# When's the earliest a human could survive on Earth? **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2013, 4:03pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851 "2013-11-01T16:03:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Mr.Kobayashi](https://avatars.discourse-cdn.com/v4/letter/m/4af34b/32.png) [@Mr.Kobayashi](https://boards.straightdope.com/u/Mr.Kobayashi)\ **Post date:** [November 1, 2013, 4:03pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/1 "2013-11-01T16:03:16Z")
As you all know I’m a time traveller; this time I want to travel back as far back as it is possible to go and still remain on Earth. This rock is about 4.5 billion years old, but its teething age was apparently [none too pleasant](http://en.wikipedia.org/wiki/Hadean). I’d like to be able to, y’know, breath and shit. When’s the earliest I could travel back to and not die? For bonus points, when could I get something to eat and drink that wouldn’t kill me? ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [November 1, 2013, 4:40pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/2 "2013-11-01T16:40:04Z")
Unless you took along a whole integrated community with you, you wouldn’t even be able to survive today, completely on your own. Humans did not evolve to survive as solitary individuals, and there are few examples of humans who survived for decades completely isolated from any other humans or any man-made conveniences. I understand the meaning of your question, but the problem is that a human time traveler would not have anywhere near the success expectations of a non-social mammal, in any era or environment. It might be more relevant to ask how early a mammal could survive on earth. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 1, 2013, 4:54pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/3 "2013-11-01T16:54:14Z")
There wouldn’t have been enough oxygen for you to breath until the [Great Oxygenation Event](http://en.wikipedia.org/wiki/Oxygen_catastrophe) about 2.4 billion years ago. There would have been subsequent times when survival would have been nearly impossible, in particular during [Snowball Earth](http://en.wikipedia.org/wiki/Snowball_Earth) periods. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [November 1, 2013, 4:56pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/4 "2013-11-01T16:56:56Z")
Prior to about two and a half billion years ago, there wasn’t enough oxygen in the atmosphere to sustain human life. Then there was the “great oxygenation event”, where O2 levels rose dramatically. The earth’s atmosphere was still pretty wonky though, and probably not too breathable for humans. And then you’ve got all kinds of glaciation events and stuff to make things even more fun. You don’t really get stable O2 in the air until the last billion years or so. I would say you would probably want to get past the last snowball earth period (because being deep frozen wouldn’t be too pleasant either), which puts you up at about the last 650 million years or so. On previous I see that Colibri ninja’s me. I guess I need to learn how to type faster. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [November 1, 2013, 5:03pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/5 "2013-11-01T17:03:37Z")
See chart here: [http://www.nap.edu/openbook/0309100615/gifmid/30.gif](http://www.nap.edu/openbook/0309100615/gifmid/30.gif) Pretty much any time after the Cambrian, you wouldn’t die.There are many periods when the O2 concentration drops below the OSHA required minimums of 19.5%, in which case you will probably feel the lack of oxygen (and your employer would receive a fine), but there likely won’t be any dire health effects until you get below 15% or so. There are probably also periods in the late Precambrian where you would be able to survive, but none when you’d be in OSHA compliance. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [November 1, 2013, 5:21pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/6 "2013-11-01T17:21:19Z")
> [@GreasyJack](#): > > See chart here: [http://www.nap.edu/openbook/0309100615/gifmid/30.gif](http://www.nap.edu/openbook/0309100615/gifmid/30.gif) > > Pretty much any time after the Cambrian, you wouldn’t die.There are many periods when the O2 concentration drops below the OSHA required minimums of 19.5%, in which case you will probably feel the lack of oxygen (and your employer would receive a fine), but there likely won’t be any dire health effects until you get below 15% or so. There are probably also periods in the late Precambrian where you would be able to survive, but none when you’d be in OSHA compliance. I’d also worry about the CO2 concentrations. Our present atmosphere is around 0.04 % CO2. High levels cannot be tolerated. Wiki sez: > [@](#): > > Adaptation to increased levels of CO2 occurs in humans. Continuous inhalation of CO2 can be tolerated at three percent inspired concentrations for at least one month and four percent inspired concentrations for over a week. It was suggested that 2.0 percent inspired concentrations could be used for closed air spaces (e.g. a submarine) since the adaptation is physiological and reversible. Decrement in performance or in normal physical activity does not happen at this level.[84][85] However, it should be noted that submarines have carbon dioxide scrubbers which reduce a significant amount of the CO2 present.[86] Levels over 7% present danger of suffocation. ---
