Did herbivores come first?

[dichotomy]

Did animal life begin as herbivorous?

And if so, does this mean animal classes generally begin as herbivorous before they can have carnivores and omnivores branching off them?

I was thinking about the T-rex nibbling on similar shaped, to itself, herbivores.

[SkepticLance]

This is kind of a 'chicken and the egg' question, and I am sorry to say, a bit meaningless.

 

Long before animals evolved as a separate taxonomic group, there were microorganisms that attacked and killed other life forms. We cannot call them animals, and cannot even call them carnivores, since what they attacked were not animals either. However, the 'life style' was similar to carnivorous. Similarly, some ate photosynthetic microorganisms. We cannot call them herbivores since what they ate were not plants, but were, instead, a kind of microbe plant equivalent.

 

From there, evolution carried the organisms via countless small changes to the point where they could be called animals, and some could be called plants. In between was a grey amorphous region of evolutionary change where the organisms were intermediate to animal, and lived by eating others like themselves or by eating plant equivalents. All kinds of intermediate forms would have existed. Thus, it is not possible to say the first animals were carnivores or herbivores. They were both, or equivalents to both.

[iNow]

Well, simply viewed, plants came before animals, so of course plant eaters came before animal eaters.

[ecoli]

Well, simply viewed, plants came before animals, so of course plant eaters came before animal eaters.

If animals descended from plants, that could be true.

 

But it's not, animals could have just as easily evolved eating each other or non-animal and non-plant organisms as eating plants.

[iNow]

I see your point.

 

Do we have available any evidence of whether or not animals descended from plants? (perhaps its own thread, so as not the completely derail dichotomy's).

[ecoli]

I see your point.

 

Do we have available any evidence of whether or not animals descended from plants? (perhaps its own thread, so as not the completely derail dichotomy's).

http://sci.waikato.ac.nz/evolution/Classification.shtml

 

From what I understand, plant-like cyanobacteria gave rise to plant-like algae and plants themselves. Animals most likely evolved from multicellular protists.

[iNow]

So, then where did multicellular protists come from? Was it not some plant-ish organism?

[SkepticLance]

The exact evolution of the first microorganisms is not known, for the simple reason that these wee beasties did not fossilise. Bacteria-like organisms and Archean-like organisms probably were early examples. These were neither plants nor animals. They would have evolved into Eucaryotes which were still microscopic, and which still left no fossil trace. The first such Eucaryotes would also have been neither plant nor animal.

 

Life began 3 to 4 billion years ago, and remained unsuited to forming clear cut fossils till 1 billion years ago. Whether anything like plants and animals evolved before this time will remain speculative. The first true plants and animals probably evolved separately. It is not possible to say if the first animals ate plants. They might have been a kind of filter feeder that ate bacteria. Who knows?

[iNow]

Thanks, Lance. You raise a good point. I suppose part of the issue with our terms "herbivore" and "carnivore" is that they don't really extend well into micropaleobiology. They apply well in macroscopic and recent contexts, but have limited applicability after that.

 

Basically, if a bacteria-like organism eats another bacteria-like organism, is that being a carnivore or an herbavore?

If a bacterial-like organism eats an archean-like organism, is that being a carnivore or an herbivore?

If an archean-like organism eats another archean-like organism eats another archean-like organism, is that being a carnivore or an herbivore.

 

 

It would appear that the distiction is quite meaningless at that level, and can only be applied to larger (I'm thinking mammalian here, but know others are included) organisms.

[falcon9393]

ehh i think herbivors deffinitly came first.. and then one of them went cannible and evolved and thats how we got carnivors its not right though and it sounds stupid when i say it so ya oh an i know my spelling sucks!

[lucaspa]

Well, simply viewed, plants came before animals, so of course plant eaters came before animal eaters.

 

In terms of land organisms, yes. Plants evolved to live on land earlier than animals. But it is not clear whether the first amphibians were herbivores or carnivores. Once on land, the first species of amphibians is rapidly going to radiate to take advantage of the empty ecological niche of herbivore. Then there is going to be nearly simultaneous radiation from the ancestral species to prey on the other amphibians.

