Homo Erectus: The First True Humans in Human Evolution

[00:00:00]What defines a human?

[00:00:10]We're obviously hairless, bipedal apes. We're  good at running, at least some of us. We have a very sophisticated language, not just one of them  hundreds maybe even thousands depending on how you define it. We're obligate tool users. We basically  can't accomplish anything without them. We're creative. Our tools and our language have allowed  us to express really complex and abstract ideas, and of course we have spread  across the entire globe.

[00:00:39]I believe we can trace all of  these defining features back to owners of skulls like this. This is Sangiran  17, or at least a plastic copy of it.

[00:00:49]It was excavated on the island of Java, Indonesia  and it belonged to someone who lived about 1.5 million years ago. Today we call  these hominins homo erectus.

[00:01:02]In my opinion they're the first hominins who truly  deserve to be called human. From their biology, to their technology, their globe spanning  reach, maybe even artistic and linguistic abilities, these chaps and chapettes were an  absolutely huge leap forward in human evolution, and today I just want to break down what  it is that is so special about them, why I think they are the first true humans.

[00:01:44]Homo erectus is a really well studied fossil specimen but despite that its origins  remain basically unclear. After a major glaciation 2.5 million years ago there were multiple  species of early homo and australopithecus that all overlapped in time in east africa, but  the identities of these species are still debated.

[00:02:08]Homo habilis has been considered for a long time  the first in our genus homo because it was found with the stone tools, but some anthropologists  think it's actually too primitive to really be in our genus, to really be homo and uh is  more likely some sort of australopithecus.

[00:02:27]Homo rudolfensis seems to be a larger version  of habilis but whether or not it's a distinct species is still up for debate as well.  Most anthropologists recognize habilis and rudolfensis as being distinct but because  it's still debated it's easier just to call them both early homo. With the separation  between australopithecines and early homo still kind of unclear it's hard to know  exactly when and where homo erectus originated.

[00:02:57]The oldest homo erectus fossil that the scientific  community agrees upon are around 1.9 million years old and come from Koobi Fora in Kenya, overlapping  in time with both habilis and rudolfensis, but one of the most famous early  homo erectus fossils actually comes from outside of Africa from Georgia  and dates to 1.8 million years ago.

[00:03:24]Incredible! Really old!!

[00:03:26]This showed that homo erectus had made long  migrations out of Africa very shortly after it evolved and that it didn't need a big brain  to do it. It really was an incredible discovery.

[00:03:39]"whoa steady on" I hear you say. Small brains?  Stefan these are supposed to be the first humans.

[00:03:45]What are we if not, you know, big walking brains?  Well within the species that we call homo erectus there is actually a ton of variation. They lived  for 1.8 million years across three continents.

[00:03:58]There's so much variation that you might find  them referred to as a different species like homo ergaster. We're gonna ignore that convention  today, it's perfectly acceptable to lump them all in as homo erectus. Despite this variation  and this huge time span that they were around, there are some key uniting features that  we can point to as definitively erectus.

[00:04:20]Compared to early homo and australopithecines they  had larger bodies, smaller teeth, smaller jaws, but the first major change were these big brains.  Early erectus, who we could call homo ergaster, like the ones found in Dimanisi, Georgia  only had a brain size of about 540 cc's.

[00:04:41]Bigger than a chimpanzee but not by a lot. If  we compare that to erectuses like Sangiran 17, that lived half a million years later in  Indonesia, they had brain sizes of about 1200 cc's. To put that into perspective a modern homo  sapiens, like me or you, might have a brain size of around 1350 cc's. So within that half a million  years they had basically tripled to modern levels.

[00:05:07]That's huge! That's really significant!

[00:05:10]Erectus was also the first hominin that had the  ability to run. We can tell this from their short bowl shaped pelvises. Mathematical models  indicate that they may have been able to run for five hours straight, which is way  beyond my abilities in my current state.

[00:05:27]Obviously you can't run that long if you're  covered in hair, it's kind of hard. Interestingly, studies of our genetics have shown that  the genes for dark skin evolved around 1.2 million years ago meaning that our skin  had been exposed to the sun by then. So erectus was almost certainly the first kind of  hairless hominin. These traits are obviously abundant across the entire world, across our  entire species, so you might be inclined to think "uhhh yawn fest, big deal" but uh in reality it would be hard  to underestimate their importance.

[00:06:03]Together all these things signal major  changes to the morpho-behavioral package that homo erectus had. Homo erectus didn't  just look like an upright walking chimpanzee they would have looked much more  like us. They would have walked further to get their food and the food  they were eating was much higher quality, to fuel this huge brain expansion. Erectus  wasn't just an upright walking ape they'd have lived a lifestyle that was familiar to  humanity for the rest of the paleolithic.

