Theory on origin of animals challenged: Earliest animal life may have required little oxygen

Feb 17, 2014
Sea sponge Halichondria panicea was used in the experiment at the University of Southern Denmark. Credit: Daniel Mills/SDU

One of science's strongest dogmas is that complex life on Earth could only evolve when oxygen levels in the atmosphere rose to close to modern levels. But now studies of a small sea sponge fished out of a Danish fjord shows that complex life does not need high levels of oxygen in order to live and grow.

The origin of complex life is one of science's greatest mysteries. How could the first small primitive cells evolve into the diversity of advanced life forms that exists on Earth today? The explanation in all textbooks is: Oxygen. Complex life evolved because the atmospheric levels of oxygen began to rise app. 630 – 635 million years ago.

However new studies of a common from Kerteminde Fjord in Denmark shows that this explanation needs to be reconsidered. The sponge studies show that animals can live and grow even with very limited oxygen supplies.

In fact animals can live and grow when the atmosphere contains only 0.5 per cent of the oxygen levels in today's atmosphere.

"Our studies suggest that the origin of animals was not prevented by low oxygen levels", says Daniel Mills, PhD at the Nordic Center for Earth Evolution at the University of Southern Denmark.

Together with Lewis M. Ward from the California Institute of Technology he is the lead author of a research paper about the work in the journal PNAS.

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A little over half a billion years ago, the first forms of complex life - animals - evolved on Earth. Billions of years before that life had only consisted of simple single-celled life forms. The emergence of animals coincided with a significant rise in , and therefore it seemed obvious to link the two events and conclude that the increased oxygen levels had led to the evolution of animals.

"But nobody has ever tested how much oxygen animals need – at least not to my knowledge. Therefore we decided to find out", says Daniel Mills.

The living animals that most closely resemble the first animals on Earth are sea sponges. The species Halichondria panicea lives only a few meters from the University of Southern Denmark's Marine Biological Research Centre in Kerteminde, and it was here that Daniel Mills fished out individuals for his research.

"When we placed the sponges in our lab, they continued to breathe and grow even when the oxygen levels reached 0.5 per cent of present day atmospheric levels", says Daniel Mills.

Sea sponge Halichondria panicea was used in the experiment at University of Southern Denmark. Credit: Daniel Mills/SDU

This is lower than the oxygen levels we thought were necessary for animal life.

The big question now is: If low oxygen levels did not prevent animals from evolving – then what did? Why did life consist of only primitive single-celled bacteria and amoebae for billions of years before everything suddenly exploded and complex life arose?

"There must have been other ecological and evolutionary mechanisms at play. Maybe life remained microbial for so long because it took a while to develop the biological machinery required to construct an animal. Perhaps the ancient Earth lacked because complex, many-celled bodies are simply hard to evolve", says Daniel Mills.

His colleagues from the Nordic Center for Earth Evolution have previously shown that have actually risen dramatically at least one time before complex life evolved. Although plenty of oxygen thus became available it did not lead to the development of . Read more about this work here.

Explore further: Atmospheric oxygenation three billion years ago

More information: "Oxygen requirements of the earliest animals," by Daniel B. Mills et al. PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1400547111

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j1mcross
1 / 5 (2) Feb 17, 2014
So when did we consider a sponge complex life?

It might have been animal but complex?
verkle
1 / 5 (13) Feb 17, 2014
Theory on evolution challenged: Life may have been created after all


If you really want an open mind....
Jaeherys
5 / 5 (8) Feb 17, 2014
Sponges are considered complex for a few reasons:

-> multicellular
-> multiple cell types that differentiate from progenitor stem-like cells
-> simple tissues
-> extra and intracellular digestions (most filter feeders)
-> sexual/asexual reproduction
-> colony formation with many members of different types, e.g. digestion, reproduction, defense

The rest is all in the cell and molecular biology. Sure they aren't as complex as insects but they are much more complex than single celled organisms. There's also some very key changes in sponges that may have been important for multicellular organism development and the beginnings of innate immunity.

As a side note, even when we say simple life forms, it doesn't mean they function in simple ways :P. Pretty much every form of life is very complicated, it's just some are way, way more complicated.
AeroSR71
5 / 5 (6) Feb 17, 2014
Theory on evolution challenged: Life may have been created after all


If you really want an open mind....


