Talk:Last Common Ancestor

Previous discussion

As for the cartoon, it was reinstated. It appropriately makes the point defined later in the text, ie., "...the LCA is the seminal individual that first coded the mutation..." That would be mom or dad, no way around it. I cannot believe someone would have a problem with that illustration in Wikipedia! And if he did this discussion page is the place to make the case, not with some hit and run on the article. Tom Schmal 02:48, 15 August 2007 (UTC) _____________________________________

Do not see much value for the reader in merging LCA and MRCA.

MRCA: "It is incorrect to assume that the MRCA passed all (or indeed any) of his genes down..." Contrast this concept to that of the LCA: "Every person on earth owes 100% of his genes to the LCA."

How is that possible without us being clones of the LCA? 207.189.230.42 (talk) 09:05, 24 July 2008 (UTC)

MRCA: "The existence of an MRCA does not imply existence of a first couple..." Contrast this to implication of the LCA, which is: "the LCA is seminal individual that first defined the new species."

First you would have to define what crucial characteristic suddenly makes an offspring the first member of a new species, and not a member of its parent(s) species. Is that even tenable? 207.189.230.42 (talk) 09:05, 24 July 2008 (UTC)

One entry speaks to lineage and the other to evolution. Yes, both pages have something to do with heritage, as atoms and molecules have someting to do with matter, but it would be a stretch to say they should be defined together - especially given the different core meanings as seen above.

For the interested reader, the entries each have the other's links, which is appropriate. Tom Schmal 00:14, 24 July 2007 (UTC) _____________________________

And let me add that someone's sticking "MRCA" where it originally said "LCA" does not make the two terms identical! It was changed to read: "Proponents of the Multiregional hypothesis would place the "MRCA" of humankind two million years ago..." Which is ludricous, because the MRCA according to the entry itself is two thousand years old, not two million! jeez! Tom Schmal 00:26, 24 July 2007 (UTC)

Confusing article

This article is extremely confusing. It keeps flipping back and forth between defining the LCA as the species founder and as the most 'recent' common ancestor. These are two completely different concepts. If the article is not cleaned up, I am considering removing links to it from pages such as Mitochondrial Eve‎. See examples below. Fred Hsu 02:41, 2 November 2007 (UTC)

Last Common Ancestor (LCA) is the most recent common ancestor of two populations that came to be separated by a species barrier.

OK, so the above defines LCA as the most recent (closer to present time) organism which is an ancestor of at least two populations (or species or organisms).

Along the hominid line there have been many branches, leading for example, to Australopithecus africanus, Homo erectus and Homo neanderthalensis. Although every species has an LCA, recent discussion is...

A species does have a LCA; it is the MRCA of all living members of the species. This LCA is NOT the individual at the bifurcation point between two species (say between Neanderthals and other hominid species); that individual would be the LCA of Neanderthal and another hominid species.

Proponents of the Multiregional hypothesis would place the LCA of humankind two million years ago as an early form of Homo erectus

You mean the MRCA of living people today lived 2,000,000 years ago? See below.

Computer simulations suggest that every person living today could share a common ancestor who lived as few as 2,000 years ago

So the MRCA of living people today lived 2,000 years ago?

Sigh. Fred Hsu 02:41, 2 November 2007 (UTC)

_______________________________________

Thanks for coming to a discussion page Fred. Probably I could have done better keeping LCA and MRCA straight.

An LCA is in fact the individual (or founding group) at the bifurcation point between two species. For us, this individual, which lived between two million and 40,000 bce, and no others contributed ALL of the genes that make up humanity. If we could pin the date down more closely we could probably call it "The MRCA between modern man and XXX" but we don't know the XXX.

Now fast forward to 2007. You and I and every person on earth could trace our ancestries back to around 2,000 years ago and find a common grandparent, aka The MRCA of All Mankind. Unlike the LCA, the genetic contribution of this ancestor to any one person is extremely small. This is because some ten million of his contemporaries ultimately get into the action.

Obviously the MRCA of All Mankind cannot be both of these individuals. Chang, et al, call the individual of 2,000 years ago the MRCA of All Mankind. So we call the other guy, the individual that began the species, the LCA (of all mankind).

Tom Schmal 05:59, 6 November 2007 (UTC)

Are you sure 'LCA of mankind' is defined in the academic circle in the way you define it? Without an additional XXX species to define two groups, LCA of mankind will automatically fall back to MRCA of mankind. How can you ever define LCA at a bifurcation point without at least two parties? This is the source of the confusion. Fred Hsu 13:05, 6 November 2007 (UTC)

To describe the bifurcation point, “MRCA" and "LCA" of Chimps and Humans, for example, are interchangeable. However you can't use the former term when you want to describe this individual as the seminal parent of one of the branches, eg, the humans, because is already taken. It’s Chang’s guy, the MRCA of all Mankind, who lived a few thousand years ago. So instead you use the LCA of all Mankind. This one name allows for both descriptions - as the bifurcation point and also as the parent of the species. That is why it is better to call him the LCA.

I am hopeful the X of the LCA of Mankind and species X will be clarified in the pretty near future, perhaps when the two parties sponsoring the two theories kiss and make up.

In the future Concestor may replace LCA but it is pretty new and for now all the literature is LCA.