[00:06:35]It's obviously difficult for us to say exactly how  homo erectus went about hunting animals but we can tell from the bones that they left behind and  the marks on them that they were getting primary access to the most nutritionally dense parts of  the animal. They weren't just scavenging. And that these were big animals too, really big animals  like hippos and giraffes things like that. So, however they went about it they were certainly  capable of some pretty advanced hunting skills.

[00:07:07]Now running and hunting is all well and  good, definitely a major leap forward in our evolution but a defining feature of our  morpho-behavioral package as homo sapiens is language. So could homo erectus talk? That's  kind of a difficult question to answer.

[00:07:26]For language to exist of course there needs to  be certain biological preconditions that have to be met. The first would be larger brains which  as we've discussed later erectus certainly had, but just because it's big doesn't mean it's  wired correctly for language. You also need the brain to function at a much higher  cognitive level. Now believe it or not, the guy sat in his garage talking to a spoon  is not Mr.brain scientist, but according to the source in the description the evolution of  genes srgap2c and srgap2d, I had to look at my notes there for that one, these genes in the lab  were associated with higher brain connectivity.

[00:08:15]Intriguingly it seems that these genes  evolved at the same time erectus appeared in the archaeological record. Now I'm not saying  erectus had a language as complicated as ours, far from it, but like all things language is  a trait that we have evolved to have. It's unlikely that it appeared fully formed just in  us homo sapiens. It's not unreasonable to think that the building blocks of language could  be found in homo erectus, that they had some sort of linguistic capability maybe some sort of  a sophisticated sign language say. I don't know it's hard to say for sure because words  and gestures aren't uh preserved in the archaeological record but if we look at the tools  they left behind, the technology they left behind, it certainly indicates that these chaps  and chapettes were very smart indeed.

[00:09:14]The technology that homo erectus is most known  for and one which likely gave them a distinct evolutionary advantage, is fire. The main idea  is that earlier hominins spent a ton of time and energy digesting raw meat and difficult to  eat foods. It's why the australopiths have such thick sturdy jaws. But once we developed fire it  did much of this work for us. It allowed our guts to take it easier and our brains to absorb that  extra energy, allowing them to grow to the size that they are now. This is a great theory, it's  a very nice theory. There's a serious problem with it though in that the earliest evidence for  controlled fire that most archaeologists would agree with is only 780,000 years old, from Israel.  Much later than when we see big brains appear in the fossil record. Earlier possible sites  are being unearthed, such as Koobi Fora, in Kenya, which could push back the evidence for  controlled fire use to 1.5 million years ago.

[00:10:22]The only problem is it it's just difficult to say  for sure. Humans don't have a monopoly on starting fires, they can occur perfectly naturally on  their own. Considering the sparse evidence for deliberate fire use, it does raise interesting  questions about how they expanded into a new territories, colder  territories. How did they do this?

[00:10:46]oooff made jump then.

[00:10:48]How did they do this without fire to keep  them warm? Perhaps they huddled together?

[00:10:54]Perhaps they had some form of rudimentary  clothing? Perhaps both of those things?

[00:10:59]Perhaps neither? Maybe our ancestors weren't even  cooking with fire at all? Analysis of soils from Olduvai Gorge, dated to around 1.7 million years  ago, suggest that the area might have had natural hot springs. This led the investigators to  wonder, what role did this hot water play in our evolution? Instead of roasting meats and  plants and seeds, were we boiling them instead?

[00:11:28]I, I absolutely love this idea. I can't help but compare it to those Japanese monkeys  that live around those hot springs.

[00:11:39]Just, just imagining like an ancient homo  erectus sitting in the hot spring, chilling, just having an absolutely fantastic time the same  way that you or I would. It's so humanizing! I, I hope that that was how our evolution went down,  that we evolved in hot tubs, I really hope that.

[00:11:59]Whilst we're on the subject,  there is another big debate around homo erectus and water. Now obviously homo  erectus or the hominins that left Africa didn't do it consciously. They were almost certainly just  following animals, taking advantage of ecological niches that they could fill, just following their  food and as a result they passively spread across the world. But they may have genuinely made some  more deliberate migrations over in southeast Asia.