When someone publishes a scientific thesis in a peer-reviewed journal which may be appropriately tested in the field and offer conclusive evidence, than yes, my mind will undoubtedly be open.
philw1776
5 / 5 (1) Feb 17, 2014
Fascinating example of settled science, unsettled by data. It's great when someone questions the established paradigm and overthrows it. Doesn't happen too often because usually in science the established view is correct having previously passed myriad tests of falsification, but not always. The deep biological past is fascinating and I'm sure holds continued surprises for the clever pure scientist.
philw1776
5 / 5 (3) Feb 17, 2014
Sponges are considered complex for a few reasons:

-> multicellular
-> multiple cell types that differentiate from progenitor stem-like cells
-> simple tissues
-> extra and intracellular digestions (most filter feeders)
-> sexual/asexual reproduction
-> colony formation with many members of different types, e.g. digestion, reproduction, defense

The rest is all in the cell and molecular biology. Sure they aren't as complex as insects but they are much more complex than single celled organisms. There's also some very key changes in sponges that may have been important for multicellular organism development and the beginnings of innate immunity.

As a side note, even when we say simple life forms, it doesn't mean they function in simple ways :P. Pretty much every form of life is very complicated, it's just some are way, way more complicated.


Thanks for the education
jyro
3 / 5 (2) Feb 17, 2014
So climate change produced more complex life?
yep
3 / 5 (2) Feb 17, 2014
"The Cosmic Serpent -DNA- and the Origins of Knowledge" by Jeremy Narby
Pretty interesting read.
Mind boggling the biotechnology that DNA represents.
Kron
1.3 / 5 (3) Feb 18, 2014
Sorry Jaeherys, sponges are far from complex organisms. On the scale of evolution, a sponge is only one step up from an amoeba. If you want to say that all organisms are complex, that is fine, but comparatively speaking, sponges are just about as simple as an organism gets.
Kron
1 / 5 (2) Feb 18, 2014
It is fun to fantasize what a complex creature living in such a low oxygen environment might look like though. A husky burns 240 ml of oxygen per minute per kg of mass. A creature living in a such an environment with a similar vo2 max would require a huge lung surface area.
Lex Talonis
3 / 5 (4) Feb 18, 2014
It is fun to fantasize what a complex creature living in such a low oxygen environment might look like though. A husky burns 240 ml of oxygen per minute per kg of mass. A creature living in a such an environment with a similar vo2 max would require a huge lung surface area.


Yes but sponges only need to sit there, grow slowly over thousands of years, and feed themselves.... with what floats past.
antialias_physorg
5 / 5 (4) Feb 18, 2014
One of science's strongest dogmas

Just for the record: There is no such thing as 'scientific dogma'. A dogma is an argument from authority and incontrovertible. Science doesn't work that way. There may be things that are accepted throughoutthe scientific community - but that only goes as long as no contradictory evidence surfaces.

If you really want an open mind....

Letting everything dribble out and stuffing a sky fairy back in is not the definition of an 'open mind'.

So climate change produced more complex life?

Yes. Slow(!) climate change furthers speciation. Quick climate change (the type we're seeing today) is too much for mutation and selection to handle in most cases. So species just die out. Adaptation takes time.
Osteta
Feb 18, 2014
This comment has been removed by a moderator.
alfie_null
5 / 5 (4) Feb 18, 2014
If you really want an open mind....

Get the irony in this? Coming from someone oh-so-set in his ways. This guy who never asks questions, never seeks the knowledge of others, never has shown any evidence of listening to others, or changing his views. Someone who is so utterly convinced he is right and everyone else is wrong.
Osteta
Feb 18, 2014
This comment has been removed by a moderator.
Torbjorn_Larsson_OM
5 / 5 (4) Feb 18, 2014
@j1mcross: "So when did we consider a sponge complex life?".

It is a complex multicellular life form. Multicellular life forms have evolved 25+ times, of those 6-8 are complex (varieties of algae, plants, fungi and animals).

In addition to what Jaeherys lists, sponges have a body plan, a Hox box. Like parasites, sponges may have been simplified. Earlier this year the first sequencing of comb jellies (chtenophores) showed that they most likely evolved earlier. They have tissues, up to the point that they have evolved muscles independently.

@Kron: "one step up from an amoeba."

You are completely unaware of or misunderstanding the biological technical sense of complex vs multicellularity, as well as of the phylogeny of sponges, see above.
Torbjorn_Larsson_OM
5 / 5 (3) Feb 18, 2014

@phil: "settled science, unsettled by data".

It wasn't settled, nor was the phylogeny of animals I describe above. These things, as well as the unsettling of believed settled science, happens all the time. Re black hole "fire walls" last year (CEP was main stream for 20 years), or the discovery of an Hadean/Archean strong non-OO oxidant (likely NO) recently.