This has really been an excellent exchange. I think the article's “Other Common Ancestor Titles” section, and maybe more – or maybe the MRCA article - could be clarified now. If no one takes a shot at it after a while, I will. Tom Schmal 17:09, 6 November 2007 (UTC)

The article states "Unlike the LCA, the genetic contribution of this ancestor (MRCA of humankind) to any one person is extremely small". Are you saying that LCA (as defined in one way in the article to have lived at 2,000,000 years ago) contributed even more significantly than MRCA at 2,000 years ago to human kind? The longer we go back the more contribution? How about the first bacteria? The LCA (as you define it) became ancestor to all humans and some unidentified XXX species. Are you saying that this LCA contributed more to both humans and XXX than human MRCA and XXX MRCA to each of their descendant groups?

This article looks more and more like a term seized by someone to explain an idea which the term does not originally represent. The article states, "Chang, et al, call the individual of 2,000 years ago the MRCA of All Mankind. So we call the other guy, the individual that began the species, the LCA (of all mankind)." Where is the source for this? I will check your sources and do research of my own. But it appears that you have arbitrarily chosen to use this term for your own purpose.

What exactly does 'last' in LCA mean? Does it mean 'last' in the sense that the 'last meal' I ate is later in time than the 'previous meal' I ate? If this is the case, the LCA means exactly the same thing as 'most recent' comment ancestor; they are really interchangeable. And you can't say that LCA of all humankind lived 2,000,000 years ago while MRCA of all humankind lived 2,000 years ago.

If by 'last' you mean the last ancestor you find by tracing ancestry backward starting at present time, then you can probably say, the individual who lived 2,000,000 years ago was the 'last' common ancestor' of all humankind who was NOT an ancestor of some other species XXX. You need to explicitly list two species in order to use this term, then. You can't just say the 'last common ancestor' of all humankind, because this organism is the first self-replicating RNA. You've got to stop tracing ancestry somewhere. If you don't identify a species to stop the back tracing, LCA of all any species will always be the first self-replicating RNA. Besides, I AM NOT SURE THE ACADEMIC CIRCLE ACTUALLY USES 'LCA' IN THIS SENSE. See the now-deleted 'most ancient common ancestor' article which I managed to delete via AfD; that articled attempted to invent a concept like this without any academic support. Fred Hsu 23:19, 6 November 2007 (UTC)

OK. I checked all references listed on the article, except the two books by Klein and Leakey respectively (I don't have these books). Not a single reference paper mentions LCA. They all talk about MRCA. Continue to look elsewhere online. Fred Hsu 23:45, 6 November 2007 (UTC)

Possible references for LCA

Here are some web pages I am looking at now. Unfortunately, some of these only show abstract. Fred Hsu 01:27, 7 November 2007 (UTC)

Papers

• About the last common ancestor, the universal life-tree and lateral gene transfer
• Modern African Ape Populations as Genetic and Demographic Models of the Last Common Ancestor of Humans, Chimpanzees, and Gorillas
• Recent African Origin of Modern Humans Revealed by Complete Sequences of Hominoid Mitochondrial DNAs
• Estimating the age of the last common ancestor of extant primates using the fossil record

Abstract

• The Last Common Ancestor: What's in a name?

It is clear from all papers that LCA is exactly MRCA. Not one paper uses LCA of group ABC to mean the individual at the bifurcation point of group ABC with some other unspecified group XYZ. In all cases I found, all occurances of LCA can be replaced by MRCA without altering the meaning of the paper. In a few instances, unqualified LCA (that is not LCA of something; simply LCA) is used to identify the last universal common ancestor, which makes perfect sense. Unqualified LCA is the LCA of all living organisms.

If you are not satified, try searching at Blackwell Synergy or google scholar.

I am going to:

• remove incorrect information from the LCA article (e.g. "the LCA is the seminal individual that first coded the mutation that created the characteristic that defined the new species", "Although every species has an LCA, recent discussion is", and "Proponents of the Multiregional hypothesis would place the LCA of humankind two million years ago")
• remove redundant discussion on Multiregional hypothesis and dates; these have their own pages and are tangential to MRCA and LCA.
• Add references I found to the article. Remove all existing references (except the two inline references) as they are irrelevant to LCA.
• add a template to recommend that this article be merged into MRCA. The MRCA article already covers everything that LCA should cover. Since LCA is just another name for concestor (which is also covered in MRCA), it does not make sense to have a separate article for LCA.

Thanks. Fred Hsu 03:58, 7 November 2007 (UTC)

DONE. Fred Hsu 04:34, 7 November 2007 (UTC)

Removed content

I am removing the following content. For sake of fairness, I move them here. If anyone can find real references for these, feel free to move them back to the article, with proper inline citations. Fred Hsu 04:11, 7 November 2007 (UTC)

lead section

LCA of Humankind

(this complete section is wrong - as per research done as indicated in previous section on talk page)

The most famous LCA is the so-called “Missing Link”, the most recent common ancestor of the genera Pan and Homo, that is, of chimpanzees and humans.

Along the hominid line there have been many branches, leading for example, to Australopithecus africanus, Homo erectus and Homo neanderthalensis. Although every species has an LCA, recent discussion is often in reference to the branching of modern man from archaic Homo sapiens (now extinct).

Proponents of the Multiregional hypothesis would place the LCA of humankind two million years ago as an early form of Homo erectus. A larger consensus of opinion, however, is that the last common ancestor of all mankind was born much more recently, probably in Africa, between 100,000 and 40,000 years ago. Its descendants spread across the earth from there, replacing all other forms of hominid.