[00:12:29]Recently a new hominin has been found on the  island of Luzon in the Philippines and a few years ago stone tools dated to around 700,000 years  ago were also found in the Philippines. What's so special about these discoveries is that the  islands of the Philippines were islands when this was going on. There is no plausible way a hominin  could have walked to these islands. At the very least they would have had a short sea crossing of  a few miles. Though I actually haven't been able to find out exactly how far, but a few miles. So,  the debate is now of course how did these hominins get there? Was it accidental? Were they swept  up in some sort of tsunami or was it deliberate?

[00:13:11]Did they deliberately set out to cross these  few miles of sea and exploit a new territory?

[00:13:31]This is a paleolithic hand axe,  Acheulean handaxe. Not plastic this time.

[00:13:38]The evolution of homo erectus coincides with  the sudden appearance of this new type of tool in the archaeological record. Although it appears  simple this is actually a giant leap forward for humankind. Before this, hominins were producing  Oldowan style tools, and they seemingly when they made those made no effort to shape the core of  the tool. They simply produced a cutting edge and uh that was it. Acheulean tools on the other  hand were flaked on both sides, it was a real revolution and as you can see it required the  removal of a lot of flakes to get it into this nice shape. Even a simple one might remove 20 or  30 flakes, something like that. This really shows a degree of creative thinking on the part of  homo erectus. To be able to take a rock and visualize and understand that through  this process of knapping, through many steps, this handaxe was inside it. It's quite  frankly ingenious, very intelligent indeed, shows an absolutely remarkable degree of of  creative thinking that is unique to our genus.

[00:14:53]Acheulean handaxes probably did not have one  single purpose. They must have been used to hunt, they were certainly used to butcher I'm sure,  and uh perhaps even work wood and bone. They're really the original swiss army knife. These  things are very heavy, you could certainly butcher an animal with this you could certainly  kill something with it no doubt about that.

[00:15:19]How much homo erectus worked with wood and bone is difficult to say. The oldest wooden spears that  have been found so far are the the 500,000 year old or so uh Schoningen spears, which really have  just survived in the archaeological record through a through sheer luck and fluke. They were probably  produced by a Neanderthal or proto-Neanderthal but it is within the same time span as  homo erectus and I personally believe erectus would have been more than capable of of  producing something similar. If you can take 20 or 30 steps to turn a rock into a hand axe for  sure you can sharpen a stick in my opinion.

[00:16:00]As for bone tools again the record  is sparse but it's not incomplete.

[00:16:05]Some of the most distinctive come from Olduvai  Gorge and include this absolutely stunning potential barbed point. Now that is really  incredible. If homo erectus did produce this tool, and evidence suggests they did, then that again  is an absolutely brilliant example of their intelligence. If producing tools and working  with tools is a sign of humanity, is a defining feature of ours, then for sure homo erectus  was uh in the human club no doubt about it.

[00:16:40]oh [_] hell my legs are so stiff. Bloody hell!

[00:16:44]Out of all of the defining features  I've mentioned today, producing art is probably the most defining out of all  of them. No other animal produces art quite like us homo sapiens. So if I'm trying to  decide if if homo erectus was a human or not whether they produced art is key  to that. The best and perhaps only example of creative expression by a homo  erectus hominin is this shell found in java.

[00:17:15]The layer containing the shell was dated to  between 500 and 400,000 years ago roughly.

[00:17:22]So there's absolutely no question it's in the  time span of homo erectus not homo sapiens and as you can see someone has drawn some lines on it,  they've scratched lines into the shell. Do these simple lines count as a creative expression, as  a symbolic act or are they just a careless moment by some ancient hominin? In my opinion it doesn't  matter. It's, it's incredible either way. As with language our artistic expression is also something  that I believe we've learned, that we've evolved to do, and the seeds of all this creativity that  we see around us every single day may have begun with just a simple careless act. A slip of the  hand scratched a shell and maybe that scratch caught the eye of the hominin  that did it and they did another and another and another. In my  personal opinion just these simple acts could have been the spark, could have connected  a couple of neurons in the brain that weren't connected before and and led to absolutely all  the beautiful things we see around us today.

[00:18:31]Not bad if I do say so myself. Eat your heart  out Ettore. There's a new artist in town.

[00:18:43]Everywhere we find erectus we see that it  lived for a really long time. Its fossil record spans almost two million years, from sort  of that two million year mark uh in Ethiopia to 117,000 years ago in Java, Indonesia. So what  caused erectus to meet its ultimate demise? Again, we're not 100% sure but it's likely that the  changing climate played a part. For example, in Indonesia the woodlands were rapidly becoming rain  forest as we know it today and as the conditions became hotter and more humid maybe erectus uh  couldn't adapt to the changing climate there.