 

But to answer the the OP, we have 4 classes within vertebrates: amphibians, reptiles, birds, and mammals. As I recall, the first dinos were insectivores/carnivores -- eating insects and small reptiles and mammal-like reptiles. So, in that case, the carnivore came first.

 

Birds evolved from carnivorous theropod dinosaurs and the first birds were carnivorous.

 

So, then where did multicellular protists come from? Was it not some plant-ish organism?

 

It's not definitive. Bacteria today cooperate at times such that they are almost multicellular. The amoeba Dictolystelium is single celled sometimes and multicelled at other times. It is not "plant-ish" in that it does not photosynthesize.

 

The simplest multicellular creature now is the Volvox, which is a hollow sphere of a single type of somatic cells and then has germ cells: so it has only 2 types of cells. As I recall, Volvox feeds on unicellular organisms.

[dichotomy]

But to answer the the OP, we have 4 classes within vertebrates: amphibians, reptiles, birds, and mammals.

 

And Fish? But I think you might be referring to land creatures?

 

Ok, so in terms of land animals herbivores came first. With amphibians it is unknown, and early life probably fed on itself, a form of cannibalism perhaps?

 

What this is sort of telling me, I think, is that unconscious life doesn't think in terms of animal, mineral or vegetable, it thinks in terms of what available nutrients can I use. Very logical really.

[iNow]

What this is sort of telling me, I think, is that unconscious life doesn't think in terms of animal, mineral or vegetable, it thinks in terms of what available nutrients can I use.

I think that's a nice way of looking at it. It seems valid, and you might even expand it by changing the word "nutrients" to "resources."

[dichotomy]

I think that's a nice way of looking at it. It seems valid, and you might even expand it by changing the word "nutrients" to "resources."

 

Why’s that? To include stalactites?

[SkepticLance]

To dichotomy

 

Your sarcasm does you little credit. Some organisms can use, as resources, such diverse materials as sulfur, or hydrogen gas, or methane or any source of energy. Stalactites are not likely to be used as a resource since they are low in chemical energy.

[lucaspa]

And Fish? But I think you might be referring to land creatures?

 

I simply forgot to include fish.

 

Ok, so in terms of land animals herbivores came first. With amphibians it is unknown, and early life probably fed on itself, a form of cannibalism perhaps?

 

It's not clear what came first in land animals. Plants were on the land before the first amphibians. We don't know whether the first amphibians were carnivores or herbivores. Acanthostega was one of the first tetrapods and a probable ancestor to amphibians. The pictures show teeth consistent with being a carnivore: http://tolweb.org/Acanthostega

 

But that doesn't mean the first amphibians were cannibals. They could have eaten fish. Or insects. AFter all, they are only on land part of the time; so they could have hunted fish. Or eaten the insects that were already on the land.

 

What this is sort of telling me, I think, is that unconscious life doesn't think in terms of animal, mineral or vegetable, it thinks in terms of what available nutrients can I use. Very logical really.

 

Evolution doesn't think, period. You are trying to apply volition (decision) to evolution. That isn't how evolution works. An individual is either lucky or unlucky in the alleles (forms of genes) it is born with. If those alleles let it exploit a new food source -- such as plants for a carnivore or animals for a herbivore -- then that lucky individual will do better in the struggle for scarce resources. In this case the scarce resource would be food and the lucky individual would have a food source the others did not. So the lucky individual lives better and has more offspring -- many of whom will inherit the alleles to exploit the new food source. After hundreds of generations (with more lucky individuals having alleles that can exploit the new food source better), you will have a population that is now exploiting the new food source.

 

I explained this all in detail because you used an incorrect shorthand. Evolutionary biologists often speak of "amphibians evolved the ability to walk on land" as tho it were a choice of the individuals involved. It's convenient shorthand. But you seem to have believed the shorthand as the reality.

 

I think that's a nice way of looking at it. It seems valid,

 

It's not a good way to look at it and it's not valid. It's a misrepresentation of what happens in evolution. Dichotomy really seems to think that organisms "think in terms of resources" and then choose to exploit what is handy! That injects consciousness into evolution and natural selection. In this case, consciousness of the individuals who somehow "choose" to be able to eat plants when they are a carnivore or vice versa.

