Talk:Common descent

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[edit] Studying phylogenetics

I'm studying phylogenetic trees right now, and it occured to me that our ability to produce consistant trees using parsimony analysis is good evidence of common descent. Parsimony analysis is distinct from similarity based phylogeny construction because it explicity tries to recreate the path along which the molecules evolved. As a consequence, it is capable of distinguishing between similarity by convergence and similarity by descent. So first, I object that the ability to create phylogenetic trees based upon similiarity is evidence of common ancestory. Second, I think that this article should directly mention cladistic methods of phylogeny construction, and not just reference the phylogenetics article. adam

Cladistic analysis is based on the principle of maximum parsimony, i.e. diagrams that requires the least number of evolutionary changes. It is the most compact arrangement. One drawback to this approach, as you mention, is that evolution does not always occur along a minimum path. To some biologists, the term "cladogram" emphasizes that the diagram represents a hypothesis about the actual evolutionary history of a group, while "phylogenies" represent true evolutionary history. Cladograms show the divergence of character traits but do not imply an evolutionary time-line. Yes, cladistics should be introduced here, and not phylogenetic trees. Cladograms are based on the most common ancestor and show the derived characterics that occurred. By contrast, phylogenetic trees show the evolutionary branching. The former belongs here, the later in evolution. Introducing phylogenetic trees here, as a purported proof, muddled up the article. Phylogenetic trees show evolution, not common descent or common ancestry.
This article requires extensive categorical reworking to address the correct subject, i.e. common descent, not evolutionary timelines, not LUCs and LUCAs, and not origin of life issues. Valich 01:46, 20 March 2007 (UTC)

A common type of ancestor, right? I mean, maybe all life evolved from the same type of single-celled organisms that, it so happens, originated in several different places in the world--not necessarily from the exact same ancestor. Or does it really mean from the exact same ancestor?

Good to see you hear, John! --LS

As I have seen the term used, it does indeed mean that all observed life descended from the very same ancestor, which is actually quite likely given the nature of speciation and the brutal pruning of the tree of descent. I include the weasel-word there because we know so little about what might have started the process in the first place that we can barely even speculate about forms of life earlier than those we have seen. Since we have not seen any replicator sufficiently simple to have conceivably arisen spontaneously (we only assume there was one), all those we have seen are products of reproduction as we see it now, so they are almost with mathematical certainty descended from a single individual. Even if similar mutations or chance events had arisen independently early on, it is mathematically likely that only one survived (it is even more likely that none would, but obviously at least one did). -- Lee Daniel Crocker
Yes, LUCA is presumed to be one particular organism, not a group of organisms. If you are looking for the common ancestors of humans (an obligate sexual reproducer), then you are probably going to find a group of individuals. However, if the ancestor is a single cell capable of clonal replication, as LUCA presumably is, then I would only expect to find one ancestor. Going on this model, LUCA would have had "siblings and cousins" that existed at the same time as it, but those lineages went extinct either by chance or because the LUCA lineage included some innovation that allowed it to displace the other lineages. adam

Shouldn't this article be merged with the article on LUCA (Last universal common ancestor)? They cover precisely the same topic. We should move all the text from one into the other, and then turn the empty article into a redirect. RK 16:53, 1 Sep 2003 (UTC)

There were several theories of 'common descent' that were not theories of 'universal common descent'. I will try to fix this article accordingly but in the meantime, "Common Descent" and "LUCA" should be kept separate.Peak 04:14, 5 Dec 2003 (UTC)
No. Just the opposite. This article should surrender all of its content over to the LUCA and LCA article and focus on the subject of common descent and commonm ancestry.Valich 01:46, 20 March 2007 (UTC)

[edit] History

Pierre-Louis Moreau de Maupertuis' account of divergence through random variation and natural selection sounds very much to me like something that Empedocles said much earlier. [1] I thought it should be included, but I didn't want to be presumptuous. Neopergoss 05:38, 4 December 2006 (UTC)

