What if multiple kinds of original life arose simultaneously?

[Aubs]

*Let me preface this post by saying I'm a firm believer in evolution, I'm not trying to "disprove" evolution or anything of that nature*

 

Okay, so usually when evolution is presented alongside cladograms and web-like visual representations of evolution over time, there seems to be an implied consensus that, at some point, there had to have been some original one-celled species from which all subsequent life evolved.

 

However, is it implausible that, perhaps, life arose independently at different geographic locations on the planet? What I'm saying is that say a species of one-celled organism arose in the primordial ooze somewhere in the southern hemisphere. Now what if another species of one-celled organism arose (completely independent of the first) in the northern hemisphere. In this hypothetical situation, there would then be two evolutionary lineages rather than one.

 

Has it been proven that there really is a single evolutionary lineage (I'm genuinely curious)? Is it even possible to know? Have scientists studied this? Are there any scientific ramifications of there being multiple evolutionary lineages, or is it just interesting food for thought?

Edited December 25, 2011 by Aubs

[Ringer]

Although we don't, and probably can't, really know if there was a single original organism the best guess is we come from a single common ancestor. The similarities between all living organisms would be very unlikely if we developed from different sources.

[Greg Boyles]

Although we don't, and probably can't, really know if there was a single original organism the best guess is we come from a single common ancestor. The similarities between all living organisms would be very unlikely if we developed from different sources.

 

This is pretty close to be a seperately evolved form of life on planet Earth.

 

The Archaea (/ɑrˈkiːə/ ( listen) ar-kee-ə) are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon (sometimes spelled "archeon"). They have no cell nucleus or any other membrane-bound organelles within their cells.

 

In the past they had been classed with bacteria as prokaryotes (or Kingdom Monera) and named archaebacteria, but this classification is regarded as outdated.^[1] In fact, the Archaea have an independent evolutionary history and show many differences in their biochemistry from other forms of life, and so they are now classified as a separate domain in the three-domain system. In this system, the phylogenetically distinct branches of evolutionary descent are the Archaea, Bacteria and Eukaryota.

 

Archaea are divided into four recognized phyla, but many more phyla may exist. Of these groups, the Crenarchaeota and the Euryarchaeota are the most intensively studied. Classification is still difficult, because the vast majority have never been studied in the laboratory and have only been detected by analysis of their nucleic acids in samples from the environment.

 

Archaea and bacteria are quite similar in size and shape, although a few archaea have very unusual shapes, such as the flat and square-shaped cells of Haloquadratum walsbyi. Despite this visual similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably the enzymes involved in transcription and translation. Other aspects of archaean biochemistry are unique, such as their reliance on ether lipids in their cell membranes. Archaea use a much greater variety of sources of energy than eukaryotes: ranging from familiar organic compounds such as sugars, to ammonia, metal ions or even hydrogen gas. Salt-tolerant archaea (the Haloarchaea) use sunlight as an energy source, and other species of archaea fix carbon; however, unlike plants and cyanobacteria, no species of archaea is known to do both. Archaea reproduce asexually by binary fission, fragmentation, or budding; unlike bacteria and eukaryotes, no known species form spores.

 

Initially, archaea were seen as extremophiles that lived in harsh environments, such as hot springs and salt lakes, but they have since been found in a broad range of habitats, including soils, oceans, marshlands and the human colon. Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are now recognized as a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle. No clear examples of archaeal pathogens or parasites are known, but they are often mutualists or commensals. One example is the methanogens that inhabit the gut of humans and ruminants, where their vast numbers aid digestion. Methanogens are used in biogas production and sewage treatment, and enzymes from extremophile archaea that can endure high temperatures and organic solvents are exploited in biotechnology.

Edited December 26, 2011 by Greg Boyles

[dimreepr]

*Let me preface this post by saying I'm a firm believer in evolution, I'm not trying to "disprove" evolution or anything of that nature*

 

Okay, so usually when evolution is presented alongside cladograms and web-like visual representations of evolution over time, there seems to be an implied consensus that, at some point, there had to have been some original one-celled species from which all subsequent life evolved.

 

However, is it implausible that, perhaps, life arose independently at different geographic locations on the planet? What I'm saying is that say a species of one-celled organism arose in the primordial ooze somewhere in the southern hemisphere. Now what if another species of one-celled organism arose (completely independent of the first) in the northern hemisphere. In this hypothetical situation, there would then be two evolutionary lineages rather than one.

 

Has it been proven that there really is a single evolutionary lineage (I'm genuinely curious)? Is it even possible to know? Have scientists studied this? Are there any scientific ramifications of there being multiple evolutionary lineages, or is it just interesting food for thought?

 

The double helix is the fundamenal of life. This idea means we would have more than one solution to this fundamental, and the only solution we have found is the double helix.This means it is very unlikely that this is true. It doesn't rule out the idea just makes it much less likely.

Edited December 26, 2011 by dimreepr

[Ringer]

This is pretty close to be a seperately evolved form of life on planet Earth.

 

 

 

I don't follow. Are you disagreeing?

[Greg Boyles]

I don't follow. Are you disagreeing?

 

Was replying to the OP. Merely pointing out that archaebacteria are as close as we are likely to get to a seperately evolved lifeform on planet earth.

 

It probably not clear whether it is truly the case given that both use DNA as their genetic medium but I suppose it would also depend on how different the triplicate codes are between archaebacteria and the other kingdoms.

