we're lacking we're not the best jumpers climbers or sprinters and we definitely can't hibernate or regrow our limbs if they get cut off and yet humans occupy our own very special part of the evolutionary tree so much so that we barely even consider ourselves animals because when you

take a step back humans are incredible and you might even say we are downright weird there is no other animal quite like us we have so many adaptations that are completely unique to us there are the ones we use on a daily basis and largely take for granted our Nimble fingers big brains and the ability to walk on two legs these assets have allowed us to create mega cities and occupy nearly every habitat across the world as we've been exploring in our nebula original series becoming human but then there are the adaptations that we don't

see every day adaptations that some of us have but never use or adaptations that only select groups of people have from throwing to diving to high altitude climbing when properly trained humans are one of the most incredible athletes of the animal kingdom [Music] if you're a fan of baseball you'll know that one of the most valuable players on any team is the pitcher the very best of them can accurately throw balls at tiny targets and reach speeds over 105 miles or 169 kilometers per hour these throws are so intense that since 1862 nearly 200 batters

have died after being hit in the head or the chest while this is a tragic example of risk in sports we normally think of as safe it's also evidence of a trait that no other species possess the ability to throw projectiles and kill targets and it's not only professional pitchers who have such strong arms young boys between the age of 8 and 14 who had moderate levels of little league training could throw two times faster than a chimpanzee even though chimps are about four times as strong as young men when controlling for size you'd think

that given the way chimps and other Apes going through the trees they'd have much better throwing arms than we do but several things happened to our physiology during Evolution that separates us from the rest of the primates first the length of our waist expanded allowing our torso to rotate independently from our hips next our shoulders have developed a lower position on the Torso and the glenoid joint where the collarbone meets our shoulder socket points out to the side rather than upward like in chimps this means we can turn our arms into levers finally our humerus

the bone in the upper arm has a slight twist in it allowing us to rotate the arm even further back putting all three of these elements together creates an incredible throwing machine twisting the arm back stores energy in the tendons and ligaments crossing the shoulder this energy catapults the arm forward and actually creates the fastest motion the human body is capable of producing and all three of these factors appeared in the fossil record almost 2 million years ago with our hominid ancestor Homo erectus at the very same time we start to see evidence of more

intense hunting in the fossil record in the form of butchered bones and simple stone tools suggesting throwing played a major role in shaping how we got food and maybe even how our brains grew so large unfortunately not all Spears would have fossilized but some certainly have wooden spear points as old as 300 000 years have shown up in archaeological digs in Africa Germany and England while some ethnographers argue that these Spears were too heavy to go very far as projectiles a more recent study conducted with trained Javelin athletes found that these Spears can be thrown

farther than 50 meters and at speeds ranging from 12 to 21 meters per second at such high speeds and distances it was more than possible for ancient humans to take down large prey from a relatively safe distance this throwing ability may have also been used for fighting between humans as well which we can still see today whether hunting or fighting was the key to unlocking our killer arms it's clear that this adaptation has had a huge impact on how we live play and compete but our early ancestors weren't only expanding their abilities in hunting on

land they were also foraying into a territory no other primate had ever been one of our wildest adaptations is one that was born simply out of a need to not drown it's an adaptation that is not unique to humans but one that humans have learned to manipulate for incredible athletic purposes in 2007 a freediver reached a depth of 214 meters holding his breath for longer than three minutes while he plunged deep into the ocean the record for stationary breath holding is perhaps even more incredible a full 24 and a half minutes without any air freedivers

like this are making use of the mammalian dive reflex a set of physiological changes that take place in the body in response to a mammal being submerged in water and holding its breath whether that's done voluntarily or not the dive reflex in humans begins when you submerge yourself specifically your face in cold water while holding your breath the cold water triggers the trigeminal nerve to send signals to the brain stem to initiate the survival response first the heart almost immediately enters bradycardia a dramatically slowed rhythm then the capillaries in the fingers toes hands and feet

