ExtinctZoo - We're Evolving Backwards

Episode Date: April 12, 2025

300,000 years isn't exactly a long time in the grand scheme of things. And yet it was long enough for us to go through some pretty peculiar "changes"...

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You win? Details at Yamava.com must be 21-20. Please gamble responsibly. Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion. Each and every single one of the approximately 8 billion people on Earth today are considered Homo sapiens. The only species of the genus Homo that is still standing after 2.8 million years of existence. With our specific species having been present for just about 300,000 of those nearly 3 million years,

so less than a blink of an eye by universal standards, but a longish time nonetheless. In this long, yet not so long time frame has created ample opportunity for change. and change we have since those very first days on Earth. And actually, there is probably a lot more differences between us and the very first modern humans than one might think. Now many of these differences are extremely minute and barely recognizable, with some being invisible to the naked eye, while other changes have come but then gone.

And what I mean by this is that in some ways we are now more alike to the first people than other groups of humans from, say, 50,000 years ago were. And this is nicely demonstrated by something that has greatly changed through time, but is now reverting to how it once was, our heights. It's a common misconception that humans have always been getting taller, and instead, in reality, height has been a wild roller coaster, and for the better part of the last 100,000 years, we've been on a downward trend. And not to mention that while getting shorter, we've also gotten smaller proportionally,

and one of the biggest changes became first noticeable roughly 10,000 years ago, when heights suddenly dropped by about 10%. And researchers believe that this may have been tied to dramatic shifts seen in the climate, and our adoption of agriculture, which in the early days result in restricted diets and malnutrition, and thus stunting our growths. And then additionally, the presence of livestock introduced new diseases, which took a toll as well. And it's only been since very recently, though we've started to reverse this trend, getting taller and bigger once more thanks to richer diets and health care following the Industrial Revolution. And so far we've made a remarkable comeback,

rivaling heights not seen since 9,000 BC. But on the contrary, something that apparently has not reverse yet in any visible ways is our bones, which seem to be considerably lighter and weaker than those seen in the earliest sapiens. Specifically, a team found that the amount of porous bones in recent modern humans might be just one-half of what it used to be, with the earliest of our species having bone densities and robustness much closer to what was seen in more stocky homos like the Neanderthals, or even earlier hominens. And this darling drop is likely resulted in a stark limitation to our power output, as our bones cannot take the stress that they used to. and is likely partially behind the rise of bone-related diseases, like osteoporosis.

Now you might be wondering, why has this happened, especially considering that our diet is now pretty good. And the main suspect behind this development is actually quite clear to researchers, and that is the dramatic difference in human lifestyles of today versus back then, with two distinct pulses or switches being seen in recent history. The first one again had to do with the adoption of farming, which led to less nomadic hunting, meaning people didn't need to be built for taking down absolute units of animals like they did before, having a much less physical lifestyle. And then the second, much more recent hit to our bones,

came within the last 100 years or so, as truly sedentary lifestyles have become much more common thanks to 9 to 5 jobs and other functions of complex society. And what's interesting and quite concerning is that the damage seems in some ways to be permanent. And I mean this in the sense that everyone all over the world, at all stages, appear to have weaker bones now. And surprisingly, the team didn't even see improvements in groups

which were more active, and only time will tell how this trend continues to have an impact. And counterintuitively, while our bones have gotten smaller, our bodies have gotten heavier through the worldwide increase is seen in BMI, which unsurprisingly, is chalked up to lifestyle changes once again. And something else, which has only gotten worse over time, it may come as an alarming surprise, is our shrinking brains. Compared to the earliest humans, and especially those from a couple thousand years ago, our brains have gone smaller and smaller, and the modern person's noggin is about 12% smaller than the size of one during the last glacial cycle, i.e. about 17,000 years ago or so. Additionally, it's thought that our brains have decreased