[edit] "Common descent" usually means "Universal common descent"

In scientific and general parlance, unless specified otherwise, "common descent" and "universal common descent" are essentially synonymous. "Common descent" gets about 240K google hits, "universal common descent" only gets about 700. The concept of "non-universal common descent" is almost always called "sharing a common ancestor" (~133K google hits, compare to ~7K for "have common descent" -many using it with a different meaning- and <1K for "share common descent"). The fact is worth noting. —Preceding unsigned comment added by Thomas Arelatensis (talk • contribs)

"Common descent" and "universal common descent" are not synonmous because descent is not always from a common ancestor, therefore it is not always universal. The article is about "common descent" and that is what the emphasis should be on. Yet, the subject of "Evidence of universal common descent" appears primary before "Evidence of common descent." Furthermore, if you're going to include phylogenetic trees as evidence for universal common descent, then mention should be equally made that this view is under scrutiny, and the more up-to-date alternative "Ring of Life" phylogenetic diagram and multiple origin concept should be introduced, else get rid of the entire category of "Evidence for a universal common descent. All four concepts introduced to support this concept, actually support common descent, not universal common descent.Valich 00:46, 20 March 2007 (UTC)

[edit] Split

Splitting "common descent" from "universal common descent" is specious at best, and POV at worst. There is no good reason for a split. Guettarda 15:46, 8 February 2007 (UTC)

Concur. Having failed to gain consensus for a move, to create a "split" then edit the copy to reflect one minor POV and ignore balance is a clear example of POV forking. That the POV fork had been proposed and also failed to gain consensus takes this beyond that into a violation of CON as well as NPOV. KillerChihuahua?!? 17:17, 8 February 2007 (UTC)
Concur. That split was bizarre at best.--Thomas Arelatensis 18:48, 8 February 2007 (UTC)
As I stated in the above talk section, this article is about common descent, not universal common descent. This split confuses the subject. Universal common descent leads into talk about Universal Common Ancestor (UCA) Last Universal Common Ancestor (LUCA) or Last Common Ancesor (LCA), and these are unrelated topics that deal with origins of life. They should not even be mentioned here, except for external links. There never was a last universal common ancestor.
Doolittle (1999) states: "In general, the current situation concerning the evolutionary "tree of life" is as follows: The conceptual tree-like structure with discrete branches is retained at the top of the eukaryote domain, and also retained is the idea that eukaryotes obtained mitochondria and chloroplasts from bacteria. But the lower parts of the tree are now seen to involve an extensive anastomosis of branches -- branches joining other branches in a complex network of intersecting links -- resulting from extensive horizontal gene transfer of single or multiple genes, the horizontal gene transfer known to be common in unicellular organisms. Thus, the "tree of life" lacks a single organism at its base, and that "the three major domains of life probably arose from a population of primitive cells that differed in their genes."
Rivera and Lake (2004) point out: In the microbial world things are different, and various schemes have been devised to take both traditional and molecular approaches to microbial evolution into account. Unknown to Darwin, microbes use two mechanisms of natural variation that disobey the rules of tree-like evolution: lateral gene transfer and endosymbiosis. Lateral gene transfer involves the passage of genes among distantly related groups, causing branches in the tree of life to exchange bits of their fabric. Endosymbiosis -- one cell living within another -- gave rise to the double-membrane-bounded organelles of eukaryotic cells: mitochondria and chloroplasts. At the endosymbiotic origin of mitochondria, a free-living proteobacterium came to reside within an archaebacterially related host. This event involved the genetic union of two highly divergent cell lineages, causing two deep branches in the tree of life to merge outright. Instead of a tree linking life's three deepest branches (eubacteria, archaebacteria and eukaryotes), they uncover a ring.
The tree of life, is a ring of like, or a net of life, and it does not have a LUCA or LCA. At the single cell microbial level, there is no such thing as a LUCA or LCA anymore.Valich 01:04, 20 March 2007 (UTC)