[00:19:23]Erectus's legacy has lived on though. As it  traveled the globe it may have left behind populations that eventually evolved into  new species through isolation. One prime candidate is homo floresiensis, found  on the island of Flores in Indonesia.

[00:19:39]The fossils that we found so far date to between  700,000 and 70,000 years ago, which in the scheme of human evolution in prehistory is really  recent. I mean this is the only chapter of human history where we go "70,000 years it's so  recent!" but it's true that is very recent. The adults seemingly were only one meter tall which  has led to them being nicknamed the hobbits.

[00:20:06]Different studies have arrived at different  conclusions, most would probably say that floresiensis descended from erectus and  experienced a phenomenon we call island dwarfism.

[00:20:19]Not everyone agrees though. Others would argue  that they probably derive from an even earlier unknown species just due to some primitive  traits that they have. Maybe some form of australopithecus actually made it out of Africa.  Considering the fact that we know homo erectus was in that region for a very long time they are  the most plausible ancestor but the fact that floresiensis probably suffered from  island dwarfism does suggest that if erectus was able to travel across water,  and I believe they did, they could not do it habitually, they couldn't just choose to  do it any time they wanted. Otherwise they could have just upped and left, they could  have got resources from somewhere else.

[00:21:01]This pressure towards dwarfism  would not have been so pronounced.

[00:21:05]The really weird homo naledi has been proposed  as a potential erectus descendant. I've also made a video on those guys, check it out. Naledi  was found deep in a south African cave in 2013 and so far 15 individuals were recovered  just within one single cave chamber.

[00:21:26]Tres mysterious!

[00:21:27]While we don't know for sure if erectus is their director ancestor it's a solid bet given  the temporal ranges overlapping and the really modern features that naledi has which just  aren't present in early homo or australopiths.

[00:21:43]We are pretty confident though that it gave  rise to at least three species, us neanderthals and denisovans. The identity of the last common  ancestor between us neanderthals and denisovans is still highly debated. We know that an ancestor was  erectus, they're certainly on our family tree but did we descend directly from it? Some, a minority,  but some anthropologists think so. One theory, called the multi-regional hypothesis, argues that  despite the huge geographic distance between homo erectus it could have sort of simultaneously  evolved into homo sapiens across the globe through continuous gene flow. As I said, that is  definitely the minority opinion at the minute.

[00:22:34]Let me add a little bit more information as  to why that is because some of you might be thinking, now that we know that homo sapiens  interbred with neanderthals and denisovans that the multi-regional hypothesis  is therefore correct and, you know, yes and no is basically the answer to that.

[00:22:53]Because of that genetic research we now know that  human evolution took place in multiple regions, Africa, Europe and Asia so in that sense our  evolution is multi-regional. But specifically the multi-regional hypothesis gave no special  place to Africa, but what the fossil record and the genetic evidence suggests is that we  are still predominantly an African species.

[00:23:22]Most of our evolution took place there but it  didn't happen exclusively there. There were very small amounts of absorption you could say of  other archaic hominins. It's just really about the the degree of how much interbreeding happened.  Not that much in the grand scheme of things.

[00:23:41]Others think that there might have been  an intermediate species. The argument is that erectus that stayed in Africa evolved  into a species called homo heidelbergensis, sometime around 800,000 years ago roughly. Homo  heidelbergensis then also migrated out of Africa.

[00:24:00]The ones who stayed in Africa evolved into homo  sapiens and the ones that made it to Europe and Asia evolved into neanderthals and denisovans. The  exact nature of all of the relationships between these various species is not clear and this debate  is famously called the muddle in the middle.

[00:24:19]flalalalala it's taken me  so many takes to say that.

[00:24:22]because it's just so difficult to solve. There  aren't that many fossils that we've found that date to that crucial time period of sort of 800  to 500,000 years ago and each time we do find one, in that very rare event it just complicates  the picture further. It's just difficult to say. It's difficult to talk with any  certainty about complicated events that happened half a million to one million years ago,  naturally that's just a difficult thing to do.

[00:24:56]I'd love to finish this video with an analogy.  Whenever we see chimpanzees or gorillas playing, interacting as a family we can't help but  see ourselves in them. Their mannerisms, their expressions, their games, it's just all  too familiar to us. Now imagine we could travel back in time a million years to some cave  in Indonesia and watch a family of erectuses sitting around a fire, cooking, making tools,  laughing, maybe even talking, we would certainly recognize them as human. Their relationship to us,  their inherent humanity, would be obvious. Despite all the differences between us, despite the huge  amount of time they would be unmistakably human.

[00:25:44]You could say that there's a little erectus in  all of us. Thanks for watching guys, see ya!