LCA of two species

(again, this is completely wrong)

While the new species will owe all its genes to its LCA, the LCA itself will be a member of the original line, not the new one. Its genetic contribution to that original line may be de minimis but as a convention the term LCA is often used as if it were the ancestor of both species.

LCA: a single organism?

‎At its most narrow definition, the LCA is the seminal individual that first coded the mutation that created the characteristic that defined the new species (see illustration). However, the defining mutation may be subtle and initially not a speciation event. In sexually-reproducing organisms, until the new species establishes itself there are going to be some, possibly many, generations of gene-swapping back to the parent branch.

Genetic evidence points to a long, perhaps a million year period before separation of the Pan and hominid lines was complete (see Patterson reference). Conversely, some experts believe that as recently as 40,000 years ago a non-anatomical trait, such as improved speech, suddenly emerged in archaic Homo sapiens (see Leakey reference). The individual first passing on this mutation would be the LCA of fully modern man.

Depending on the process that gives rise to the species, the LCA can sometimes be better described as the initial small breeding group or clan or founding population, all members of which carry a common species-defining mutation.

The Drosophila experiment conducted by Diane Dodd. Here, the LCAs may be best described as founding populations.

Other common ancestor titles

...It should be recognized, however, that every common structure in living people — from the makings of our mitochondria to our hair follicles — has an “Eve” that lived somewhere in the great distance between the LUA of three-plus billion years ago and the Last Common Ancestor of possibly 40,000 years ago. (what is this talking about?)

While each of us may have inherited genes from the MRCA of All Mankind, we have also inherited the genes from millions of his contemporaries. This case is different from that of the LCA, to whom every person on earth owes 100% of his genes, and to no other. (what?)

References

• Chang JT (1999) "Recent common ancestors of all present-day individuals". Advances in Applied Probability 31: 1002-1026.
• Origins of Modern Humans: Multiregional or Out of Africa?, by Donald Johanson.
• N. Patterson et al. "Genetic evidence for complex speciation of humans and chimpanzees"; "Genetic evidence for complex speciation of humans and chimpanzees"
• Douglas L. T. Rohde, Massachusetts Institute of Technology November 11, 2003 "On the Common Ancestors of All Living Humans"
• BBC Science & Nature: "The Day we learned to think". Citation "Anatomically modern humans (Homo sapiens) emerged in Africa roughly 100,000 years ago." This would not necessarily be the LCA, which could be more recent if defined by a non-anatomical trait.
• Richard Klein, “The Human Career,” and Richard Leakey, “People of the Lake.” suggest a recent (40,000 yrs) LCA, coincident with the emergence of Cro-Magnon culture (Leakey).

(done) Fred Hsu 04:34, 7 November 2007 (UTC)

Article should be restored for discussion

Mr. Hsu, you have just gone too far. Chopping up this article on the strength of your own personal misunderstanding of it is not right. I am obviously not a wiz at manipulating the Wikipedia but from what I have read here about how differences of opinion should be handled I can say absolutely that your sudden attack is not at all in the spirit of what we are trying to build.

This article made the Wikiedia better, your removing it made the Wikipdia worse.

You say you are proposing a "Merge" of this article with another one, one that you yourself have heavily edited. You ask for discussion but all that you left for this discussion is dismembered. Why did you do that? And you did it he day after I responded to you! What was the rush?

I have tried to explain to you the difference between the LCA of Mankind and the MRCA of Mankind and have obviously failed - but we and others can discuss the science later. What is needed now is that you reassemble the article to the way it was somewhere around November 5th. That way the evidence will be available in continunity and the issues, if any, can be addressed by interested parties and experts. Perhaps all it needs is more clarity around your issue and it will be fine.

So would you do that please? And <smile> don't forget the cartoon Tom Schmal 04:42, 16 November 2007 (UTC)

The revision before I started to clean up can be accessed here. Your explanation of 'your view' on LCA was expressed on the article itself. It was very confusing, as I discussed earlier on this talk page. So, I had to dive into the actual references, all references you have listed on the article. Absolutely NONE supported your theory, as I also explained on this talk page later.

Wikipedia tries to be neutral, by presenting all sides WITH ACTUAL SCHOLARLY REFERENCES, not just whims. Please check out the URLs I provided earlier on the 'most ancient common ancestor' article which I managed to delete via AfD (Article for Deletion). Your personal theories do not count as a 'side'. If you can provide references to back up your second definition of LCA, of course we will be happy to have it on wikipedia. I beg you to actually read what I wrote on this talk page.

I beg you to read what I wrote on this talk page carefully. I started with questions. Then I listed confusing points. Then I follow up on your references. I understood your references. I concluded that none supported your theory. All papers used LCA interchangeably with MRCA. So I delete all incorrect paragraphs from the article. All steps are faithfully laid out on this talk page. I even included deleted content here for future refrences. What more do you ask of me? Fred Hsu 06:00, 16 November 2007 (UTC)

Thank you for putting the page back together again. Maybe the key to unconfusing you is to demonstrate the the difference in the two ancestors with an example.