[edit] Creationist Orchard Section Split

I think this content is useful but doesn't belong on this page. It should be moved and the only thing I can think of is creationist orchard. Do to previous deletion reviews we should discuss this split before moving it. Pbarnes 19:30, 11 February 2007 (UTC)

This should have at most a sentence or two mention. Arguably any mention on this page runs afoul of WP:NPOV's undue weight clause, and we don't have almost any independent sources dicussing the topic. I would suggest just trimming it to a short section here and knocking out most of the discussed matter (espec in regard to the orchard). JoshuaZ 19:35, 11 February 2007 (UTC)
Is some important information, though, that doesn't fit this article. Mainly the following.
  • The main difference between "universal" common descent and the "creationist orchard" is the change of "genetic information" with time. The creationists that subscribe to the creationist orchard claim that genetic information does not "advance" but instead deteriorates as time progresses. Many creationists claim that God created the various kinds with "perfect genetic information". The fall of man produced pressures similar to natural selection which caused this perfect genetic information to become progressively more degraded. The loss of this perfect genetic information resulted in variations within each species. When these different members of the same species "interbreed", creationists claim the result only resembles evolution but instead only causes a mixing of the imperfect genetic information to produce offspring similar to an original perfect ancestor.
I have yet to find this information anywhere on wikipedia and it is almost required if you ever want to discuss evolution with a creationist. Pbarnes 19:44, 11 February 2007 (UTC)
Try adding it to Created kind as a variant. Adam Cuerden talk 20:02, 11 February 2007 (UTC)
See Wikipedia:Articles for deletion/Orchard Theory - this in non-notable material, and it has already failed AfD. As Adam pointed out, we already have an article on created kinds, this doesn't belong in this article and it most certainly doesn't belong in a separate article. Anything useful should be incorporated into the created kinds article. Stop trying to bypass community consensus. Guettarda 20:13, 11 February 2007 (UTC)

The article is about Common descent - removed creationist stuff and replaced with see also. Vsmith 01:01, 12 February 2007 (UTC)

I've just unarchived this and the preceding section. Discussion that is less than a week old should not be archived. Were we trying to hide something?? Whatever the reason - leavi it here for others to see. Vsmith 01:19, 15 February 2007 (UTC)

[edit] Created Kinds Section Merge

I'm against it, because I don't see the harm in a small, yet informative section like this. People seem to be biased against all forms of creationism. This is completely related to the article and I don't feel it is undue weight given the context. If the article on earth can include references to flat earth, why can't this article refer to certain aspect of creationism? Pbarnes 02:32, 12 February 2007 (UTC)

Because, frankly, this is a modern, manufactured excuse that I doubt even the proponents really believe. Adam Cuerden talk 02:36, 12 February 2007 (UTC)
What do you mean? You believe creationist don't believe what the information describes? Pbarnes 02:38, 12 February 2007 (UTC)
I've had a look at some of their articles on it. They're deliberately obfuscatory, and, since you don't normally write obfuscatory if you have clear reasoning, I strongly suspect these are cynical PR pieces to try and bamboozle people into thinking that it's a valid conclusion they just aren't clever enough to understand, while the creators are likely clearly aware how little substance is in it. Hell, half of it seems to be defining terms so as to make it even harder, and each article invents a few new terms. If not a cynical way of diverting attention from what they're really saying, then what is it? If it is, then why, if they believe it's true, are they carefully concealing their logic in invented terms? Adam Cuerden talk 19:37, 12 February 2007 (UTC)
I don't think this is deliberately obfuscatory. It reads to me more like the products of people who don't know how to write well, don't know how to think logically and don't understand science. JoshuaZ 19:44, 12 February 2007 (UTC)
...That's just sad. Adam Cuerden talk 10:42, 15 February 2007 (UTC)
It doesn't matter if it's merged with created kinds or just deleted (after all, it's content that the community decided was inappropriate for Wikipedia). But it isn't about common descent, and it isn't scientific, it's cruft. Guettarda 02:59, 12 February 2007 (UTC)
Since when was this article determined to be strictly "scientific"? And where was it decided "it's content that the community decided was inappropriate for Wikipedia." Pbarnes 03:08, 12 February 2007 (UTC)
It is science and creationism is religion (or some approximation of it). See the afd referred to above. And it seems you are in violation of WP:3rr, in case you would like to undo your last revert. Cheers, Vsmith 03:18, 12 February 2007 (UTC)