[kitkat]

Given that eukaryotes origin come from the symbiotic partnership of archae and bacteria in an environment that needed an organism to take in large amounts of oxygen which could compartmentized an area for archae who preferred an environment without oxygen while its partner required the oxygen environment was the perfect solution for the introduction of a planet that was now changed by oxygen waste.

[HuMoDz]

The double helix is the fundamenal of life.

What does that mean, "double helix", is it the dna?

[Greg Boyles]

Given that eukaryotes origin come from the symbiotic partnership of archae and bacteria in an environment that needed an organism to take in large amounts of oxygen which could compartmentized an area for archae who preferred an environment without oxygen while its partner required the oxygen environment was the perfect solution for the introduction of a planet that was now changed by oxygen waste.

 

I am not aware of any theories that involve archae forming symbiotic relationships with bacteria to form eukaryotes. As far as I am aware the theory only ever refered to prokaryotes doing this.

 

Remember that archae have ether lipids forming their cell membranes but both eukarytotes and prokaryotes have phospholipids forming their cell and organelle membranes.

[Moontanman]

I am not aware of any theories that involve archae forming symbiotic relationships with bacteria to form eukaryotes. As far as I am aware the theory only ever refered to prokaryotes doing this.

 

Remember that archae have ether lipids forming their cell membranes but both eukarytotes and prokaryotes have phospholipids forming their cell and organelle membranes.

 

There is some validity to the idea that archea are ancestral to Eukaryota

 

http://norlx51.nordita.org/~brandenb/astrobiology/docs/Poole+Neumann2011.pdf

 

Abstract

An archaeal origin of eukaryotes is often equated with the engulfment of the bacterial ancestor of mitochondria by an archaeon. Such an

event is problematic in that it is not supported by archaeal cell biology. We show that placing phylogenetic results within a stem-and-crown

framework eliminates such incompatibilities, and that an archaeal origin for eukaryotes (as suggested from recent phylogenies) can be

uncontroversially reconciled with phagocytosis as the mechanism for engulfment of the mitochondrial ancestor. This is signicant because it

eliminates a perceived problem with eukaryote origins: that an archaeal origin of eukaryotes (as under the Eocyte hypothesis) cannot be

reconciled with existing cell biological mechanisms through which bacteria may take up residence inside eukaryote cells.

2010 Institut Pasteur. Published by Elsevier Masson SAS. All rights reserved.

 

There is also the idea of a "shadow biosphere" made up of organisms from a separate origin of life.

 

http://www.dailygalaxy.com/my_weblog/2009/07/is-there-undiscovered-weird-life-on-earth-worldleading-expert-says-it-could-be-biggest-discovery-sin.html

Edited December 28, 2011 by Moontanman

[Greg Boyles]

There is some validity to the idea that archea are ancestral to Eukaryota

 

http://norlx51.nordi...Neumann2011.pdf

 

 

 

There is also the idea of a "shadow biosphere" made up of organisms from a separate origin of life.

 

http://www.dailygala...covery-sin.html

 

Without reading the paper I find it difficult to understand how they would account for such a fundamental difference between cell membrane structure.

 

As I ubderstand it all Archae have etherlipid membranes and all prokaryotes and eukaryotes have phospholipid membranes. Etherlipids because they are more stable in extreme environmental niches where the archae are always found.

[Moontanman]

Without reading the paper I find it difficult to understand how they would account for such a fundamental difference between cell membrane structure.

 

As I ubderstand it all Archae have etherlipid membranes and all prokaryotes and eukaryotes have phospholipid membranes. Etherlipids because they are more stable in extreme environmental niches where the archae are always found.

 

 

To be honest I think you should read the paper....

[Greg Boyles]

To be honest I think you should read the paper....

 

IT merely suggests an alternative means of evolution of eukaryotes, i.e. archae engulfing a prokaryote which becomes the mitochondria of a eukaryote, but provides no evidence for how this could have happened. Apparently to account for the fact that archae and eukaryotes are more closely related than they are to prokaryotes. Interesting but.....

[CharonY]

I am not aware of any theories that involve archae forming symbiotic relationships with bacteria to form eukaryotes. As far as I am aware the theory only ever refered to prokaryotes doing this

 

Actually this is close to the standard theory for the origin of eukaryotic cells. In fact, the similarities found between archaea and eukaryotes was one of the big problems placing archaea properly in a taxonomic model. Current assumption based on molecular data posits that early eukaryotic cells were derived by association of distinct archaeal and bacterial partners.

 

Also note that archaea and bacteria are both prokaryotes.

Edited December 29, 2011 by CharonY

[Greg Boyles]

Actually this is close to the standard theory for the origin of eukaryotic cells. In fact, the similarities found between archaea and eukaryotes was one of the big problems placing archaea properly in a taxonomic model. Current assumption based on molecular data posits that early eukaryotic cells were derived by association of distinct archaeal and bacterial partners.

 

Also note that archaea and bacteria are both prokaryotes.

 

 

Currently, textbooks from the United States use a system of six kingdoms (Animalia, Plantae, Fungi, Protista, Archaea and Bacteria)

 

Granted but they are not classified in the same kingdom.

[Moontanman]

Currently, textbooks from the United States use a system of six kingdoms (Animalia, Plantae, Fungi, Protista, Archaea and Bacteria)

 

 

 

Actually they use the three domain system now, the six kingdoms is not considered accurate now.

 

 

http://en.wikipedia.org/wiki/Three-domain_system

 

[dimreepr]

What does that mean, "double helix", is it the dna?

 

 

Yes it's the structure of dna.