 

And, yes, Dichotomy, "resources" is often food, but it can be licking stalactites to get needed minerals. Or it can be using a forest to stay hidden from a predator. Or, in the case of mudskippers today, using the land as a resource to escape predators (mudskippers can use their front fins and primitive legs and can breathe out of water).

[iNow]

I suggest that dichotomy may have just been using "convenient shorthand," and was not suggesting this was the reality of evolution.

 

I could be wrong, though. I was simply offering an observation, an opinion actually, that I thought it was a nice way of looking at things.

[bascule]

I was under the impression the common ancestor of all animals was a filter-feeding sponge-like organism which evolved the first nerve cells in order to pick a location to attach itself to, after which it "digested its brain"

[SkepticLance]

We simply do not know what the first animal was. In Precambrian rocks, there is a vast lack of fossils. Just a few idiocarans and various mudstone impressions.

 

Even the phrase 'first animal' is of limited meaning. The first organism with enough of the appropriate animal traits was likely to be very similar to the last one with insufficient. In fact, the distinction would be highly subjective. Even if we had fossils of every generation of these organisms, it would be almost impossible to know where to draw the line and say : "This organism was the first animal. That other organism was not an animal."

 

If we made a subjective judgement based on this non existent fossil record, and pointed to one species as the first animal, it might have eaten almost anything, as far as we can know. Carnivore, herbivore, filter feeder, or even obtaining nutrients by being in symbiotic union with bacteria or single celled algae.

 

Lucaspa, I think, has misunderstood the question, and talked about vertebrates. The question was not vertebrates, but animals - quite different as Lucaspa well knows.

[dichotomy]

To dichotomy

 

Your sarcasm does you little credit. Some organisms can use, as resources, such diverse materials as sulfur, or hydrogen gas, or methane or any source of energy. Stalactites are not likely to be used as a resource since they are low in chemical energy.

 

Your translation does you little credit. No sarcasm was intended at all, I was stating, in a fun way, that stalactites might be included as a kind of animal or proto animal, that didn’t need nutrients as such, but did need resources to grow. Again, I’m not being serious here, just being human.

If anything I was asking what animals there are that didn’t need nutrients (as I was talking about food and water in this thread). As iNow’s ‘resources’ seemed to imply there are nutrients, outside of food and water, to sustain life. But again, I could be interpreting iNow incorrectly, and he me. Sheesh this is hard work…

 

I suggest that dichotomy may have just been using "convenient shorthand' date='" and was not suggesting this was the reality of evolution. [/quote']

 

Exactly. Assumptions are rampant in humanity, but I accept this.

And of the statement, "amphibians evolved the ability to walk on land"; I wouldn’t interpret this as an animal making a conscious choice to adapt…Honest!

 

Hey look, that poodle is riding a bicycle, must have been a conscious choice to adapt.

 

Also, thanks Lucaspa, I do appreciate the reliable information you deliver. I know my humour and convienient shorthand can be a little confusing at times. It's a time issue really.

[SkepticLance]

To dichotomy

 

My apologies for misinterpreting your comment.

 

The word 'nutrient' is a tricky one. It can include all sorts of materials, including vitamins, minerals, antioxidants, etc. I think, for the purposes of this discussion, it is better to consider energy sources, than all ancillary nutrients. This tends to be the main thrust in ecology, and the search for energy, more than other nutrients, is a major driver in evolution.

 

Various organisms can obtain energy from a range of sources. I am fascinated by the 'worms' found next to black smokers - deep ocean volcanic vents. In the darkness, immense pressure and extreme high temperatures there, they have found a source of energy utilised with symbiotic bacteria. They hold bacteria inside their bodies, which convert the inorganic chemicals from the volcanic vent into energy. The bacteria die at a rapid rate, and are replaced by new bacteria. The dead bacteria become food for the 'worms'. The energy source here is not organic chemicals as we expect from carnivores and herbivores, or sunlight, as we expect with green plants - but sulfates, which are totally inorganic and the result of geological processes.

 

The ultimate source for that energy is probably nuclear fission. Ancient Uranium, left over from the formation of the solar system, splits to release heat, which in turn drives the chemical reactions in the magma to make the sulfates, and thus give energy to living organisms.