[edit] Vote

Merge, or some other mutually agreeable way to get rid of this section and replace it with a passing mention of creationism. There is no need to devote a whole section to a fringe theory, even less so to explain several microvariations within it. Let us just mention that most creationists deny common descent, except "within kinds", despite massive cross-corroborating evidence (morphological, biochemical, fossil and molecular) in support of it.--Thomas Arelatensis 12:48, 12 February 2007 (UTC)

Keep. That's a little information, and that's the reason for the "main article" link. Why delete? It has to do with the rest of this article. Nethac DIU, would never stop to talk here 17:51, 12 February 2007 (UTC)

Merge it somewhere and remove it from here. Just in case my views weren't apparent before. Seems the concensus is to merge as I read it. Vsmith 01:19, 15 February 2007 (UTC)

And the reasoning for this is because...? Pbarnes 06:39, 15 February 2007 (UTC)
Er... undue weight and the promotion of the religious views of a noisy group of individuals pushing pseudoscience nonsense. Vsmith 11:44, 15 February 2007 (UTC)

Merge, if my above wasn't clear. Adam Cuerden talk 10:44, 15 February 2007 (UTC)

Keep It's useful information for this article. Pbarnes 23:15, 16 February 2007 (UTC)

Delete, obviously - it's been AfD'd, it's failed DRV, it doesn't belong here. Guettarda 01:47, 17 February 2007 (UTC)

This may seem mean, but you sound like a bitter old man in ever comment I have ever read from you. Pbarnes 02:35, 17 February 2007 (UTC)
Bitter? Nope. Just extremely frustrates with your total contempt for your fellow editors. You have been nothing but rude and dishonest from the start. Despite community consensus that this material was unsuitable for Wikipedia you have re-created the material at least half a dozen times and re-inserted it in here. Guettarda 02:49, 17 February 2007 (UTC)
Please, explain how the information provided in the section is "unsuitable for Wikipedia". Pbarnes 03:03, 17 February 2007 (UTC)
As you know, having participated in the deletion debates, if something fails AfD, it is because it is unsuitable for Wikipedia. If it is to be reused somewhere else, then it is closed as a merge. The consensus was to delete these articles. You re-created them repeatedly, which shows contempt for the opinion of the community and Wikipedia policy. Now you have re-inserted the material here. You can't circumvent an AfD by sticking the material in another article. Guettarda 03:52, 17 February 2007 (UTC)
I believe it failed because of non-notability. According to wikipedia, information which does not warrant it's own article can and should be included in other, broader, articles. The section on the common descent article is hardly non-notable. Pbarnes 04:08, 17 February 2007 (UTC)

Keep - Sections such as this make the article more inclusive of all information on the topic rather than just summarizing information that is in other articles, such as evidence of evolution or artificial selection. Bubbamagic87 02:41, 17 February 2007 (UTC)

Mergeor Delete. It has nothing to do with this article, which is about the science of common decent. Either put it in an appropiately religiously based article or delete. --Michael Johnson 14:10, 17 February 2007 (UTC)

Mergeor Delete. Completely agree with Michael Johnson: it has no place in an article about science. --RE 17:58, 17 February 2007 (UTC)