constrict and blood flow is directed to the brain and heart as the oxygen level in the lungs drops more and more carotid bodies send out even more signals to the brain stem to further constrict blood flow in the extremities in order to save it for vital organs in a life or death situation this response can keep enough oxygen flowing to the organs that need it most to keep you from dying but there's even more happening with our organs the spleen which helps filter blood also controls the level of red blood cells white blood cells and

platelets circulating our bodies when humans go underwater the spleen responds by Contracting to squeeze out a burst of oxygen-carrying red blood cells this is another important survival mechanism however when you compare the spleen sizes of different populations in the world you start to see that humans have taken this don't die mechanism and turned it into a badass ocean superpower take the badge out people for example who live around Indonesia the Philippines and Malaysia they survive by collecting shellfish off the sea floor and are known for their extraordinary ability to hold their breath they dive repeatedly

for about eight hours a day to depths of over 70 meters for several minutes at a time compared to nearby non-diving populations the bajau have spleens that are 50 percent larger and this anatomical Quirk isn't just a consequence of repeated diving the bajao who don't do as much diving on a daily basis still have a larger spleen meaning it's an evolutionary response to this group's diving lifestyle but researchers think it's not just the bajau who have leveraged the mammalian dive reflex to get give themselves a leg up while hunting perhaps our entire species has been

foraying into the Seas for a long long time just look at our other primate relatives for context gorillas and chimps have the same diving reflex that we do but they are nowhere near as comfortable or proficient in the water in 1960 marine biologist Aleister Hardy proposed The Aquatic ape Theory suggesting that early humans foraged for aquatic foods and spent hours at a time in the water he pointed to things like our furlessness and the layer of body fat under our skin that other primates don't have but the theory became something of a catch-all an umbrella

argument used to explain many elements of the human body it was largely dismissed by the archaeological and anthropological communities that said there is evidence in the fossil record of our close relationship with aquatic environments a homo erectus site in Northern Kenya holds the butchered remains of turtles crocodiles and Fish dating back nearly 2 million years and a number of Neanderthal skulls have been found to have ecstosis bony growths in the ear canal that forms with repeated exposure to cold and wet conditions in modern humans they're often found in Surfers divers and swimmers and even if

free diving didn't shape our Evolution from the beginning there's certainly no denying that people today have learned to push the limits with the Aquatic adaptations we do have for those of us who can't imagine diving three meters down or holding your breath for more than a minute it's worth mentioning that all of these skills can be improved with some training leading researchers to suggest that maybe we are all better suited to the Aquatic world than it might initially seem while we might all have some ability to throw a spear or hold our breath and swim

there are some human adaptations reserved for only a select few adaptations found high in the mountains at sea level in cities like Boston or Miami the atmosphere is filled with a comfortable 21 oxygen but as the altitude increases the effective oxygen level begins to steadily drop the percent of oxygen in the air Remains the Same but there are far fewer molecules of it available to our needy lungs above 1500 meters in cities like Boulder effective oxygen dips to 17.3 percent above 2 000 meters it dips below 16 percent and physical activity becomes more difficult and

you might feel way more out of breath than usual above 2500 meters effective oxygen drops to 15 percent and without acclimatizing about 50 percent of people will get altitude sickness which can develop quickly and be life-threatening headaches nausea and shortness of breath are common but in the worst cases fluid can build up in the lungs or the brain can swell both of which can be fatal above 3000 meter effective oxygen drops to 14.3 percent and chronic altitude sickness affects five to ten percent of people who spend months or years there this is a result of

long-term hypoxia it leads to having too many red blood cells which can cause the blood to thicken and increase the risk of blood clots heart attacks and strokes the problem can even result in heart failure in the long term and over four thousand meters effective oxygen drops below 13 percent and for most people without acclimating acute hypoxia is certain this can rapidly progress to the more severe and potentially fatal high-altitude cerebral edema and high altitude pulmonary edema but these risks almost completely disappear for a certain subset of people a subset of people who have historically

