# A world without animals **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 20, 2013, 10:20am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873 "2013-02-20T10:20:21Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Capi1978](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@Capi1978](https://boards.straightdope.com/u/Capi1978)\ **Post date:** [February 20, 2013, 10:20am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/1 "2013-02-20T10:20:21Z")
So how would our earth look like if there weren’t any animals? What vegetation would result? ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [February 20, 2013, 11:06am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/2 "2013-02-20T11:06:30Z")
You mean never developed in the first place, or if all animals were removed now? Because those are two different scenarios. ---
**Author:** ![Capi1978](https://avatars.discourse-cdn.com/v4/letter/c/c5a1d2/32.png) [@Capi1978](https://boards.straightdope.com/u/Capi1978)\ **Post date:** [February 20, 2013, 11:13am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/3 "2013-02-20T11:13:52Z")
Well I`ve originally meant what would happen if we removed all animals now. But the other scenario is interesting, too. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [February 20, 2013, 12:21pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/4 "2013-02-20T12:21:55Z")
Nor really a General Question. Moved to IMHO. **samclem** , moderator ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [February 20, 2013, 12:44pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/5 "2013-02-20T12:44:10Z")
Colder and with sparser vegetation I’d think, with no animals to consume atmospheric oxygen or produce/serve as fertilizer (such as nitrogen fixing). It would probably be a glacial period now I’d think. Plants themselves would be flimsier and don’t produce a lot of the chemicals they do now do to not needing to evolve resistance to being eaten. No flowers, due to there being no insects to attract with them. ---
**Author:** ![leahcim](https://avatars.discourse-cdn.com/v4/letter/l/b4bc9f/32.png) [@leahcim](https://boards.straightdope.com/u/leahcim)\ **Post date:** [February 20, 2013, 1:27pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/6 "2013-02-20T13:27:50Z")
Fewer grasses, since their main advantage over other plants is their tolerance to being “grazed” which will no longer be important. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [February 20, 2013, 2:05pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/7 "2013-02-20T14:05:21Z")
“Animals” - in the sense of mobile multi-cell creatures - would probably evolve from the remaining clades within a few dozen million years anyway. It’s too big a niche to remain empty. ---
**Author:** ![DrFidelius](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drfidelius/32/3447_2.png) [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)\ **Post date:** [February 20, 2013, 2:45pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/8 "2013-02-20T14:45:59Z")
> [@Alessan](#): > > “Animals” - in the sense of mobile multi-cell creatures - would probably evolve from the remaining clades within a few dozen million years anyway. It’s too big a niche to remain empty. My money’s on slime molds. ---
**Author:** ![FrankJBN](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@FrankJBN](https://boards.straightdope.com/u/FrankJBN)\ **Post date:** [February 20, 2013, 3:47pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/9 "2013-02-20T15:47:55Z")
" It would probably be a glacial period now I’d think" Why? Is it your contention that the several ice ages were caused by lack of animal life? ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 21, 2013, 3:27am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/10 "2013-02-21T03:27:51Z")
Isn’t it the case that the world _did_ exist with plants-only, for a long time before any animals began to evolve? In a plants-only world, the plants would consume water and CO[sub]2[/sub] and give off oxygen, without any animals to consume the oxygen, until the atmospheric oxygen reached toxic levels. Then the plants would not be able to be any more prolific, leading to self-limitation of the plant populations (as **Der Trihs** suggests). Or, as suggested in an article in read in _Omni_ circa 1971 or so, the plants would so pollute their environment with oxygen that they would poison themselves. This, however, created exactly that empty niche that **Alessan** mentions above, into which oxygen-consuming critters began to evolve. So, if there weren’t animals, we’d have to invent them. Oh wait… That’s exactly what happened. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [February 21, 2013, 3:42am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/11 "2013-02-21T03:42:24Z")
You might just end up with oxygen consuming plants mixed among the CO2 consumers. If there were never any animals there wouldn’t be flowers to attract insects, and if all the animals disappeared a lot of plants that rely on animals for fertilization would disappear quickly. Plants would probably find more ways of breeding, more mobile seeds, vines that travel disperse pollen maybe. Something would have to break down all the cellulose left from dead plants, so without termites free ranging bacteria would have to do the job. ---
**Author:** ![Timetrvlr](https://avatars.discourse-cdn.com/v4/letter/t/53a042/32.png) [@Timetrvlr](https://boards.straightdope.com/u/Timetrvlr)\ **Post date:** [February 21, 2013, 3:43am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/12 "2013-02-21T03:43:41Z")
A world without animals would be a world without us. A world without us would mean we were not aware of a world at all so it would not exist? I’m getting a brain cramp!😃 ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [February 21, 2013, 3:46am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/13 "2013-02-21T03:46:14Z")