"A POV fork is a content fork deliberately created to avoid neutral point of view guidelines, often to avoid or highlight negative or positive viewpoints or facts. Both content forks and POV forks are undesirable on Wikipedia, as they avoid consensus building and violate one of our most important policies." Wikipedia:Content_forking Pbarnes 20:22, 17 February 2007 (UTC)
With respect, what has that got to do with this? --Michael Johnson 01:12, 18 February 2007 (UTC)
It is content forking to separate a religious section about common descent from the scientific sections unless there are legitimate reasons for doing so, such as keeping the article on evolution from being too long for wikipedia's standards, therefore the article was made to be strictly scientific. This article on common descent is hardly too large for this information. Pbarnes 07:00, 18 February 2007 (UTC)
Science and Religion are very different subjects, so forking hardly applies. --Michael Johnson 08:05, 18 February 2007 (UTC)

Keep but make it shorter. rossnixon 00:59, 18 February 2007 (UTC)

[edit] Formatting

Should "examples of common descent" come before "evidence of universal common descent"?

One editors feels it shouldn't because of importance and triviality...both reasons are subjective in relation to this topic. I feel it should remain as suggested because when explaining theories, one always starts with the observable facts which are fundamental to the theory when available and then builds from those using other evidence to suggest something much broader. Common descent is PROVEN because it has been observed. That is the best evidence we have for universal common descent and this is why it should be at the top of the article. Pbarnes 00:54, 13 February 2007 (UTC)

The "one editor" is me. This section describes several examples of high variability among individuals who share a late common ancestor. It is not about "examples of common descent" (whatever that may mean), it is about "examples of variation among individuals sharing common descent in the last few millenia". As I wrote above, "common descent", unless otherwise specified, almost always refers to what you insist on calling "universal common descent". Therefore, "Evidence for common descent" (i.e. your "universal" common descent) should come first (both in importance and in order), before "examples of high variability among individuals sharing a late last common ancestor" (which is what the disputed section really is). Hopefully this discussion will help make the overall article clearer on this point. --Thomas Arelatensis 11:47, 13 February 2007 (UTC)

My argument has nothing to do with a seperate definition of "common descent" and "universal common descent". Maybe I wasn't clear enough in my previous comment. The best evidence we have for "individuals sharing a late last common ancestor" is the fact that we have observable proof that there are "individuals sharing common descent". Darwin didn't have all this DNA/fossil information you so insistently want to make most important, yet he still was able to provide a solid argument on the best evidence around...and that is examples which demonstrate the theory. I think "examples of common descent" should come before "evidence of universal common descent". Pbarnes 17:37, 13 February 2007 (UTC)
I'd have said the best evidence was the Universal Genetic Code, and the fact that everything arranges into trees with high consistancy, no matter what test you use. Adam Cuerden talk 11:52, 15 February 2007 (UTC)
Yes. This article is about common descent, not universal common descent. "Examples of common descent" should not only come come before "Evidence of universal common descent," but the later needs to be omitted completely. Read my comments in the first two talk sections above. This split confuses the subject. Universal common descent leads into talk about Universal Common Ancestor (UCA) Last Universal Common Ancestor (LUCA) or Last Common Ancesor (LCA), and these are unrelated topics that deal with origins of life. They should not even be mentioned here, except for external links. Furthermore, as stated above and elsewhere numerous times, at the single cell microbial level, at the deepest branchings of any phylogenetic analyses, there never was a last universal common ancestor because of the enormous amount of lateral gene transfer taking place between genomes, gene transfer, and genome fusions. Wiki is at the forefront of scientific knowledge and how we offer and present it to the world. This article does not pass and needs major category reworking. Any reference to LUCAs and LCAs belongs in those articles and phylogenetic trees belong in the phylogeny and evolution articles. Valich 02:05, 20 March 2007 (UTC)


[edit] English is a nice language...