lived in three high altitude locations around the world the Tibetan plateau in Asia the Andean atiplano in South America and the samian plateau in Ethiopia these locations range between 2500 to over 4 000 meters in each of these places the human body has adapted remarkably well to harsh conditions but not always in the same way in the Andes and some parts of high altitude Ethiopia Highlanders have more oxygen-carrying hemoglobin in their blood than those who live closer to sea level having more hemoglobin to carry oxygen through the blood system than people at sea level counterbalances

the effects of hypoxia but in Tibet and other parts of high altitude Ethiopia people have far less hemoglobin than the andeons at levels more similar to people who live at sea level they instead have genetic changes that have allowed them to use smaller amounts of oxygen more efficiently for one they naturally take more breaths per minute than people who live at sea level and then on top of that their lungs generate larger amounts of nitric oxide from the air that they breathe this nitric oxide Works to increase the diameter of their blood vessels allowing them

to deliver oxygen throughout their bodies more effectively than sea level people do and of the Tibetans there is one group that uses this natural ability to its extremes the sherpa climbing Community the sherpa are one of the Tibetan ethnic groups native to the most mountainous regions of Nepal Tibet and the Himalayas and of this group those who have dedicated their lives to mountaineering are regarded as some of the most elite mountain climbers to have ever lived Sherpa tenzig Norge was the first person to Summit Mount Everest alongside Edmund Hillary in 1953 and since then Sherpa

records on Mount Everest have not stopped Sherpas hold the records for the most descents to The Summit 26. in fact the top 10 summiters are all Sherpas the longest stay on the summit which was 21 hours which he did without bottled oxygen for reference most people stay for 20 minutes and the fastest Ascent to the summit which he did in 10 hours and 56 minutes this last record is particularly ridiculous to think about the total distance from the South Base Camp to the summit is 20 kilometers with an altitude change of 3 500 meters it

takes most people 6 to 10 weeks to do this climb having to make many shorter up and back acclimating ascends part way up before being able to make the final push to the summit and this guy did it all in 11 hours I don't think I I could even walk on flat ground in a nice environment for 11 hours straight and for most foreigners who have managed to reach the top many many Sherpas were involved in laying ropes ladders and carrying equipment to make it happen a physical burden far beyond just climbing the mountain the

sherpa record Setters are trained seasoned professionals with years of practice and experience boosted by unique high altitude physiology some people even try to mimic this enhanced ability for exercise by training at high altitude but the benefits they get from this strategy are always short-lived only those populations that have a long history of living in high altitude places have genetic changes that allow their bodies to thrive in places where most of us struggle how the human body will continue to change in the future is an open question because Evolution isn't done with us yet just as

we can't fathom what abilities future humans might have so too would it have been impossible for our early ancestors to imagine how far we've come and how very strange the journey has been would our ape-like ancestors have imagined their descendants totally abandoning quadrupedal movement for an upright stance would they have imagined those liberated hands to start crafting complex tools or for communities to create languages and systems so complex that they would one day travel amongst the Stars The evolutionary journey of humans has been a total departure from anything else that has happened on this planet

our story utterly unique even among the primates what makes us so special how did the spinning wheel of evolution land on us to become the ones to dominate the planet this is a topic that's fascinated me for years but I shied away from exploring it on this channel since it's a bit more philosophical and anthropological than what we normally do here but now thanks to nebula we've been able to explore the subject of human evolution in depth with our new nebula original series becoming human thanks to nebula we've been able to take the precious time

to craft a whole new 3D Museum that features in every episode showing you the actual fossils and skeletons of the early human ancestors that were explaining with this stunning imagery the series takes you through the steps of how it is that we became human every sign up makes us happy because it means we can keep bringing you more and better content and if you're looking for something else to watch right now you can watch our latest video about the surprising reason some sharks live inside underwater volcanoes or you can watch real engineering's latest video about

a new way to achieve nuclear fusion