by 100 to 150 cubic centimeters compared to those of earlier humans. Now, this whole dilemma has actually been somewhat of a debate, as in 2022, a group had declared said shrinking, and then shortly afterwards, someone else said, no, that's not happening. But then in In 202023 and 24, separate studies came out which have concluded that the shrinking has really happened. Yet exactly when, where, or why remains unclear. But both seem to agree that the biggest decreases only took place in the last few thousand years, while the trend as a whole appears been going on for far longer. And some pretty interesting ideas have emerged on why exactly this happened,

with one of the more colorful ideas being the self-domestication hypothesis. Which sounds weird, but let me explain. Now, you may not know this, but domestication. animal brains are about 10 to 15% smaller than their wild counterparts, possibly due to less threats and them being more tame and social, and thus requiring in general less brain power for stuff normally associated with survival. And so the idea is that this has applied to us as well, with the hypothesis saying that as we built complex societies, it was better to be more docile, which compiled then on top of the new lack of threats, which ultimately resulted in our

brains cutting down a size or two. However, the criticism to this is that the timing of when the complex communities arose doesn't line up at all for when our brains actually began to dwindle in size. So most have thrown this idea out along with the next one, the know-it-all hypothesis, which suggests that as societies began and people started to become more specialized, they no longer need to know how to do everything, and thus again leading to a size reduction. I mean after all, in modern society, you no longer have to worry about trying to survive a predator attack or how to hunt, forage, bring down an elephant, and so on and so forth. But again, this idea does have a bit of a timing.

issue between these changes in the brain and the changes in our lifestyle. And therefore, the currently most supported, or rather least contested hypothesis, is energy preservation. Basically, the world of today is much warmer than it was not so long ago. In seeing how our brains are energy burners, accounting for 2% of our body mass, but consuming over 20% of our resting energy, it's possible that they got smaller in order to better dissipate heat and reduce heat output. But again, nothing is conclusive. But regardless of the hypothesis, it's definitely true that our brains have shrunk. So naturally, you may wonder how all this impacts our intelligence. And the answer to that is unfortunately, no one has conclusively said anything on this front.

But what scientists have said, or at least wondered about, is how current and future warming temperatures may continue to impact this trend. Especially since this time around, we also have technology, which has led to somewhat dependence on it, and not so much on ourselves. Which is then to say if the self-domestication hypothesis is at least partially correct, then things aren't looking too good. And funnily enough, another change has yet again something to do with our brains. But this time the shape, as somehow the shape of our brains is not what it used to be. Back in the day, brain cases were more elongated or stretched out, while now our brains are more globular, so in other words, round. Now, and contrary to previous things mentioned, this does not seem to be a change that is happening right as we speak,

but rather something that took place a long time ago, with the current belief being that our brains reached their present shape between 100,000 and 35,000 years ago during the late Pleistocene, with earlier sapiens having more archaic, elongated brain cases. And within this rounding trend, it seems that two big changes occurred with our parietal and cerebellar regions, with them essentially bulging out. And this coincidence has led to the idea that globular brains developed to improve the function of these two areas, which is actually good news for us. As together, these areas of brains are associated with many positive things, including planning, self-awareness, memory, tool use, motor function, language, and social cognition, among many other things.

So basically things we all could probably use more of. In continuing the trend, it does seem that our heads really took the brunt of human changes, as another one which has popped up regards not our brains, but our teeth and jaws. Today, in many societies, strong-defined jaws are seen as a good thing. And perhaps this is because they're coming more and more of a rarity, seeing that jaws are now smaller than ever before. And actually, Homo sapiens as a whole have been developing smaller jaws and teeth compared to earlier Homo species regardless.