As a first step, without going into other issues, can you see that the same name cannot be used for the two persons in this chart? They are separated by thousands, maybe millions of years. Tom Schmal (talk) 19:00, 19 November 2007 (UTC)

I understood your point since my first comment on this talk page. Please check what I wrote. You do not understand what I have been trying to tell you. Please re-read what I wrote on this talk page. Your definition of LCA has NO backing from any paper. Please tell me which book or paper gave you this idea about this particular definition of LCA. If you cannot cite a paper or a book, your ideas are NOT fit for wikipedia. Wikipedia is not a soapbox. Fred Hsu (talk) 01:40, 20 November 2007 (UTC)

From your first comment to me you state that my LCA and your MRCA of All Living Humans should be the same. For example, you state: "A species does have a LCA; it is the MRCA of all living members of the species." Later you state: "You can't say that LCA of all humankind lived 2,000,000 years ago while MRCA of all humankind lived 2,000 years ago." Yet this is exactly what I am saying! Look again at my chart. You tell me, what is the correct name for the individual on it, the founder of the species, entitled "LCA of all living humans?" I await your response.

Yes you have back-up issues such as non neutral PoV, lack of references, making up the term "LCA" and etc. We can discuss those in due course. I think the best way to move forward is for you to state that you either agree or disagree that the two individuals on my chart - whatever their names - must be different and *can not* have the same name. Do you agree or do you disagree? How can we move forward unless you clearly state your position? —Preceding unsigned comment added by Tom Schmal (talk • contribs) 03:37, 20 November 2007 (UTC)

Tom, I am afraid you completely miss my point. I know the concept you are trying to convey. But its name IS NOT Last Common Ancestor. Perhaps there are other names you can find from papers and books. But until you find them, your theory is not worthy of a place in wikipedia. Please see Wikipedia:No original research. "LCA" is used by researchers to mean exactly MRCA. See real references I added to the article. You cannot hijack a phrase used by researchers to mean something completely different that you cook up.

I beg you, read my previous words on this talk page. Pay special attention to the 'most ancient common ancestor' article which I managed to delete via the deletion process. Please click on the URL in the following quote to see for yourself. I understand your idea; it's exactly like what Robert tried to present in the now-defunct 'most ancient common ancestor'. Fred Hsu (talk) 05:28, 20 November 2007 (UTC)

See the now-deleted 'most ancient common ancestor' article which I managed to delete via AfD; that articled attempted to invent a concept like this without any academic support.

You say you "know" the concept - but can't state whether you agree or disagree with the it? Fred, this is not new stuff. We must have two individuals here, not one (please review the chart), do you agree or don't you? Tom Schmal (talk) 15:12, 20 November 2007 (UTC)

You are trying to sidetrack the issue here. If I say I agree that there is a individual who first had some sort of mutation, you will simply take my answer and spin it as if I agreed to your interpretation of LCA. For the record, I disagree with your interpretation of LCA.

Now, answer my question. I will repeat it here to save you time. Where did you read about this definition of LCA that you use to mark your 'seminal' individual? Please, give me a straightforward answer. Did you read about it, or did you just seize LCA and use it to mean what you believe needs to be named?

If you did not read it on a paper or a book, then please stop arguing. Fred Hsu (talk) 00:50, 21 November 2007 (UTC)

LOL, okay I will take that for a "Yes" you agree there is a seminal individual (or founding population) that cannot be or be called the MRCA of All Mankind - that name already being taken by your very own article. As for sources for the name of this fellow, there are lots - but you don't have to look any further than your own reference, the very one you put in the article! It is a good one!

"Recent African Origin of Modern Humans Revealed by Complete Sequences of Hominoid Mitochondrial DNAs" Here are some findings by these esteemed scientists:

"The main controversy, therefore, has centered around the estimated age of the LCA and the reliability of the mitochondral clock on which it is based... the upper 95% confidence limit of the age of the LCA is as low as 179,000 years.

"While such an estimated age of the LCA by no means implies that modern humans emerged at that time, the age expected according to the mltitregional hypothesis should be as old as 1 Myr if gene exchanges among local populations were limited... A more likely explanation is that the age of the LCA indicates that modern humans originated much less than 1 Myr ago without integrating the substantial diverged H. erectus genes."

What say you, my friend? Ready to smoke the peace pipe? Tom Schmal (talk) 01:54, 21 November 2007 (UTC)

______________________

You were confused, maybe others were also. However, you have shed some good light on how to present the article. The First Definition of LCA was originally "The parent of a new species." Another contributor changed that to "The MRCA of two populations." This I believe led to the the confusion. So my plan from here is to restore a "parent" type idea as the First Definition and the bifrucation definition (which, as you point out, it shares with MRCA) as a secondary. Hopefully that will resolve the issue Tom Schmal (talk) 14:49, 21 November 2007 (UTC)

Tom, do you really understand this paper? It does not use LCA the way you use it. You look at the number of years and automatically assume they are talking about the same 'seminal individual' as in your mind. From your reply, I conclude that you invented the meaning of this term and that you have no source to cite.

I replaced the reference with the same paper in PDF format, so you can read the whole article. Please read it and tell me where it uses LCA to mean the individual at a bifurcation point of human and some unknown XYZ humanoid species. For your edification, I'll try to summarize the paper for you. The paper selects among a dozen humans 3 people: one European, one Japanese and one African. They then use mtDNA of apes and these 3 people to try to estimate the LCA of all human kind, that is, the most recent common ancestor of these 3 people, in the hope that this MRCA estimate is representative of that of MRCA of all humankind. The fact that the paper comes up with a wildly different (farther in the past) time estimate for MRCA compared to the 3,000 years ago estimate of Chang, et al is tangential to our discussion here. These researchers are trying to disprove multiregional hypothesis. The differences in time estimate between Chang and them is relatively small, if you compare both numbers of the supposedly >1 million year estimate for LCA if multiregional hypothesis were true.