************
Observation on the thread:

Creationist anti-scientists commenting on science are helpful, because they make deconverts from magic beliefs, see Dawkins's Convert's Corner.

And when will they ever make a claim that we can respond to? Claims without evidence are simply rejected without evidence. So there's nothing scientific here to respond to.
antialias_physorg
5 / 5 (2) Feb 18, 2014
proponents like you are violating their own rules all the time.

In what way? It's not like scientists don't look at alternative explanations and dismiss them out of hand.
However, if they look at them and find them to be erroneous then they dismiss it. That's just what you do with wrong theories.

For example, the expanding universe, absence of aether, perpetuum mobiles or cold fusion and evolution are scientific dogmas today.

Expanding universe meshes well with observation (better than anything else). Aether does not mesh with observation. Perpetuum mobiles do not mesh with observation. Cold fusion does also not mesh with observation. And all of these things scientists HAVE looked at and experimented on.

So what are you blathering about?
Osteta
Feb 18, 2014
This comment has been removed by a moderator.
Osteta
Feb 18, 2014
This comment has been removed by a moderator.
Kron
1 / 5 (2) Feb 18, 2014
Modernmystic
5 / 5 (3) Feb 18, 2014
@Torbjorn_Larsson
http://www.mauioc...nges.pdf


If you read that carefully it proved his point...not your assertion...
Kron
1 / 5 (2) Feb 18, 2014
He quoted: one step up from an amoeba, out of my text. If you read the link, you'll find that line in there. I'm not saying that this is literally true, I'm saying it to illustrate the simplicity of it as an organism. Anyone saying otherwise has watched one too many episodes of Spongebob square pants.
Modernmystic
5 / 5 (3) Feb 18, 2014
He quoted: one step up from an amoeba, out of my text. I'm not saying that this is literally true, I'm saying it to illustrate the simplicity of it as an organism. Anyone saying otherwise has watched one too many episodes of Spongebob square pants.


A single cell is incredibly complex in my opinion. In Darwin's day they were thought to be very simple...and then our microscopes got more powerful. A single cell can have potentially thousands of chemical reactions happening all the time. ANY multi-cellular life is absolutely complex life.
Returners
1 / 5 (5) Feb 18, 2014
When someone publishes a scientific thesis in a peer-reviewed journal which may be appropriately tested in the field and offer conclusive evidence, than yes, my mind will undoubtedly be open.


Given enough time and money, human beings could create a replica of a living cell using only non-organic molecular matter. We know what the molecules are, it's just a matter of replicating them manually and putting them in the right place.

Such a thing will most likely be done within the next century.

What will that prove?

It will prove that it is actually a lot easier to create a life form through intelligent process than for such a life form to arise by accident or chance. Occam's Razor therefore suggests that creation is the more sensible view to hold.

They can start with Carbon, hydrogen, oxygen, nitrogen, phosphorous, sulfur, and some trace elements, in elemental form, and they'll probably be able to replicate a yeast cell from scratch within 100 years.
Returners
1 / 5 (4) Feb 18, 2014
The irony is that it will probably be an "abiogenesis believing atheist" who performs the above experiment, not realizing he'll be offering the world at least one piece of the solid proof that it is easier to create a life form from scratch by intelligence than it is to arise by accident and chance.

He will then be force to acknowledge that his own creed, "the simplest explanation that works is the best one," forces him to consider creation a much simpler explanation, an explanation which actually works by experiment, therefore creation is the best explanation of the origins of life.

It's not that far of a leap from existing technologies. The main things we lack are computing power and microscopy: mainly in how it works, not in the scale since they can already see individual atoms as parts of molecules.

Worst case scenario, computing power is achieved by just making larger and larger super computers and networks.
Osiris1
1 / 5 (3) Feb 18, 2014
Ever hear of panspermia? Sometimes we get the l'il hitchhikers on asteroids...and sometimes we do not. In recent years in humano-archaeologic time repeated instances of successful panspermia may have been the source of exotic life, weird cells, diseases, etc. Ya' gotta' be simple to hitch a ride on an itinerant asteroid in the cold of space
Osiris1
1 / 5 (3) Feb 18, 2014
Actually, creation is possible inasmuch as we humans were in all likelihood bioengineered from an existing species over ten thousand years ago. Just look at our archaeological record. We did nothing but chuck rocks and 'chase wimmen' for millions of years. Our only addition to science in those years was making fire and sharpening flint. Suddenly between 14,000 years ago to10,500 years ago we get pyramids in Africa and all over the world, and cities in Turkmenistan laid out in square blocks with real houses of lumber and fired brick complete with running water and indoor plumbing and sewage handling running to pipes under paved streets. This was tech that we forgot after the fall of the Roman Empire in both parts and it stayed forgotten for over a thousand years. And now our progress is accelerating progressively. Someone DID modify us. Someone DID give our lower species an energy field known as a soul. This Great Commission to spread God the original creator comes now to US.
Torbjorn_Larsson_OM
not rated yet Feb 19, 2014
I went back to this as a ref for the "Boring Billions" news comments, but then I remembered re sponge sophistication these recent news on how sponges "sneezes" (with video):