...when used correctly. This is horrendous:
"In biology, a group of organisms is said to have common descent if they have a common ancestor. The most recent common ancestor is the most recent individual or population which is an ancestor of all of the species being referenced. The theory of universal common descent proposes that all organisms on Earth are descended from a common ancestor or ancestral gene pool.[1] It is the accepted theory for the origin of modern biological species among biologists."
The rest of the article is pretty much just as bad. •Jim62sch• 22:37, 16 February 2007 (UTC)

The purpose of talk pages is to work on improving articles, not merely to complain about them. Please suggest an alternate phrasing -- or better yet, just change it in the article. --FOo 04:40, 18 February 2007 (UTC)

Oh, is that the purpose of talk pages? I did not create the mess, nor do I have the time to fix it. Realistically, the article requires a complete rewrite, and I much prefer to edit good prose not to do a rewrite of substandard prose. •Jim62sch• 20:45, 19 February 2007 (UTC)

[edit] Reducing fringe theory section - Again!

Pbarnes, this is getting out of hand. The above discussion shows a clear consensus to (at the very least) reduce the "fringe theory" section. I counted 8 against 2 to either merge or keep the current, "shorter" version of the section. You are deliberately ignoring this clear consensus and trying to impose your own, isolated view on the matter. Fringe theories should get a short mention and a link to related articles (e.g. baraminology), perhaps a few (purely bibliographic) references, certainly not several lines of quotations! Detailed exposition of fringe viewpoints does not belong in this article.

In short: Please stop extending the section, except perhaps for providing concise, quote-less references. Thank you. --Thomas Arelatensis 13:07, 19 February 2007 (UTC)

[edit] Format

Logically it makes far more sense to move from generalities to specifics - thus, specific examples should go after general explanations. Guettarda 18:53, 19 February 2007 (UTC)

This has already been discussed. You can add you opinions if you want and maybe we can get some kind of consesus. Talk:Common_descent#Formatting - Pbarnes 19:12, 19 February 2007 (UTC)

Hmm... seems that consensus is here. I see only one editor versus four. That one editor has been quite persistently reverting, but against consensus. Vsmith 20:27, 19 February 2007 (UTC)

[edit] Brassica

The note says that Raven et al. said: "all produced from a single specie of plant". Is this a misquote, or a typo on their part? Guettarda 20:42, 19 February 2007 (UTC)

I fail to see anything wrong with it. Pbarnes 06:53, 24 February 2007 (UTC)
Er...specie? Guettarda 07:11, 24 February 2007 (UTC)
You see that in old texts, sometimes; I believe it was more accepted in the past than it is now. Adam Cuerden talk 12:34, 24 February 2007 (UTC)
But this is a quote from a 2005 textbook. Guettarda 16:14, 24 February 2007 (UTC)
I received this quote from an email conversation from my botany professor. I will talk to her about it on Tuesday. Pbarnes 02:03, 26 February 2007 (UTC)

[edit] "Observed examples of common descent"

What the heck does that mean anyway? Guettarda 20:45, 19 February 2007 (UTC)