Pay attention to the abstract and to the phylogenetic trees on page 535. Compare the 4.9 million year estimate for common ancestor between human and chimps to 143,000-18,000 years for LCA amongst all humans. Then look at the phylogenetic trees on page 535. See how the bifurcation (branching) point into humans and chimps represents the last common ancestor of all humand and chimp? See how the most recent branching point into all three humans represents LCA of all humankind. Please point out where your idea of the 'seminal' individual is on these trees. Fred Hsu (talk) 01:55, 22 November 2007 (UTC)

I looked and I understood. Now you look Fred - look at the title: "Origin of Modern Humans." This paper calls it the LCA. Get it? Origin = LCA. It just doesn't get any plainer than that. Tom Schmal (talk) 14:43, 25 November 2007 (UTC)

The term LCA is ubiquitous, what do you mean "invented" the usage?

http://www.itee.uq.edu.au/~listarch/fod/archive/2006/05/msg00003.html Prof Bernard Degnan, University of Queensland Any meaningful reconstruction of the last common ancestor (LCA) to all living metazoans through comparative analyses of extant taxa requires input from the most ancient body plans

http://www.sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2006/11/16/MNGMFMDVG31.DTL&type=printable According to their DNA analysis, the last common ancestor of Neanderthals and humans lived about 700,000 years ago, and the ancestral populations of humans and Neanderthals diverged and split into distinct species about 370,000 years ago -- well before the evolution of anatomically modern humans

http://www.palaeos.com/Vertebrates/Lists/Glossary/GlossaryJL.html From the glossary of Palaeos,a reference frequently cited in Science Online. LCA: (abbr.) last common ancestor (and all descendants of that ancestor).

http://www.everything-science.com/sci/Forum/topic,1753.0 Earliest Primate May Have Pre-Dated some Dinosaurs (Nature) "We present a new statistical method that suggests a Cretaceous last common ancestor of primates, approximately 81.5 Myr ago, close to the initial divergence time inferred from molecular data.

http://johnhawks.net/weblog/reviews/genetics/genetics_mre_aapa_2005.html analytical papers by Hey and separately by Alan Rogers and colleagues The "ancestral allele" at a given locus is the allele thought to have been carried by the last common ancestor (LCA) of all humans.

http://discovermagazine.com/2005/feb/new-limb-on-family-tree New Limb on Family Tree 02.06.2005 The creature, known scientifically as Pierolapithecus catalaunicus, may be the last common ancestor of the great ape family: gorillas, chimps, orangutans, and humans.

http://www.talkorigins.org/faqs/homs/mtDNA.html Fossil Hominids: mitochondrial DNA However, using the genetic difference to estimate the time of the last common ancestor is difficult, for a couple of reasons. One is that the rate at which mtDNA mutates is poorly measured.

http://www.geocities.com/CapeCanaveral/Lab/2948/tree.html The British biologist Richard Dawkins points out some interesting dates about this. The last common ancestor between men and chimpanzees lived as recently as five million years ago. Our last common ancestor with the carnivores (cats, dogs) lived some 60 million years ago. The last common ancestor between a whale and a pea lived about 2 billion years ago.

Fred, which of these meanings am I "inventing?" 98.196.237.162 (talk) 18:09, 25 November 2007 (UTC)

Tom, these uses of the term LCA mean exactly MRCA. None of these use the term to mean the bifurcation point of modern human and some unspecified XYZ species. You seize LCA and define it in your own way. Let me give you an analogy. Let's say I take the term, the Last Emperor of China of the Qing Dynasty, and I define it as "the person who sat on the throne who was founder of the Qing dynasty, marking the end of some unspecified previous dynasty". Do you think it makes sense? I can google for the term and come up with more than 23,000 pages. Does it mean my definition is correct? Think about it.

If you are not happy with the situation, raise an issue following Wikipedia:Dispute resolution. Be prepare to back up your claim, however. Merely goggling for the term does not automatically give you claims to your own definition of the term. It is clearly from our long exchange here that you do not understand the issue at all. Have you actually read the page I included twice on the deletion of the most ancient common ancestor. Please read this page, and write a few sentences indicating your understanding of why this article was deleted. If you can articulate why that article was deleted, then you can truly claim to have understood what I said. That article tried to define the exact same idea you are vouching for. Are you another Sockpuppet of Robert Young? Fred Hsu (talk) 22:42, 25 November 2007 (UTC)

You say I am self-defining the name. You ask "Where did you read about this definition of LCA that you use to mark your 'seminal' individual?" So I provide several references (including one of your own) naming LCA as the origin of modern humans and then I show papers naming an LCA of primates, an LCA of metazoans, etc. It is a very common way of naming the originator of a species (and all descendants). Why do you keep questioning it? Is it because you still think (very incorrectly) that the LCA of all mankind, ie., the originator of the species, was born a mere 2,000 years ago? And he is the same individual Chang calls the MRCA of all mankind? You have got to get that thought out of your head Fred or you will never be able to move forward. Go back and look at the line chart I drew for you and tell me what you think is wrong with it. Tom Schmal (talk) 04:43, 28 November 2007 (UTC)

Please find in one published article a chart like the one you drew. You misunderstand these papers. They are not talking about founders of species. They are talking about the very last common ancestor shared by a set of animals!!! The very last common ancestor shared by all humans alive today is calculated to have lived not too long ago, because of persistent genetic mixing between geographical areas.