But it's only been in the last 10 to 30,000 years that the speed of these changes has rapidly picked up. And researchers think that there are a few reasons behind this. Firstly, in the account of the trend of things getting smaller overall, our jaws have shrunk proportionally. But then, in addition to this, our vastly different diets and lifestyles today are major players as well, with special emphasis being on the diet. Thanks to the agricultural revolution, and in recent times the rise of fast and processed foods,

diets had never before been made up with so much soft food, leading researchers to think that the lack of harder stuff has made her jaws weaker and smaller. And this has actually been replicated in research by giving animals soft food diets and studies, which of surprise surprise found that yes, it did make their jaws shrink. And what's more is that our ancestors did unsurprisingly not have nice beds to sleep on, just hard surfaces, or at least harder than current beds, which might have actually actually. benefited them as it would have helped keep their mouth closed when sleeping, which as a result leads to a better developed jaw. And one of the biggest drawbacks of these changes for us has been that while our jaws and teeth have both shrunk, our jaws have done so at a much faster rate, and thus leading to less space for teeth and a massive increase in certain ailments,

like impacted wisdom teeth, misalignment, and pretty much any other general teeth-related issues. And of course, with smaller recessed jaws, you now also have a smaller airway, which in turn can result in a condition called sleep apnea, which is basically where you stop breathing your sleep intermittently. And let's just say, that's not good. Now, fortunately, we are finding some ways to counter this, mainly in adolescence. But if this does freak you out, take a deep breath and chill. And I mean this literally, is that's another thing that has changed in humans of 2025. We've gotten colder.

This all started back in 1868, when a German physician stated that the normal human temperature was 98.6 degrees Fahrenheit, which then went on to become a cornerstone in medicine. But then, not so long ago, a new study found that this number was not only off, but quite some ways off, finding that actually the normal temperature for humans was closer to 97.9 degrees Fahrenheit. And this led to a question of how the German doctor had been so off, and prompted a study which analyzed 200 years in medical records. And the conclusion was that not only have humans chilled out, but they keep doing so every year,

as they found that body temps have fallen but roughly 0.05 degrees Fahrenheit every decade. But this brings up the question of why. And we're not 100% sure, but the reason behind this, according to one researcher, is that it's possibly due to our improved living standards that is in turn decreased the amount of viruses, infections, and diseases that people live with, and thus reducing the total amount of inflammation in people, which in itself is known to raise our internal temps.

In seeing that diseases were way more frequent throughout all of human history, including when we first appeared, scientists think that they, too, were considerably warmer than us. So in other words, who knows how hot early modern human human, humans were. Furthermore, the researchers who put out the study believe that due to technology, which is presumably going to continue getting better, we can expect ourselves to become even colder, but by how much is unclear. Now, another massive change, which can definitely be seen as beneficial, is regarding our age, because as a whole, humans have much longer lifespans

than our ancestors. And though it's hard to say with complete certainty how long the first people lived, the lifespan for the entire Paleolithic is often chalked up to be between 22 and 33 years old. or an average of 27.5. While now, it stands at 73.2, so more than two and a half times greater. And to just put this in a perspective, that's pretty much like taking a group of bears, sticking them on an island, and then coming back to just find that they now live to 65 years old. And as you can probably imagine, this change has primarily come from our advancements in technology,

which has aided our health and has allowed us to better avoid and conquer threats. However, technology is somewhat a double-edged sword, because it has also brought some changes which are very negative, such as poor eyesight from constant screen use, cancer from pollutants, diseases like diabetes and osteoporosis, and many, many more. And ultimately, many of the recent changes in ourselves do boil down to recent technological and cultural developments. But one thing that did not is diversity, specifically phenotypic diversity. The first humans were likely much less diverse in appearance and traits than we are now,

seeing that they, one, lived in a much smaller area, two, had smaller populations, and three lived in environments that were more homogenous. But then, some tens of thousands of years ago, or possibly even longer, certain groups finally decided to take the leap out of Africa, likely spurred on by climate change in droughts, and thus beginning an explosion of phenotypic diversity due to new and varying environmental pressures. Over time, these groups would go in to populate every other continent on Earth,

minus one, where in the presence of very different environments developed adaptations that weren't seen prior. And then to add on to this, the Earth overall has undergone some pretty big changes in just the last 300,000 years, including the last glacial maximum, which again brought pressure upon humans and thus more adaptation. And all of this combined resulted in changes in evolutionary pressure on certain traits. One of the more obvious and well-known ones is pigmentation, as in areas with less sunlight, lighter skin developed to better allow the penetration of UV rays