"The purpose of talk pages is to work on improving articles, not merely to complain about them."  :) •Jim62sch• 20:54, 19 February 2007 (UTC)
My apologies. Let me rephrase my question - can someone please explain to me what the heck that is supposed to mean, so that I can try to change it into something that belongs in the article? Guettarda 21:16, 19 February 2007 (UTC)
I think it's supposed to mean "examples of speciation" - one could well argue how relevant the section is. Adam Cuerden talk 21:23, 19 February 2007 (UTC)
It might be relevant -- we can discuss that. But it is poorly written, unless our aim is to appeal to 4th graders. •Jim62sch• 21:31, 19 February 2007 (UTC)
It's not entirely irrelevant, but it needs an introduction setting out that speciation is the process by which UCD works, and seems far too long for a minor point (in terms of UCD). Better examples, including transitional forms like Ambulocetus, Tiktaalik, Archaeopterix, etc, would make the section more on-point.
We could also consider adding more evidences: vestigal forms - the limbs in snake embryos, the appendix in humans, etc. I'm not aware of a better summary of the evidence than this one, and, while we need not use its examples, I'd suggest that we try and cover all its major categories. Adam Cuerden talk 21:35, 19 February 2007 (UTC)
I think the haplochromine species flock would be a great example, although so is Brassica oleracea. Sadly, AFAICT, the mechanisms of differentiation in B. oleracea haven't been studied in detail (presumably it's a hox-type mechanism). Guettarda 21:47, 19 February 2007 (UTC)
OK, so how about a change of the section title to "Examples of Speciation", followed by an intro, followed Guettarda's examples (and maybe another). •Jim62sch• 21:58, 19 February 2007 (UTC)
Let's go for it, though we really need an opening paragraph. I'll try and help out in the morning. Adam Cuerden talk 22:45, 19 February 2007 (UTC)
I think the purpose of this section was to give examples of "observed" speciation that generated a large amount of variation. The idea is that even readers unfamiliar with (or hostile to) scientific evidence for UCD are bound to accept that dogs or brassicae do share a late common ancestor, and therefore that such a process can indeed generate enormous diversity. Of course AFAIK nobody "observed" the speciation of finches, so I don't know what they're doing here.--Thomas Arelatensis 13:37, 20 February 2007 (UTC)

[edit] Phylogenetic trees

I've rewritten this section completely - it was totally off-topic, talking about one single confounding factor for some molecular trees exclusively, explicitly excluding morphological trees, and ignoring completely the evidence provided by either type Adam Cuerden talk 20:55, 19 February 2007 (UTC)

A large improvement over the original. I edited a bit for clarity. •Jim62sch• 21:17, 19 February 2007 (UTC)
Nice work! Adam Cuerden talk 21:18, 19 February 2007 (UTC)
Read my comments above in the first two talk sections. This artilce is not about phylogenetic trees and this subject should not even be introduced here. Phylogenetic trees show taxonimic groupings, evolutionary branchings and evolutionary descent but are not about common descent. Phylogenetic trees do not show common ancestors. Unlike cladograms, phylogentic trees do not have nodes that represent common ancestors. This is not what the base of the branches represent. Yes, it is a very well-wriiten section, but it belongs in evolution, not here. By contrast, cladistics shows derived characteristic traits from common ancestories represented by nodes and at the base of cladogram is a common ancestor. The reason why there are so many dissimilar phylogenetic tees is because of the disagreement about the chronology and the taxonomic groupings of evolutionary branchings, not common descent.Valich 02:05, 20 March 2007 (UTC)

[edit] Creationism and common descent

Can we lose this section? This isn't a long article, and to give space to a fringe creationist belief seems excessive. This just doesn't seem the place. Adam Cuerden talk 20:00, 23 February 2007 (UTC)

Yes, of course. Guettarda 21:31, 26 February 2007 (UTC)
Fully supportive - thanks, Vsmith 12:24, 27 February 2007 (UTC)

[edit] New Section?

What about a section on "Difficulties for universal common descent" dealing with Horizontal gene transfer, hybridisation between species, the fusion origin of eukaryotes, etc? Basically, all the muddling factors that make it difficult to interpret. Adam Cuerden talk 11:39, 19 March 2007 (UTC)

