Why only one source of life

I have posted the following question on this board before and have never received a very good answer. Perhaps there is someone on this board with enough technical knowledge who can provide a good reply. Also I would like to hear from anyone who would like to speculate what the answer might be. My question: Why is there only one phylogenetic tree when one would expect several phylogenetic trees. To reply that all life one earth is descended from a single source is not the answer. My question is why only a single source.

To expound further on the question, Douglas Theobald in his thesis "The Scientific Case for Common Descent" www.talkorigins.org/faqs/comdesc/makes the case that all living organisms on earth are descended from a single source (and if you "read between the lines" perhaps even a SINGLE organism.) To quote Dr. Theobald:

According to the theory of common descent, modern living organisms, with all their incredible differences, are the progeny of one single species in the distant past.

In short Theobald's contention is that the vertebrates, the invertebrates, plants, trees, lions, tigers, ostriches, apes, men, fungi, etc. all have a common ancestor, a SINGLE origin. Dr. Theobald describes a phylogenetic tree which traces all living organisms from this single source. For example vertebrates and invertebrates are supposed to have descended from a more ancient ancestor. That more ancient ancestor came some more ancient ancestor, etc. This tree traces back to a single point, a single organism which made the abiogenetic jump from non-living to living (perhaps one complex molecule 3.5 billion years ago). Theobald in his monograph does not delve into abiogenesis (the origins of life from inanimate material); he starts with the common ancestor of all life. In his paper, Theobald does not consider theories on abiogenesis, just that it happened. Again quoting Dr. Theobald:

Furthermore, because it is not part of evolutionary theory, abiogenesis also is not considered in this discussion of macroevolution: abiogenesis is an independent hypothesis. In evolutionary theory it is taken as axiomatic that an original self-replicating life form existed in the distant past, regardless of its origin. All scientific theories have their respective, specific explanatory domains; no scientific theory proposes to explain everything.

The logical conclusion of Theobald 's paper is that the event of abiogenesis (living replicating organisms arising out of non-living matter) happened ONLY ONCE in the 4.5 billion year history of the earth. Indeed if abiogenesis happened more than once, then we should see more than one phylogenetic tree tracing back to several common ancestors with totally different characteristics (such a completely different DNA makeup).

However current theories of abiogenesis state that living organisms must arise out of the conditions of the early earth. That this event (the abiogenetic jump from non-living to living) must happen in these conditions and is an event which happens often enough to guarantee the generation of living organisms over a relatively short period of time (on a geological scale, say less than 500 million years). In other words, if we have enough naturally occurring proteins in a primordial soup, enough are going to combine together to eventually form living organisms. Current theories sate that the oceans formed 3.8 billion years ago; beginning of photosynthesis by blue-green algae started 3.5 billion years ago. Life jumped from nothing (3.8 billion years ago) to algae (3.5 billion years ago) in a period of about 300 million years. Algae are several orders of magnitude more complex than protein molecules. This suggests then that abiogenesis should be a relatively common event in the early conditions of the earth (in short life forms started firing up as soon as the earth cooled enough to permit life). This then leads one to the conclusion that there should be several phylogenetic trees which can be traced back to different organisms which made this abiogenetic jump . In other words, today we should be seeing living organisms who are totally different from one and and other (such as animals who use a completely different DNA makeup than ours).

Now as a believer in Intelligent Design, I have no problem with Common Descent. It just proves that God created all life on earth from a single spark of life generated from inanimate material. In other words, God was very frugal in the generation of life on earth. He did not need to create a blizzard of organisms from inanimate material to generate life on this planet, He did the job with just one.

So my question to the Darwinists is:

In Common Descent you state that life on earth arose from a single source. You do not really address the issue of abiogenesis. However you do state that living matter must naturally arise out of the environment of the early earth. If this event naturally occurs, then a whole bunch of different organisms should then develop in these conditions and lead eventually (today) to living creatures who a fundamentally different from each other. Then why is the only one kind of basic life on this earth when there should be many.
Why only one source of life

[edit on 26-2-2008 by jagdflieger]

[edit on 26-2-2008 by jagdflieger]

Originally posted by jagdflieger
In Common Descent you state that life on earth arose from a single source. You do not really address the issue of abiogenesis. However you do state that living matter must naturally arise out of the environment of the early earth. If this event naturally occurs, then a whole bunch of different organisms should then develop in these conditions and lead eventually (today) to living creatures who a fundamentally different from each other. Then why is the only one kind of basic life on this earth when there should be many.
Why only one source of life

Hi jag,

First things first. The issue of abiogenesis is separate from the theory of evolution and common descent. Thus, knowing that you are a IDer, your divine biochemist could have poofed the first organism into existence using his mind, and then evolution by natural selection take over to produce what we see today.

Given, that's not really accepted by many people in the field, but evolution doesn't eliminate this possibility.

So, the second part is mainly related to the notion that life has a single common ancestor. I suppose it's not impossible for there to be more than one. Indeed, some already do question the notion of a single-common ancestor for all life - a single phylogeny, especially at the level of single-celled organisms and viruses.

But what appears to be the case is that modern species are genetically related, suggesting a single phylogeny. But maybe we might find evidence of different classes of life that are unrelated by phylogeny to known species, here on earth and/or elsewhere in the cosmos. Time will tell.

Hwyl fawr

[edit on 26-2-2008 by melatonin]

Reply to melatonin.