[dichotomy]

To dichotomy

 

My apologies for misinterpreting your comment.

 

No problem. Lost in translation.

 

The word 'nutrient' is a tricky one. It can include all sorts of materials, including vitamins, minerals, antioxidants, etc. I think, for the purposes of this discussion, it is better to consider energy sources, than all ancillary nutrients. This tends to be the main thrust in ecology, and the search for energy, more than other nutrients, is a major driver in evolution.

 

Yes, energy sources makes more sense at this point in the discussion. Originally I was thinking of vertebrates (carnivoresm & herbivores), but it's been much more interesting to leave it open. Shows me just how complex it is to classify things.

[bascule]

We simply do not know what the first animal was. In Precambrian rocks, there is a vast lack of fossils. Just a few idiocarans and various mudstone impressions.

 

Richard Dawkins at least speculates in the Ancestor's Tale that modern animals descended from Placozoans, particularly of the Trichoplax genus, which are descended from sponges.

 

Even the phrase 'first animal' is of limited meaning. The first organism with enough of the appropriate animal traits was likely to be very similar to the last one with insufficient. In fact, the distinction would be highly subjective

 

I think the development of neurons is the seminal animal trait, and it's a development which occurred in sponges.

[lucaspa]

We simply do not know what the first animal was. In Precambrian rocks, there is a vast lack of fossils. Just a few idiocarans and various mudstone impressions.

 

Add to that the problem that most bacteria and archaens do niot photosynthesize. Are they animals?

 

Lucaspa, I think, has misunderstood the question, and talked about vertebrates. The question was not vertebrates, but animals - quite different as Lucaspa well knows.

 

The OP says "And if so, does this mean animal classes generally begin as herbivorous before they can have carnivores and omnivores branching off them? "

 

So the question wasn't about the first division of animals from plants, but about all subsequent evolutionary branching of the Kingdom Animalia. It appears that you missed that.

 

Richard Dawkins at least speculates in the Ancestor's Tale that modern animals descended from Placozoans, particularly of the Trichoplax genus, which are descended from sponges.

 

Dawkins speculations have a very low percentage of success.

 

I think the development of neurons is the seminal animal trait, and it's a development which occurred in sponges.

 

http://neurophilosophy.wordpress.com/2007/06/09/sea-sponges-have-the-makings-of-a-nervous-system/

"Sea sponges are sedentary organisms that attach themselves to the sea bed and filter nutrients from the water that they force through their porous bodies with flagella. They are the most primitive of all multicellular animals, with just four different types of cells making up partially differentiated tissues in a simply organized body. Because of the lifestyle they lead, sea sponges do not need, and therefore lack, nerve cells, muscle cells and internal organs of any kind. However, researchers from the University of California at Santa Barbara now find that one species of sea sponge, called Amphimedon queenslandica, synthesizes many of the proteins that are essential for the cell-to-cell communication that takes place within nervous systems. These surprising findings, which are published in the open access journal PLoS One, therefore provide clues about how the first neurons may have evolved in the most ancient of animals."

 

That evolution of neurons doesn't appear to have been in sponges but come in a later lineage.

 

And of the statement, "amphibians evolved the ability to walk on land"; I wouldn’t interpret this as an animal making a conscious choice to adapt…Honest!

 

I'm glad about that. But that wasn't what I was reacting to. It was your statement "What this is sort of telling me, I think, is that unconscious life doesn't think in terms of animal, mineral or vegetable, it thinks in terms of what available nutrients can I use."

 

It was the use of the word "thinks" that prompted my response. That "think" does mean a conscious choice, doesn't it?

 

If you want to avoid the confusion in the future, do not use the word "think" when talking about evolution; there is no "thinking" involved on the part of organisms.

[Skye]

Cnidaria are the most primitive animals with neurons, as far as I know.

 

Sponges are the most primitive animals around now. How they emerged isn't completely clear, as they have different cells types that line up with different protists. The most obvious in that choanocytes match up very well with choanoflagellates, and this has been the most likely origin for a long time. But it isn't set in stone.

 

As far as carnivore/herbivore goes, in ecology these are sometimes combined into predation. But that still leaves things like parasitism and detritivores out.