Well, they're not really "difficulties" in that they don't weaken the theory. Whether the LCA was an individual or a bunch of gene-swapping individuals does not fundamentally alter the picture of universal common descent. However, I agree that we should discuss these things, and the fact that the Tree of Life is more like a mangrove than like a single-root tree.--Thomas Arelatensis 14:40, 19 March 2007 (UTC)
True, I agree my title is unfortunate, but I just think that eight or so words isn't enough to go from the simple, tree-view that's relatively easy to understand to the complex HGT-added view.
It's probably useful to explain the simple view first - e.g. the article much as now - then start adding, in a new section, fusion events, HGT, and all those fun things that take the simple view and add on new relationships.
Because the key thing to remember is that the simple view may not be 100% accurate, but neither is it 100% wrong: speciation does happen, and things (mostly) split off and diverge, and stay (largely) unconnected with distant branches. A lot of the edits to add HGT in are being donein such a way that the simple view - which incorporates every other important concept except HGT and similar - is being lost. I don't think it does anyone a favour if they understand HGT and not speciation, or, worse, misread the explanation of a small initial population, disregard "gene-swapping" as they don't understand it, and think science supports Baraminology and created kinds - those creationist "every family-level group of species (except Hominidae - we ain't related to no monkeys - evolved from a single pair of animals on Noah's ark.
I think getting this right means explaining HGT, fusion, and the other fun stuff last, after a strong grasp of the basics is there. Adam Cuerden talk 02:15, 20 March 2007 (UTC)

[edit] Common Descent Breaks Down at the Single Cell Level

As stated under microorganisms, "Microbes freely exchange genes by conjugation, transformation and transduction between widely-divergent species. This horizontal gene transfer, coupled with a high mutation rate and many other means of genetic variation, allows microorganisms to swiftly evolve (via natural selection) to survive in new environments and respond to environmental stresses. This rapid evolution" did not involve a common ancestor or LUCA. Mentioning links to unicellular organisms, microbes and viruses, that did not have an LUCA, greatly expands this article with enrichening, progressive and factual content not found elsewhere, and this leads the reader to a greater, more realistic, understanding of life, how it came about, and how it works.Valich 01:16, 28 March 2007 (UTC)

[edit] How does single cell "evolve" to multi-cellular differentiated structures?

Evolution holds that individuals do not evolve, but species do evolve.

You have on your microscope plate a single cell. It reproduces by fission: splitting into two. Obviously, since it does not have sexual organs and look around for a cell of the opposite sexual configuration (gender).

In order to make the transition, the cells must start to stick together instead of separating to go their own ways. They must be able to continue to reproduce into two separate organisms each made of groups of cells instead of single cells, until their sexual organs become functional. Put simply, it just does not seem possible for a multi-cellular, diffentiated-cell organism, whose sexual reproductive organs have not quite yet "evolved" to a functional condition, to be able to reproduce (i.e. avoid extinction) by splitting into two neat copies (which may be the first to have the genetic evolutionary step of being sexually fertile) of the original... and be the same gender!

To me, this, and the many missing transitional life forms that have not been found in the record, is why evolution is only a theory. Nobody was there 3.9 billion years ago who's alive today and say, "yep, that's what I saw over the last 3.9 billion years of my life". GBC 22:30, 5 September 2007 (UTC)

This talk page is for the discussion of improvements to the article. It is not a forum for debates or for argument from personal incredulity. However, we do have articles on colony organisms and the evolution of sex. --FOo 02:51, 6 September 2007 (UTC)
There are many organisms that are "intermediate" between single-cell and multi-cell, it's just that you don't know about them (Volvox is fun, but sponges are more interesting because they have close single-cell relatives). Also, you seem to be confused about sex, which (believe it or not) does not require sexual organs. All that is required is the capacity to fuse genetic material between cells, and even asexual organisms do that routinely (see plasmids). Yeasts can undergo sexual reproduction; could you tell me what is the "sexual organ" of a yeast cell ? ;) --Thomas Arelatensis 09:51, 12 October 2007 (UTC)

[edit] Cenancestor?

I was going to start up an article on "cenancestor", but would it be better if the term pointed to this article? And, is "cenancestor" still commonly used in the literature? StevePrutz (talk) 05:19, 19 May 2008 (UTC)

I created a redirect in the meantime. StevePrutz (talk) 22:43, 21 May 2008 (UTC)