First I realize that the issue of abiogensis is considered a seperate issue from common descent. However until the two issues are intergreted with answers, life scientists still lack some basic understanding of how life formed on this planet. To me it is akin to cosmologists stating that we really understand this universe without explaning the Big Bang, what is Dark Matter, what is Dark Enegry. In short we do not have a true understanding of what is going on until these sort of questions are answered. Notice that the scientists are examining only micobes. (Yes I did read the article - quite interesting). Notice that nothing yet has been discovered that con be traced to a seperate phly

reply to post by melatonin

First I realize that the issue of abiogensis is considered a seperate issue from common descent. However until the two issues are intergreted with answers, life scientists still lack some basic understanding of how life formed on this planet. To me it is akin to cosmologists stating that we really understand this universe without explaning the Big Bang, what is Dark Matter, what is Dark Enegry. In short we do not have a true understanding of what is going on until these sort of questions are answered. Notice that the scientists are examining only micobes. (Yes I did read the article - quite interesting). Notice that nothing yet has been discovered that can be traced to a separate phlygeny. Also it leads to the question, "If microbes exist which can be traced to a separate "genesis", then why did these microbes not evolve into more advanced life forms?"

Originally posted by jagdflieger
Also it leads to the question, "If microbes exist which can be traced to a separate "genesis", then why did these microbes not evolve into more advanced life forms?"

Maybe because they became so specialised and adapted to one environment, that they couldn't move to a different one. I don't know. It's all a bit hypothetical at this point, hard to make any claims when it's just a possibility with no evidence.

So, say that some microbes evolved independently that survive in extreme conditions, so living off an sulphurous uundersea plume. for instance - maybe they can't survive away from this environment.

All total speculation, of course.

We do lack understanding of how life formed, especially at the abiogenetic stage. Indeed, we don't even have perfect knowledge of evolution, we have enough to know with a good degree of certainity it happened, but I'm sure there's still surprises to be found. That's the beauty of science. Always more questions and answers.

[edit on 26-2-2008 by melatonin]

here are a few things that came to mind that i've learnt throughout my biological studies.

-atmosphere change. once oxygen became rich in the atmosphere, organic molecules become a lot more unstable if not membrane bound. oxygen was even considered toxic to primitive life (oxidation). us humans try and prevent free oxygen radicals from damaging our bodies with antioxidants, but as expected our body has proteins in place to soak up some of them, which is considered rather complex compared to primitive life.

-once "life as we know it" was established it out competed any of these competitors.

-these "other forms of life" were around in the past but became obsolete if you like, and weren't really in high abundance/didn't fossilize easily.

-the environment of earth was only specialized for the kind of life we see.

-only one type of life exists/is successful. RNA world -> DNA world.

still not entirely sure what your asking, because as i see it life is mind boggling diverse with what seems like endless body plans. are you referring to why do we have carbon based life opposed to silicon based life and carbon? or why we are so dependent on water opposed to other liquids? or why our food chain is dependent on radiant energy (minus deep vent communities)? or why are fundamental building blocks of biological molecules mostly carbon, hydrogen, oxygen, nitrogen, phosphorus?

if you could be more specific i'd like to further the discussion.

[edit on 27/2/08 by cheeser]

Originally posted by jagdflieger
Also it leads to the question, "If microbes exist which can be traced to a separate "genesis", then why did these microbes not evolve into more advanced life forms?"

please explain what you mean by advanced.

by microbes do you mean singular celled organisms?
take the protozoans for an example, they are single celled animals if you like, some predators some scavengers, much more diverse than the metazoans (multi celled animals). these single cells are with no doubt much more complex, multi functional than any single cell i can think of in the human body (minus the actual protozoans that parasitically live inside some of us). some biologists will look at the human body as just a collection of specialized single celled organisms, a super colony of cells if you like working together to survive and procreating their genetic material.
-if you have this outlook on it, then the "microbes" by themselves are more complex on their own than any of the single "microbes" that work together in this super colony called a human.

"more advanced lifeforms" - life can only get so far advanced, or.. it may not be an advantage to be more advanced. the more specialized an organism is, the less likely it will be able to cope with change in the environemt. you could argue that humans are exclusive of this principle.

so whats more advanced? microbes or multicellular life?
-they both are successful, both still exist.
-protozoan cell vs metazoan cell, the protozoan cell is more complex (microbe) in most cases.

i know this wasn't directly answering your question, i realized i went a bit off track when i re-read your post but maybe it still could shed some light on your question.


[edit on 27/2/08 by cheeser]

I haven't read the replies, so if someone has covered this already, ignore this post.

My first thought would be predation. Its not so hard starting out as a proto-lifeform if there is nothing else around that is trying to end what you just started.

Being newly-fabricated and (without any evolutionary steps of your own so far) then being forced to compete for resources with an excellently-established ecosystem is doomed to faliure, in my opinion.

I think once a life form developed (in 300 million year intervals, by your post), in another 300 million years, the extant life forms were too abundant for the new attempt.

Who knows, eh?

well, if life has multiple sources, those sources have sources, and those sources also have sources, but as you go down the tree from now to life's beginning, all of life, all of matter HAS to have one source. I guess that's not really the direction you are going with this.

You are talking about life here on Earth SPECIFICALLY?

If so, well then abiogenesis makes perfect sense. Some early life could have come from different asteroids and comets, some could have formed from the right mixture of compunds naturally in our seas, and still others could have been genetically engineered by intelligent beings, OR by consciousness as a whole, OR creatures could just randomly becxome existant through some random coalescence of thought, or through some quantum accident that we can't even understand with human brains....

This is a massive question, but I think life originating on Earth from multiple sources is a safe assumption. Life is so varied here, ya know? It's hard to imagine that a single cell gave way to the whole ecosystem.... but maybe that's what happened. We can't really know, unless someone we could trust happened to have been around 2-3 billion years ago when this all started, and they could relate their observations back to us somehow. That would mean either he's a couple billion years old, or he has a time machine. I don't have cool friends like that.