Fire, like life, is only known to exist on Earth.

And humans are the only species that has fully figured out how to harness all that firepower. Even though some species need fire  to create their favorite habitat or to accomplish an important  part of their life cycle, they’re not, like, making it themselves.

Fire is an experts only gadget,  and we are those experts. Learning to get along with  fire, benefiting from it, harnessing it, took some time. Like they say: you play with  fire, you're gonna get burned.

And no doubt we did. Lots of us. Repeatedly.

Over the course of many thousands of years. It is still happening today… Eventually, fire became our thing. But exactly when that happened is way more of a mystery than you might think. [♪ INTRO] To start off, let’s get a little  background on fire itself.

The chemical reaction to make  fire has only been possible here on Earth since this planet  got its oxygen atmosphere. The earliest geologic evidence  of wildfires is from about 430 million years ago, when  atmospheric oxygen levels reached the 16% necessary to sustain a blaze. And obviously, that’s way, way before any of us sentient apes were around, meaning that all the fires that  happened for hundreds of millions of years were due to things like  lightning strikes and volcanoes.

None of the OG fire users  left us any diary entries, so when and how we figured out how to harness it is a surprisingly controversial question. It's generally agreed that our  ancestors started tinkering with fire in Africa, since that’s also where  our whole lineage first evolved. And wildfires were pretty  infrequent in Africa until between 7 and 8 million years ago  when the tropical rainforests began to dry out, and got replaced by grasslands – an ecosystem in which high intensity fires thrive.

That’s around the same time  and place that hominins began to emerge, which a lot of  experts think is no coincidence. Fire-swept landscapes might  have been appealing to our ancestors because predators  didn't like to hang out there. But as the old maxim says, come  for the absence of jaguars, stay for the burnt rodent carcasses!

Wait, has no one else heard that one before? And yeah, it's been argued  that our species is defined by our connection to fire early in our evolution. At some point, being able to eat food cooked instead of raw boosted our nutrition, which was great for our  ancestors' brain development.

In addition to growing big noggins  by enjoying superior snacks, fire gave us protection, warmth, and a focal point for social gatherings and a forge to make tools. So, it's one thing to casually benefit  from a fire-dependent landscape, but how exactly did a bunch of primates learn to harness a grassland wildfire that was 380°C? At first, they probably didn't.

Our ancestors’ first use of  fire was likely opportunistic: they’d just take advantage of whatever got left behind after a naturally  occurring wildfire swept through. Smokey fires were easy to spot and  follow around in the landscape, and they made good places to  ambush prey, not to mention the protection they offered from  predators and biting insects. Hominins could have even fed these  fires by adding their own fuel, like more unburned brush  or slow-burning animal poo.

Which I bet smelled awesome. But the big question is when we started kindling, sustaining and spreading fire around. Anthropologists and archaeologists  still aren’t sure they’ve found the oldest evidence of human-controlled  fire that might be out there.

So, what evidence do we need to figure out when early humans became fire experts? To answer this question, researchers  first look for the same stuff that signals the presence of  Earth's very first fires: charcoal. But since the charcoal residue from a wildfire and a controlled fire look the  same, you need more than that.

Hence, the controversy over when we became proficient with the hot stuff. In general, charcoal needs to show up along with some other evidence in  order for experts to agree. One sign that the folks knew what they were doing with fire is the presence of a hearth – a ring of stone with charcoal  that’s only found inside the ring, as opposed to scattered around the settlement.

That shows that a fire was tightly contained, and implies it was fully under somebody’s control. Extra points for evidence of earth that was baked at high temperatures, not just charcoal alone. Baked earth would indicate that a fire burned in one spot for a long time,  and in order to keep that going, somebody would need to add more fuel.

The site also needs to look like  it was inhabited by hominins, so a cave strewn with bones  and tools is an ideal example. Another way to tell whether fire was used intentionally is the presence  of heat-treated rock. Turns out that treating  your rocks with fire or heat before whacking them into stone  tools made the source material easier to fashion into things  like axes and spearheads.

But evidence of cooking in a settlement is a pretty ironclad signal that some people were able to use fire in a controlled  way as a part of daily life. Cooking sites are hard to  dispute, because they often check all the boxes archaeologists need to agree that these people were fire professionals. Some archaeological sites dating back at least one million years have some of  these characteristics, but not all.

Which is where the controversy comes in – it's possible these scorched bits of earth were just the products of wildfires that were neither created nor controlled by humans. Many researchers think that Homo erectus may have been cooking with fire as  far back as 1.7 million years ago, based on evidence of them making hearths. However, the evidence is sporadic, indicating that they weren’t  really doing this all the time.

Counter arguments say ​​that sure, fire might have been used occasionally  for a million or so years, but our ancestors weren't barbecue pit masters until a few hundred thousand years ago. But how many hundred thousand years ago? The oldest site showing pretty  irrefutable controlled use of fire is Gesher Benot Ya‘aqov in Israel,  a 780,000-year-old settlement on the banks of ancient Lake Hula.

No hominin remains have been found there, but there are lots of fish bones, stone tools, burnt seeds, wood and flint,  and evidence of cooking. It’s clear that multiple fires  were lit on the same spot, over an extended period of occupation. Other sites like Tabun Cave  in Israel show this at around 380,000 years, which really seals  the deal on humans using fire.

But regardless of exactly when it happened, we do know that once humans  figured out how to use fire, the hot stuff, there was no looking back. We shape landscapes with it, we cook all our favorite foods with it, and we even invented the  internal combustion engine and began burning old fossilized plants, too. Human time here on this planet  has been made possible by fire– this neat little trick only Earth can play.

And if what I said earlier about  fires only being possible on Earth for a few hundred million years  piqued your interest, you’re in luck! Our friends at Eons made a  whole video about just that. Go check it out, and all of their other great paleontology and evolutionary videos, too.

Thanks for watching! [♪ OUTRO]