> [@Timetrvlr](#): > > A world without animals would be a world without us. A world without us would mean we were not aware of a world at all so it would not exist? I’m getting a brain cramp!😃 Pretty much what I was going to say. ETA: this religious belief that separates us from the animals is fallacious; we’re all animals of the Earth. Humans happen to be able to communicate and reason: end of story. ---
**Author:** ![Der\_Trihs](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/der_trihs/32/233_2.png) [@Der\_Trihs](https://boards.straightdope.com/u/Der_Trihs)\ **Post date:** [February 21, 2013, 3:49am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/14 "2013-02-21T03:49:01Z")
> [@FrankJBN](#): > > " It would probably be a glacial period now I’d think" > > Why? Is it your contention that the several ice ages were caused by lack of animal life? Plants with no animals to produce carbon dioxide means a weaker greenhouse effect. The [Huronian Ice Age](http://en.wikipedia.org/wiki/Huronian) in fact is believed by many to have been caused by [the oxygenation of the atmosphere](http://en.wikipedia.org/wiki/Great_Oxygenation_Event) by early plant life. ---
**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:** [February 21, 2013, 4:41am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/15 "2013-02-21T04:41:50Z")
> [@Senegoid](#): > > Isn’t it the case that the world _did_ exist with plants-only, for a long time before any animals began to evolve? Depends on what you mean by “plants,” and “animals.” The first cellular organisms were probably bacteria-like. They probably lived off organic compounds that had been formed by inorganic processes. Later some became chemosynthetic. Photosynthesis probably developed much later, in cyanobacteria (blue-green “algae”). So the first organisms ate food they hadn’t produced themselves, like animals. The capability to make food like plants was later. The first eukaryotic organisms (single celled non-bacteria) almost certainly ate bacteria themselves. They gained photosynthetic capability through symbiosis with cyanobacteria. So here too an animal-like lifestyle came first. The first multicellular organisms as well seem to be animal-like rather than plant like. ---
**Author:** ![heathen\_earthling](https://avatars.discourse-cdn.com/v4/letter/h/13edae/32.png) [@heathen\_earthling](https://boards.straightdope.com/u/heathen_earthling)\ **Post date:** [February 21, 2013, 4:52am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/16 "2013-02-21T04:52:06Z")
> [@Timetrvlr](#): > > A world without animals would be a world without us. A world without us would mean we were not aware of a world at all so it would not exist? I’m getting a brain cramp!😃 It existed long before we were here. ---
**Author:** ![the\_apples\_fell](https://avatars.discourse-cdn.com/v4/letter/t/ecb155/32.png) [@the\_apples\_fell](https://boards.straightdope.com/u/the_apples_fell)\ **Post date:** [February 21, 2013, 5:52am UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/17 "2013-02-21T05:52:00Z")
We wouldn’t be here either since we are animals too. ---
**Author:** ![monavis](https://avatars.discourse-cdn.com/v4/letter/m/e0b2c6/32.png) [@monavis](https://boards.straightdope.com/u/monavis)\ **Post date:** [February 21, 2013, 4:41pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/18 "2013-02-21T16:41:15Z")
> [@the\_apples\_fell](#): > > We wouldn’t be here either since we are animals too. Animals existed(and Plants) before there were humans, it seems to me that we need animals and plants more than they need us! ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [February 21, 2013, 4:48pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/19 "2013-02-21T16:48:06Z")
> [@Senegoid](#): > > Isn’t it the case that the world _did_ exist with plants-only, for a long time before any animals began to evolve? > > In a plants-only world, the plants would consume water and CO[sub]2[/sub] and give off oxygen, without any animals to consume the oxygen, until the atmospheric oxygen reached toxic levels. Then the plants would not be able to be any more prolific, leading to self-limitation of the plant populations (as **Der Trihs** suggests). > > Or, as suggested in an article in read in _Omni_ circa 1971 or so, the plants would so pollute their environment with oxygen that they would poison themselves. This, however, created exactly that empty niche that **Alessan** mentions above, into which oxygen-consuming critters began to evolve. > > So, if there weren’t animals, we’d have to invent them. Oh wait… That’s exactly what happened. Are we lumping fungus in with animals here? I tend to think of them as a separate taxonomic kingdom. And if not, to what extent can they pick up the slack from the vanished animals in terms of breaking down organic plant matter and consuming oxygen? ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [February 21, 2013, 10:38pm UTC](https://boards.straightdope.com/t/a-world-without-animals/650873/20 "2013-02-21T22:38:58Z")
Plants are usually thought of as producing oxygen but in fact they need oxygen for [cellular respiration](http://www.ehow.com/about_6513740_cellular-respiration-plants.html) just as animals do; they just happen to produce far more oxygen than they consume (a lot of the glucose they produce is made into cellulose as a building material), thus enabling an oxygen-rich atmosphere.