What If Humans Didn't Breathe Oxygen?

WHAT IF

11/20/2023

Why do we breathe oxygen and not nitrogen?

Transcript

00:00 One of the first mass extinctions on our planet

00:06 took place long before the dinosaurs.

00:10 Let's go back a couple of billion more years,

00:14 when the Earth's atmosphere

00:15 was completely devoid of oxygen,

00:18 and a clever group of bacteria

00:20 called cyanobacteria got creative.

00:24 They converted sunlight into energy

00:28 and released oxygen as a byproduct.

00:32 To be more specific,

00:33 they became photosynthetic.

00:37 Why was the introduction of oxygen so devastating?

00:41 Why do we humans breathe oxygen

00:43 and not nitrogen?

00:46 And can some animals survive without oxygen?

00:52 This is What If,

00:54 and here's what would happen

00:56 if humans didn't breathe oxygen.

01:01 It was called the Great Oxygenation Event,

01:05 and it began when cyanobacteria

01:07 started turning sunlight into sugar

01:10 and excreting oxygen as waste.

01:13 Yup, photosynthesis.

01:17 But why was this so devastating

01:19 to life on Earth?

01:22 Oxygen began building up in the air and water.

01:27 Millions of anaerobic microorganisms,

01:30 tiny organisms that don't need oxygen to live,

01:33 died when oxygen levels continued

01:36 to increase in the atmosphere.

01:38 This was the beginning of the end

01:40 for a huge portion of life on Earth.

01:44 The gases in our atmosphere

01:47 shape life on Earth.

01:48 78% nitrogen and 21% oxygen

01:53 is the magic proportion.

01:55 So why do we breathe oxygen

01:57 and not nitrogen?

02:00 There are a couple of things

02:01 we need to understand about nitrogen

02:04 before this makes sense.

02:06 Nitrogen tends to bind with nitrogen.

02:10 Think of it as an introvert.

02:11 It rarely interacts with other things.

02:15 It has a covalent triple bond,

02:18 meaning the two nitrogen atoms

02:20 are so tightly bound to each other,

02:22 it takes either a lightning rod

02:24 or certain nitrogen-fixing bacteria

02:26 in the environment to split them apart.

02:30 Compared to nitrogen,

02:32 oxygen is much more like an extrovert,

02:35 and it's very reactive,

02:37 which is why it's used in so many

02:39 biochemical processes that support life.

02:43 But can some animals

02:44 live without oxygen, though?

02:47 Until recently, we believed breathing oxygen

02:50 was essential for all animals to survive.

02:54 But researchers just discovered

02:56 the first animal that doesn't use oxygen

02:59 for breathing, and it's a game changer.

03:02 Hyneguia salmonecola.

03:05 An 8-mm white parasite

03:07 infecting the flesh of Chinook salmon

03:10 has no mitochondrial DNA.

03:12 Yet this is how organisms normally

03:15 use oxygen to produce energy.

03:18 The reason why this animal

03:20 lost its genes to breathe

03:22 is still unclear,

03:24 but it may get its energy

03:26 from its infected host.

03:28 So what would happen if humans

03:31 didn't breathe oxygen?

03:33 How might we have evolved?

03:36 Would we be similar to the salmon parasite,

03:38 relying on a host to survive?

03:41 Or would we live in an underwater

03:44 mythical kingdom like Atlantis

03:46 and never set foot on land?

03:49 Maybe we would become more like plants,

03:51 photosynthesizing sunlight

03:53 to produce needed energy.

03:56 But would we still be considered human

03:59 if this was the case?

04:01 Today, our respiratory system

04:03 is made up of organs that take in oxygen

04:06 and expel carbon dioxide.

04:09 It works in conjunction

04:10 with the circulatory system,

04:12 delivering oxygen-rich blood

04:14 to all the cells in the body.

04:16 The blood then collects CO2

04:19 and other waste to transport

04:20 back to the lungs,

04:21 where it gets pumped out

04:23 when we exhale.

04:25 Without oxygen,

04:26 our current respiratory system

04:28 would either need a complete overhaul

04:30 or would not exist at all.

04:33 The change would be so significant

04:36 that everything in the world

04:37 would be different.

04:39 We likely would not have anything

04:41 in common with this new,

04:42 altered state of being.

04:44 And not having 7.5 billion humans

04:47 emitting CO2 into our atmosphere,

04:50 the process of photosynthesis

04:52 and plant life

04:53 would probably look very different.

04:56 Without the use of oxygen,

04:58 you could even argue

04:59 about our very existence.

05:02 Would we even exist on the planet today?

05:04 If we did,

05:06 we would be like obligate anaerobes,

05:08 organisms intolerant of oxygen.

05:11 This means we wouldn't survive

05:13 unless we lived in a vacuum-like space

05:16 devoid of oxygen.

05:18 So we'd potentially need sealed spacesuits

05:21 to protect us from Earth's atmosphere.

05:25 But what about our appearance?

05:27 Would we have grown

05:28 to the size of humans today?

05:31 We would be much smaller,

05:33 more closely resembling

05:34 the size of those microorganisms,

05:37 needing to stick to larger hosts

05:38 for survival.

05:40 Hopefully, we would fall

05:41 under the facultative anaerobes category.

05:44 They can grow with or without free oxygen,

05:47 so we could easily live

05:48 in the presence of oxygen without harm.

05:52 Fortunately, we have thrived

05:54 because we have evolved

05:55 to rely on oxygen.

05:57 And not just any amount.

05:59 It's the exact right amount of oxygen

06:01 at 21%.

06:04 If there were even a whisper more

06:06 or a gasp less oxygen in our atmosphere,

06:10 we wouldn't be able to live.

06:12 We breathe this oxygen 10 times a minute.

06:16 And if we stopped,

06:17 our brain cells would die off.

06:20 After about 5 minutes without oxygen,

06:23 brain damage happens.

06:25 And if our brain continues

06:27 not to get oxygen,

06:28 it means certain death.

06:32 Everything we see on Earth

06:34 is due to the evolution

06:35 of photosynthesizing bacteria

06:38 that pumped more oxygen

06:39 into the atmosphere.

06:42 Not being able to take advantage

06:44 of this abundance of oxygen

06:46 would have limited us

06:47 from becoming the humans we are today.

06:50 Perhaps instead,

06:52 we would be hanging out

06:53 with our new friends,

06:54 the Heneguya saumonicola parasite,

06:57 all greedily clinging

06:59 to the flesh of Chinook salmon,

07:01 and all living underwater.

07:03 Well, maybe.

07:05 But that's a story for another WHAT IF.

07:10 [music]

What If Humans Didn't Breathe Oxygen?

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