http://www.thebla...y-human/

""[…] the finding of such an organized array of sensory cells in sponges provides new insight into possible mechanisms of evolution of early sensory systems," the study concluded.

"This is a very exciting and comprehensive study that clearly demonstrates that sponges are more sophisticated," said sponge expert with the University of Munich Gert Worheide, who was not involved with this study, said, according to National Geographic."
Torbjorn_Larsson_OM
5 / 5 (2) Feb 19, 2014
I repeat:

Creationist anti-scientists commenting on science are helpful, because they make deconverts from magic beliefs, see Dawkins's Convert's Corner.

And when will they ever make a claim that we can respond to? Claims without evidence are simply rejected without evidence. See Returner's idea of assembling modern cells from elements, which is akin to assembling the modern Earth from asteroids. It won't happen; but if it does come back for analysis.

So there's nothing scientific here to respond to. Except this:

@Kron: "He quoted: one step up from an amoeba, out of my text. If you read the link, you'll find that line in there. I'm not saying that this is literally true, I'm saying it to illustrate the simplicity."

In my first comment I noted how the phylogeny of sponges is changed, they split well after. Comb jellies are likely (not settled, but the best phylogeny at the moment) closer to choanoflagellate amoeba. But they have evolved muscle tissue etc.
Bonia
Feb 19, 2014
This comment has been removed by a moderator.
Torbjorn_Larsson_OM
5 / 5 (1) Feb 19, 2014
Bonia, good question! These results, as well as the pyrite results, are arguable. They assume a tension to previous results, where some (most, I think) come down on the side of little early (Archean) oxygen both from geochemistry and from biology (phylogenies), some on the side of some.

As I commented on the Boring Billions article (thanks for the link!), it is barely a tension between their ~ 0.2 % oxygen of that work and these ~ 0.5 %. But note I extracted that figure from the image, so it needs to be checked and they may give more precise values in their paper. (It's now on my reading list.)

I also provided a ref to a recent pyrite analysis of sulfur isotopes (as well as those phylogenies showing little early oxygen), that extract from several sources a more complex model of its formation than the paper here may take into account. To pinpoint exactly the lower limit of possible oxygen isn't easy then.

This is a contribution to that analysis, not a definitive result.
Torbjorn_Larsson_OM
5 / 5 (1) Feb 19, 2014
[cont] All this has implications for theories of a) mitochondrial eukaryote lateness and b) animal suddenness (Cambrian explosion).

The anoxic, sulfidic Canfield ocean mode I described over on the BB thread is one among other factors that figures into both. The sparsity of the Edicarian fossil record may be because of that, the deep oceans had sparse oases for life. (See ref on the BB thread.)

From independent estimates, eukaryotes may have split from the archaea right after the UCA split into archaea and bacteria, but they didn't undergo the bacterial mitochondrial endosymbiosis until ~ 1 billion years ago. This is either inside the BB period, or after the oxygen began to rise to modern levels.
Torbjorn_Larsson_OM
5 / 5 (1) Feb 19, 2014
[cont] Speculation from my side:

Since amitochondriate eukaryotes are extinct, I would now think the oxygen stress that killed an estimated 99 % of all life and made deep phylogeny such a mess happened after the endosymbiosis. The pre-event oxygen was enough to enable it, and afterwards it may be that the rising oxygen killed those eukaryotes that wasn't pre-adapted to oxidant stress by having mitochondria.

Archaea and bacteria may have managed because they have examples of vast populations to adapt from.

Such a scenario is among those that make people ask: why were mitochondrial eukaryotes late? It may have taken ~ 2 billion years (see the BB thread graph) of oxygen presence. One hypothesis is that it is rare, having astrobiological implications. (E.g. many planets with life, fewer with complex multicellulars.)