Did you understand the phylogenetic tree I pointed out to you earlier? Do you know what a phylogenetic tree is? Any any branching point, where a single line diverges into two lines leading to species A and B, you are not talking about LCA of A or LCA of B. The branching point defines the LCA (aka MRCA) of all members of A and B, combined. We are talking about the LCA of A and B. By LCA of humans, we mean, find the branching point leading to n number of lines leading to all living individual where n is the number of people alive today. Sigh. Fred Hsu (talk) 08:12, 28 November 2007 (UTC)

Hey, despite your continual <sighs>, I just found another reference. You are going to love this one: "MRCA is now more frequently used to describe common ancestors within a species. On the other hand, LCA now describes the common ancestor between two species."

Fred, you yourself typed those words into your Wikipedia article MRCA on Juy 24th. It is exactly what I am saying is correct! Common ancestor between two species is exactly my definition of LCA! Obviously you are not an expert, but when I see you are saying it too - man I have to ask: why are you going on and on with me? What is your point? Tom Schmal 01:40, 1 December 2007 (UTC)

Sigh. And I am not joking here. That definition you quoted is NOT defining the LCA as the founder of a species. Let me see if I can get this point through to you, again. What the above quote says is: MRCA and LCA are synonyms; both terms are applied to a SET OF THINGS. You need to explicitly list THESE THINGS, either by specifying two or more species, or specify a group such as "all humans". Now, the way to compute either MRCA and LCA is exactly the same; you simply find the last common ancestor of all these THINGS.

Now, let's examine the two points in your Eiffel Tower chart. There is "MRCA of all living humans at 2K" and "LCA of all living humans at 2M". Do you see where the problem is now? The LCA you are trying to pinpoint here is probably MRCA of human and other apes. But the caption should have read "MRCA of human and chimp" or "LCA of human and chimp".

I did not point out all problems with your original article initially. Let me illustrate a few more problems here. Take this one for instance: "While the new species will owe all its genes to its LCA, the LCA itself will be a member of the original line, not the new one" (emphasis mine). How can all living human owe all its genes to a single person? Do you think your LCA cloned itself? This is simply wrong. Please read on up how sexual reproduction, fertilisation and genetic recombination actually work. Perhaps read the book River out of Eden by Dawkins.

Take another one: "‎At its most narrow definition, the LCA is the seminal individual that first coded the mutation that created the characteristic that defined the new species". There is no magical mutation that defines a new species. At the MRCA point, individuals from two future branches can continue to breed. Species are defined in retrospect, after a long time have passed since the two groups of animals last interbred, due to some form of (mostly) physical separation. I think you misunderstand speciation. You seem to believe a single mutation somehow defines a species. This is not how species are defined. There is no magical mutation on a gene which created the human race, as you seem to believe. Again, please read up on the topics of species, speciation and [[human evolution]. Fred Hsu 12:24, 1 December 2007 (UTC)

This is my last reply to you here. I am not going to repeat the same reply over and over, if you persist in your viewpoint without actually understanding the concept. Please tell me which books or articles you ACTUALLY READ from which you absorbed knowledge which you are proselytizing. If you can't give me a single one (I have asked many times already), it is useless for me to continue to discuss this matter further with you. Please submit a request for formal dispute resolution if you wish. Fred Hsu 12:36, 1 December 2007 (UTC)

(I edited above paragraphs to make them more clear). Fred Hsu (talk) 02:24, 5 December 2007 (UTC)

Ok, this will be my last effort also.

You state the "LCA describes the common ancestor between two species," but then you say it is “NOT the founder of a species.” Fred, think! this *has to be* the founder. If not him, then who?

That makes no sense to say that LCA is at the same time the common ancestor between two species and also the founder of a single species. How could the founder of a single species also be ancestor to the descendants of the other species (regardless if that other species has become a third distinct species or not)? That individual can't actually be a member of the species that it is supposed to be the founder of, but must be a member of the ancestral species, otherwise how could it simultaneously be the sire of the other set? And how can we even call any specific individual the "founder" a species anyhow? Isn't the idea of speciation usually in terms of two populations of the same species gradually becoming distinct from each other because they are isolated from each other and do not interbreed, and encounter different selection pressures? The last common ancestor of the two populations is certainly not what I would call a "founder" of any new species, but rather is the most recent common ancestor of those individuals that came to form two populations that in time became distinct enough to be judged as being different species. 207.189.230.42 (talk) 08:56, 24 July 2008 (UTC)

Regarding the Eiffel tower chart (nice name by the way) - sorry, I thought it was obvious the LCA described there is at the split of modern humans and *archaic Homo sapiens*, not chimps. He lived 2 Million – 40,000 years ago, depending on which theory you like, so of course it can't be the LCA of human and chimp as you suggest. That LCA occurred 5-10 million years ago.