**Author:** ![Cartoonacy](https://avatars.discourse-cdn.com/v4/letter/c/848f3c/32.png) [@Cartoonacy](https://boards.straightdope.com/u/Cartoonacy)\ **Post date:** [November 1, 2013, 5:29pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/7 "2013-11-01T17:29:20Z")
> [@jtur88](#): > > Unless you took along a whole integrated community with you, you wouldn’t even be able to survive today, completely on your own. Humans did not evolve to survive as solitary individuals, and there are few examples of humans who survived for decades completely isolated from any other humans or any man-made conveniences. I don’t think the OP is talking about surviving for decades. It sounds to me like what he has in mind is more along the lines of a weekend camping trip. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [November 1, 2013, 5:30pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/8 "2013-11-01T17:30:59Z")
OTOH, forget that as a warning concerning immediate danger. I was misplacing a decimal point and using 0.4% instead of 0.04% when thinking about it. The Cambrian is about 18 to 25 times today’s concentration of CO2 - probably OK, though you might want to worry about prolonged effects. ---
**Author:** ![bup](https://avatars.discourse-cdn.com/v4/letter/b/6bbea6/32.png) [@bup](https://boards.straightdope.com/u/bup)\ **Post date:** [November 1, 2013, 5:47pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/9 "2013-11-01T17:47:39Z")
> [@GreasyJack](#): > > Pretty much any time after the Cambrian, you wouldn’t die. That’s also my answer for when you’d be able to feed yourself. In shallow seas, you’d be able to find mollusks to cook up, and you could get really clean rain water - probably by following a seashore, you’d eventually find a freshwater feeder stream. ---
**Author:** ![Habeed](https://avatars.discourse-cdn.com/v4/letter/h/a587f6/32.png) [@Habeed](https://boards.straightdope.com/u/Habeed)\ **Post date:** [November 1, 2013, 5:52pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/10 "2013-11-01T17:52:04Z")
Don’t forget hostile micro-organisms. Sure, theoretically, your immune system is “more evolved”, but that is not really how evolution works. There could have been pathogens ten million years ago that had some novel and highly effective method for attacking you, that lost this ability due to it being too effective or genetic drift or whatever. Since you’re a time traveler, why don’t you copy down some stock market performance data and hop a few years into the past. Earn yourself enough money trading stocks based on your fore-knowledge to have someone custom-build the kind of survival equipment you’d need. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [November 1, 2013, 6:09pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/11 "2013-11-01T18:09:58Z")
Need answer fast? Oh, of course not. You’re a time traveler. ---
**Author:** ![bup](https://avatars.discourse-cdn.com/v4/letter/b/6bbea6/32.png) [@bup](https://boards.straightdope.com/u/bup)\ **Post date:** [November 1, 2013, 6:18pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/12 "2013-11-01T18:18:26Z")
> [@Habeed](#): > > Don’t forget hostile micro-organisms. Yes, I made an assumption that you could bring camping equipment, including a gas stove to boil all water and cook all critters. That was not explicit in the op, though, and maybe I shouldn’t have. Depending on where you were in the Cambrian, you could eat snow for water, and dry out plants for food. That would probably be pretty safe. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [November 1, 2013, 6:22pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/13 "2013-11-01T18:22:00Z")
> [@Habeed](#): > > Don’t forget hostile micro-organisms. Sure, theoretically, your immune system is “more evolved”, but that is not really how evolution works. There could have been pathogens ten million years ago that had some novel and highly effective method for attacking you, that lost this ability due to it being too effective or genetic drift or whatever. On the other hand, there would be no pathogens evolved to exploit humans (or even mammals, if you go back far enough.) Many human pathogens evolved from those in birds and pigs living in close association with humans (mostly in Asia, after the advent of agriculture, one of the main reasons why American aborigines were susceptible.) One wonders which factor is more significant, lack of offense or lack of defense. I suspect we’d be far safer from viruses, but we might be more prone to bacterial infections. Please do provide us with the results of your immunological experiment! ---