and thus improve vitamin D synthesis. Meanwhile, some propose that eye color too has been impacted by sun level. If certain researchers found that blue eyes, for example, became a thing as it increases intraocular light scattering, which in turn suppresses melatonin and perhaps reduces the increased rate of depression seen when someone lives in a northern latitude and experiences shorter days. Then on top of skin color and eyes, straight hair popped up in some groups for heating purposes, as it allows for hair on the neck and scalp, which in turn helps keep the area warm and allows cold moisture to be removed more easily. Also regarding the eyes again, the epicanthic fold seen among eastern and northern Asian populations has been touted by some as being an additional adaptation for protecting the eye from forceful snowfall

and helping diminish the amount of sun glare that one experiences. And honestly, just regarding our overall heads, we see various adaptations in each and every group, which has helped them better to adapt to their environment, resulting in some people having flatter faces, different nose shapes, body builds, and so on. Now, a lot of the traits that I mentioned are seen across massive populations of people, but then we also have those that are very specific. Take the Samabajau, for example, a group native to Maritime Southeast Asia, who typically live a seaborne lifestyle and have developed traits to aid them in it.

Namely, their spleen's are much larger than normal, being about double that of those seen in their neighbors. And while not necessary for survival, because yes, you can't actually live without your spleen, spleen do store oxygenated blood, which definitely helps out if you're trying to hold your breath, for long periods of time. And coincidentally, many marine mammals in general tend to have enlarged spleen, and the Bajiao people on average can hold their breath for up to five minutes while diving down,

which just for perspective is about five to ten times longer than the average human. And then in a somewhat similar situation, groups that live in high altitude, like Tibetans and Andeans, show traits designed for living up in the mountains where there is less oxygen, resulting in traits allowing them to survive in this environment,

including showing adaptations to their hemoglobin, decreased resting heart rates, and increased lung capacity. And what makes this all more fascinating is that most of these features are seen even in people from the group that don't end up actually living in higher altitudes. So in other words, they're built different. However, with all that said, phenotypic diversity is also substantial and genetically, arguably greater, among populations that remained in Africa. In fact, the continent contains the highest levels of human genetic variation

than anywhere else in the planet, and evolutionary pressure here is very much alive and well, just like the rest of the world, and has continued to derive significant adaptations even within the last 10,000 years. One such example is the sickle cell trait, which alters red blood cell shape to offer protection against malaria, and this trait is found out rates of between 10 to 40% in Western Africa, despite it only having evolved some 7,000 years ago or so. Now, with us all said, it is also highly likely that the earliest humans had their own fair share of odd features based on their environment, climate, and genetic pools.

And speaking of genes, that's a whole other area we could talk about, is ours are certainly quite different and always changing. Off the bat, more genetic diversity exists now than ever before, due to the massive increase in human population. While then additional factors like Neanderthal DNA and other extinct human admixture, all just go to further increase the diversity of our genomes. And so with all these factors take into account, you can probably understand why overall,

we are surprisingly different than the people who walked the earth 300,000 years ago. And perhaps poetically, it has changed itself that is the last thing to talk about, because even how we change is different today than it once was. Never before has an animal been able to use technology to seamlessly spread out across the entire world and basically inhabit any climate it wants to, while simultaneously using technology in pretty much every other part of their lives as well. And honestly, it's basically impossible to tell how our dependency on technology will have a long-term impact on our future, especially when considering that the crazy developments have only started happening

not so long ago. But I guess we'll see and cross our fingers for the best. And just for good measure, let's cross them tightly. Thanks for watching and until next time. Ambition comes in all shapes and sizes. At First Citizens Bank, we roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank. Stitch Fix. Stop shopping. Get styled. Not today's sweatpants. Somebody's wearing jeans that fit. Wow! No photos, please. I'm just a regular dad who happens to have a stylist.

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