Originally you said the LCA of all living humans was born 2-3,000 years ago. Now you say it was 5-10 million. It is kind of a breakthrough for me to realize that you have not actually given much thought to where in time the bifrucation point of truly modern man might be. As the article describes, it is somewhere between the old “missing link” (chimp) of 5-10 million years ago and Chang’s MRCA of All Mankind of 2-5 thousand years ago. I hope this realization is a breakthrough for you, too.

As for the LCA being a single individual spreading a magical gene or an interbreeding group - who knows? The article references Richard (magic gene) Klein but overall takes a neutral point of view rather that the one you espouse above. At any rate it is covered in the section “LCA: a single organism?” And by the way, the article does not say “all living human owe all its genes to a single person,” as you claimed. Still, it is somewhat gratifying to know that a fake quote is one of your biggest complaints!

Fred. it sounds to me you are worried that 999,999 angels, not a million, can dance on the head of a pin. I will keep working on it, so you have done some good here. But just chopping it up and disappearing it, well, that does not make sense. It is a great article! Tom Schmal (talk) 20:40, 9 December 2007 (UTC)

Things to consider - for whoever tries to resolve this dispute

I have promised myself not to post any more useless replies here. Following are things to consider for whoever ends up resolving this dispute. Of course, please do read the entirety of this talk page as well. Fred Hsu (talk) 01:35, 10 December 2007 (UTC)

Tom, please create a new section of your own if you wish to list points for other people to consider, against me. Fred Hsu (talk) 01:35, 10 December 2007 (UTC)

1. The version of article before I pruned it is here. The version as of this moment as I write this paragraph is here.
2. Tom clearly fails to understand how the terms LCA and MRCA are identical, and that they are applied to a closed set of organisms. Just like one cannot say "sum of 1, 2 and 3 = sum of 1 and 2", one cannot say "LCA of humans and chimps = LCA of humans", or "LCA of humans and some unspecific archaic hominid == LCA of humans".
3. Neither LCA or MRCA is used to mean founder of a species. These terms can be applied to genes, species, genera, classes, phyla, etc. There is nothing magical about a 'species'. Using "LCA of humans" to indicate some founder individual of modern human species is not supported by any literature. It is original research.
4. I have not seen one book or one paper show Tom's Eiffel Tower chart. All phylogenetic charts I have ever seen are consistent with LCA = MRCA. Again, Tom can't point to the source of his chart.
5. Tom never responded to my request that he investigate why the most ancient common ancestor article was deleted via the AfD process. I asked Tom to summarize why the article was deleted to show his understanding of the issue at table. He never did. That article tried to use the words most ancient in the same Tom is trying to use the word last here, to define some species founder who is as far back in time from us as possible. Such definition is not supported by any literature as I indicated in AfD page for MACA and on this talk page for LCA.
6. I repeatedly asked where Tom got his idea of LCA, either from books or papers. He never could point to one. He kept pointing to articles and references I added to show LCA = MRCA, and believed that they showed his definition of LCA. Absolutely none supported his idea.
7. As for myself, with regard to my background on this topic, please see following:
   1. my rewrite of MRCA: here, here and here. See the article before and after.
   2. my rewrite of Mitochondrial Eve: here. Article before and after.
   3. expansion of The Ancestor's Tale with summaries for all stories in this book: here and here. Article before and after.
   4. rewrite of River out of Eden: here. Article before and after.
   5. created and wrote Parental expenditure
   6. mammalian cladogram and mammalian phylogenetic tree I created.

Things to consider (from Tom)

Ok, Fred here is my summary

In describing the individual (or founding population) at the bifurcation of two taxonomic groups (eg, of chimps and humans) the literature uses two terms - either the most recent common ancestor or the last common ancestor. In my view, the latter more often used as a proper noun, eg, the LCA. So if (as you say) Wikipedia has room for only one of these terms then the more proper name, LCA, should be the survivor. Defining “most recent common ancestor” is too trivial. Like “most recent fashion,” it does not really require a Wikipedia entry.

The main value in retaining it as an article is the work done in lineage models by Chang and others identifying the Most Recent Common Ancestor of All Mankind. We do not know exactly when the MRCAAM lived, somewhere 2,000 to 5,000 years ago. It would have been handier had Chang dropped the word “Common” from his discovery’s name, but he didn’t. Thus the definition for most recent common ancestor of all living individuals in a species has been taken, and can’t be used to describe someone else.

Which brings us to: Is LCA the proper name for the founder of a species? As I noted in the links above, LCA is commonly used in literature to identify the founder of a taxonomic group. “LCA of primates,” "LCA of all humans," “LCA of metazoans,” even LCA of mtDNA. Above the species level, “MRCA of Primates” is probably equivalent to “LCA of primates.” Below the species level however, MRCA does not work. For example, Chang's MRCA of All Mankind means something else entirely and can’t be used as the name of the founder of the species.

I don’t know if LCA is the only term to describe the founder of a species. “Concestor” might work. “MRCA of all mankind living and dead might work.” But right now LCA as founder of a species is being used in the literature and is the proper subject for a Wikipedia article.

Fred, I am putting out a request for comment. I saw that you had found the links to LCA and replaced them with links to your MRCA article. No wonder you are the only one discussing here! To you who do care to read the original article, the one in question, you may find a copy of it here [1].

 Tom Schmal (talk) 19:28, 14 December 2007 (UTC)

RfC: Should article "Last Common Ancestor" be deleted/merged?