**Author:** ![Mr.Kobayashi](https://avatars.discourse-cdn.com/v4/letter/m/4af34b/32.png) [@Mr.Kobayashi](https://boards.straightdope.com/u/Mr.Kobayashi)\ **Post date:** [November 1, 2013, 7:24pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/14 "2013-11-01T19:24:14Z")
> [@jtur88](#): > > Unless you took along a whole integrated community with you, you wouldn’t even be able to survive today, completely on your own. Humans did not evolve to survive as solitary individuals, and there are few examples of humans who survived for decades completely isolated from any other humans or any man-made conveniences. Fear not, in the 23rd century I assimilated the survival knowledge of a Ray Mears hologram. > [@GreasyJack](#): > > See chart here: [http://www.nap.edu/openbook/0309100615/gifmid/30.gif](http://www.nap.edu/openbook/0309100615/gifmid/30.gif) > > Pretty much any time after the Cambrian, you wouldn’t die.There are many periods when the O2 concentration drops below the OSHA required minimums of 19.5%, in which case you will probably feel the lack of oxygen (and your employer would receive a fine), but there likely won’t be any dire health effects until you get below 15% or so. There are probably also periods in the late Precambrian where you would be able to survive, but none when you’d be in OSHA compliance. Fascinating! I had no idea the oxygen fluctuated that much. > [@Learjeff](#): > > On the other hand, there would be no pathogens evolved to exploit humans (or even mammals, if you go back far enough.) Many human pathogens evolved from those in birds and pigs living in close association with humans (mostly in Asia, after the advent of agriculture, one of the main reasons why American aborigines were susceptible.) > > One wonders which factor is more significant, lack of offense or lack of defense. I suspect we’d be far safer from viruses, but we might be more prone to bacterial infections. > > Please do provide us with the results of your immunological experiment! I have a mild case of proto-syphilis. Don’t ask me how. ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [November 1, 2013, 8:10pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/15 "2013-11-01T20:10:39Z")
> [@Mr.Kobayashi](#): > > I have a mild case of proto-syphilis. Don’t ask me how. Shouldn’t shag with the Cro-Magnons, [no matter how hot](http://www.talltalestruetales.com/wp-content/uploads/2009/04/clan-of-the-cave-bear_l1.jpg). ---
**Author:** ![Blue\_Blistering\_Barnacle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blue_blistering_barnacle/32/3386_2.png) [@Blue\_Blistering\_Barnacle](https://boards.straightdope.com/u/Blue_Blistering_Barnacle)\ **Post date:** [November 1, 2013, 9:15pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/16 "2013-11-01T21:15:22Z")
> [@bup](#): > > Yes, I made an assumption that you could bring camping equipment, including a gas stove to boil all water and cook all critters. That was not explicit in the op, though, and maybe I shouldn’t have. > > Depending on where you were in the Cambrian, you could eat snow for water, and dry out plants for food. That would probably be pretty safe. Maybe algae or seaweed or possibly lichen, but not an apple tree (or any other dryland plant) in sight. ---
**Author:** ![James\_Toothpaste](https://avatars.discourse-cdn.com/v4/letter/j/e56c9b/32.png) [@James\_Toothpaste](https://boards.straightdope.com/u/James_Toothpaste)\ **Post date:** [November 1, 2013, 9:51pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/17 "2013-11-01T21:51:05Z")
The Cambrian or later. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [November 1, 2013, 10:25pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/18 "2013-11-01T22:25:27Z")
> [@bup](#): > > That’s also my answer for when you’d be able to feed yourself. In shallow seas, you’d be able to find mollusks to cook up, and you could get really clean rain water - probably by following a seashore, you’d eventually find a freshwater feeder stream. You might be able to find food much earlier than that by eating cyanobacteria (blue-green algae) such as [_Spirulina_](http://en.wikipedia.org/wiki/Spirulina_(dietary_supplement)). Cyanobacteria potentially produce most needed nutrients including vitamins, but it might be difficult getting an appropriate balance. ---
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [November 1, 2013, 11:11pm UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/19 "2013-11-01T23:11:48Z")
Are you allowed to bring back modern plants, animals, fungi, or other life forms? If so, which ones do you think would be best in terms of surviving and providing a benefit for humans back then? Would wheat grow in the early Cambrian period, or would there not be adequate soil for that? Bring back barley, hops, and yeast and start your own 10 Million BC Brewery. Tell us where you’ll be hiding your surplus so we can go pick it up next week. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [November 2, 2013, 12:16am UTC](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851/20 "2013-11-02T00:16:20Z")
> [@jtur88](#): > > Unless you took along a whole integrated community with you, you wouldn’t even be able to survive today, completely on your own. You’re fighting the hypothetical. A Time traveler presumably can depart at will, and thus need not suffer from being alone. Provided air, food, water and a tolerable climate are available (and no hostile critters are around) a stay of weeks to months could be quite pleasant. [Next page](https://boards.straightdope.com/t/whens-the-earliest-a-human-could-survive-on-earth/672851.md?page=2)