Should article "Last Common Ancestor" be deleted/merged??

Notes to commentators Fred Hsu (talk) 05:18, 17 December 2007 (UTC)

please briefly read all sections on this talk page to get an idea about what happened in the last month to this article.

closing statements from Fred

closing statements from Tom

Requests have been made separately on these pages: evolutionary biology, tree of life and molecular and celular biology WikiProjects.

• I'd say it should merged, or simply redirected, since the article says that the only difference between a "Most Recent Common Ancestor" and a "Last Common Ancestor" is that MRCA can be used within a species and LCA is only used between species. Unless some info about LCAs specifically is presented there is no need for a separate article. [Actually the article says that MRCA is only used within a species, but the cite presented does not support this claim; I shall presently fix the claim.] Deletion would be a bad idea, since LCA is a common enough term. Ben Standeven (talk) 04:37, 30 December 2007 (UTC)

If I understand what I have read correctly, then I have to say that I have problem with the idea of LCA/MRCA having anything to do with whatever a "founder of a species" is supposed to be. Tom speaks of such an individual (1)existing and (2)being the LCA as described. However, the words "founder of a species" strikes me as a dubious concept as if there is always supposed to be an individual that is suddenly so different from its parent(s), and in any case, an LCA for any given two or more species could not logically be a member of a new species that hasn't even evolved into being yet, being merely the ancestor of populations that became different species. The implication is that the "founder" is not actually a member of the species that it is supposed to have founded. 207.189.230.42 (talk) 09:32, 24 July 2008 (UTC)

Where do we vote? The page seems good to me, and the question long settled in favor of Tom. Right now, however, "concestor" is re-directing to the MRCA page, and it should re-direct to this page instead. Concestor = last common ancestor, both mean last common ancestor that is common to two different species. This page does link to MRCA and MRCA should link here. If no one comments otherwise within the week I will make these changes and remove the banner on the article about the debate.Skates61 (talk) 05:52, 16 February 2009 (UTC)

Skates61, I was away from wikiland for a long time. I am back. And will bring this issue to conclusion. I don't know why you said "the question long settled in favor of Tom". Excuse me, have you read through this talk page and the deletion discussions of other related articles as mentioned in the section "Things_to_consider_-_for_whoever_tries_to_resolve_this_dispute"? I will clean up and merge this article into MRCA. In short, MRCA=LCA, but one needs to pay special attention to the "set of individuals/species/genes" for which MRCA is defined. Fred Hsu (talk) 04:11, 6 June 2009 (UTC)

Last couple sentences

For example, computer simulations suggest that every person living today could share a common ancestor who lived as few as 2,000 to 3,000 years ago. This person (name lost to history) has been entitled the Most Recent Common Ancestor (MRCA) of All Mankind. But there have not been any speciation events in Homo sapiens during the past 3,000 years, so this person cannot have been the LCA with any other species.

(Emphasis mine)

This seems unlikely: Asia and Europe were cut off from one another with what was likely quite minimal gene flow by 1000 BC and long before. Sub-Saharan Africa was also cut off, not to mention the more complete isolation Mesoamerica, Australia, &c. To say that we possess a common ancestor 2000-3000 years ago is to say that this founding population must have dispersed and either displaced or mixed with all other human cultures on the earth, since 2000-3000 years ago!! This clearly does not allow for reproductively isolated populations since then. Edit: I noticed the conflict between LCA and MRCA, but this computer simulation still does not seem like evidence to me, i.e. it seems more like what might have been (speculative) than what actually happened (factual). I have also noticed the problem of intermarrying in very recent times, but does this apply to very isolated, rarefied populations like the Negrito, who have effectively resisted foreign influence until the 20th century?

I would have less of a problem with this if it were highlighted that this scenario is completely artificial and oversimplified. --♦♦♦Vlmastra♦♦♦ (talk) 03:26, 8 January 2008 (UTC)

I notice that the issue is dealt with more satisfactorily here.--♦♦♦Vlmastra♦♦♦ (talk) 04:06, 8 January 2008 (UTC)

Yes, I think the MRCA article has more complete and accurate descriptions of related concepts. And it contains proper inline citations for all paragraphs. This is, mhm, because I took the pain to rewrite in a while back ;) Joking aside, you may want to check out Dawkins's The Ancestor's Tale for more accessible information. Fred Hsu (talk) 04:47, 8 January 2008 (UTC)

Fred, please. This place is for outside comments. Tom Schmal (talk) 14:59, 12 January 2008 (UTC)

Tom, it's not. This is a new section. I moved your comment down one line and properly indented it. Please follow the wikipedia styles when you write, both on article pages and on talk pages. Fred Hsu (talk) 13:34, 13 January 2008 (UTC)

"The LCA of elephant and earthworm, for example, lived an ancient 600 billion years ago" This is not possible. The universe has no been around for this amount of time. —Preceding unsigned comment added by 115.129.9.169 (talk) 12:33, 12 March 2009 (UTC)

Merging LCA into MRCA

As explained in previous talk sections, MRCA=LCA generally. And the MRCA article has more complete, more accurate description of concepts with properly written paragraphs and citations. I will now examine both articles and make sure we don't lose anything important and correct in LCA during this transition. For reference, the current version of LCA at the time of this transition is this version. Fred Hsu (talk) 05:57, 6 June 2009 (UTC)