# Most recent common ancestor of all living birds **URL:** \ **Category:** Factual Questions\ **Created:** [July 15, 2014, 11:10pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234 "2014-07-15T23:10:52Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [July 17, 2014, 7:24pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/41 "2014-07-17T19:24:08Z")
> [@Mangetout](#): > > No it doesn’t (the graped part) - evolution doesn’t work like that. Selection can only occur from things that are there to be selected. If other creatures never developed a mutation for a proto-beak, then it couldn’t be selected, and it doesn’t matter if it would have been better than what they had. Well, except that things like Flight have shown up over and over- bats, birds, reptiles, insects, etc. ---
**Author:** ![EdwinAmi](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@EdwinAmi](https://boards.straightdope.com/u/EdwinAmi)\ **Post date:** [July 17, 2014, 7:34pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/42 "2014-07-17T19:34:33Z")
interesting thingy: boffins manipulated chickens’ genomes (I think they got one specific gene that was already there to be expressed), and got chicks in eggs that grew teeth ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [July 17, 2014, 7:35pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/43 "2014-07-17T19:35:54Z")
> [@OldGuy](#): > > The usual argument I see gives a simple tree and says see we call both of the things below this node dinosaurs and birds descend from just one of those types of things so you have to call birds dinosaurs, too. > > But the argument has to be more than that. I’m you can draw the same type of tree for reptiles and mammals. Mammals descend from one particular group of reptiles so if you want to say both types of reptiles are reptiles you have to include mammals. Now maybe evolutionary biologists do say that or something similar, but the only thing I see them beat us up over is “birds are dinosaurs” not “dogs are reptiles”. Thing is, the classic “fish, amphibian, reptile, mammal, bird” classes don’t line up with reality. Some trees put synapsids–the base group that includes modern mammals–as more closely related to diapsids (lizards|snakes|crocodiles|dinosaurs|birds) than those groups are related to turtles (anapsids). This would make mammals into reptiles, if we wanted to bother keeping the term reptile as a phylogenetic name rather than a descriptive term. But almost all modern trees put turtles as more closely related to the above group than they are to synapsids, this tree shows this theory: [https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3Ab0005720d771053de01f08262d4f22707cd194e68b3854b0504cdc34%2BIMAGE\_THUMB\_POSTCARD%2BIMAGE\_THUMB\_POSTCARD.1](https://dr282zn36sxxg.cloudfront.net/datastreams/f-d%3Ab0005720d771053de01f08262d4f22707cd194e68b3854b0504cdc34%2BIMAGE_THUMB_POSTCARD%2BIMAGE_THUMB_POSTCARD.1) Which means reptiles can be kept as long as we’re willing to call birds a specialized type of reptile. If you don’t want to call birds reptiles, then we have to get rid of the idea of reptile. A better term than “reptile” would be “Amniotes”, which includes mammals, mammal-like reptiles, reptiles, birds, and so on, but not amphibians. “Tetrapods” would include the various types of amphibians but not fish. Here’s a tree that presents this view: [http://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/Vertebrata\_cladogram2.png](http://www.ucl.ac.uk/museums-static/obl4he/vertebratediversity/Vertebrata_cladogram2.png). Notice some fudging–some of these branches are three pronged rather than two pronged. The point is, words mean whatever we agree that they mean, and they can mean different things in different contexts. I wouldn’t be confused if someone showed me a bone from their backyard and said “This isn’t a reptile bone, it’s a bird bone”, despite the fact that I know birds are a kind of reptile. The only time I might be confused is if it was a Jurassic or Cretaceous fossil, then we’d have to agree on what we mean when we use the words “bird” and “reptile”. ---
**Author:** ![EdwinAmi](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@EdwinAmi](https://boards.straightdope.com/u/EdwinAmi)\ **Post date:** [July 17, 2014, 7:52pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/44 "2014-07-17T19:52:19Z")
I classify animals in order of cuteness At the top of the list is bunnies followed by dogs, cats, bears, porcupines, wombats and so on. The least cute are on the bottom It’s a much more useful taxonomy ---
**Author:** ![Chief\_Pedant](https://avatars.discourse-cdn.com/v4/letter/c/a6a055/32.png) [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)\ **Post date:** [July 17, 2014, 9:16pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/45 "2014-07-17T21:16:25Z")
> [@iiandyiiii](#): > > This sounds like exactly the same thing. How is LCA different than MRCA? The “most recent” is the “last”, and vice versa. I understand one is used, in general, for intra-species, and the other for inter-species, but they both call for the same creature. > > This (CP’s example of how the MRCA is used in humans) seems completely irrelevant to the thread. > > I’ve read the Ancestor’s Tale, by the way – one of my favorite books on evolution and science. As long as one doesn’t mix up the difference between a genealogical ancestor and a genetic ancestor, it’s strictly a (pedantic 😉 ) usage difference. However, when one is talking about the ancestor of more than one species, LCA is preferred to help make this distinction. From [Wikipedia,](http://en.wikipedia.org/wiki/Most_recent_common_ancestor)e.g.: \*“It is also possible to use the term MRCA to describe the common ancestor of two or more different species. In the past, the term MRCA was used interchangeably with last common ancestor (LCA) to denote both the common ancestor within a species and that between species. But 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.” \* I sort of think of the LCA as the anchor point from which SNP variations drove the assortment of descended species. I’ve seen discussions elsewhere on the SDMB where people get confused about the term MRCA and make an assumption it implies the MRCA is the source of the descendants’ ancestral genes… ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [July 18, 2014, 11:08am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/46 "2014-07-18T11:08:35Z")
> [@DrDeth](#): > > Well, except that things like Flight have shown up over and over- bats, birds, reptiles, insects, etc. _Toothlessness_ also shows up multiple times - in birds, in _Quetzalcoatlus_ and _Pteranodon_ pterosaurs, turtles… Some non-avian dinosaurs like ceratopsians, and some theraspid proto-mammals like _[Diictodon](http://en.wikipedia.org/wiki/Diictodon)_ were part-way there, too. ---
**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\ **Post date:** [July 18, 2014, 12:34pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/47 "2014-07-18T12:34:46Z")
> [@Mangetout](#): > > (the graped part) I saw what you did there, you retro sweetie, you. 🙂 ---
**Author:** ![Dvd\_Avins](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dvd\_Avins](https://boards.straightdope.com/u/Dvd_Avins)\ **Post date:** [February 8, 2017, 8:09am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/48 "2017-02-08T08:09:22Z")
> [@Mangetout](#): > > Only because ‘fish’ is so broad and inclusive a collection as to be a useless term outside of the kitchen. Terms that describe the body plan and function of organisms are not what interest cladists, but not interesting cladists is a far different think than being useless. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 9, 2017, 4:30am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/49 "2017-02-09T04:30:40Z")
> [@iiandyiiii](#): > > Sure, though by the same logic humans are fish (which, if I understand correctly, is true in cladistics). No - in cladistics, “fish” is simply not a valid clade, being paraphyletic. ---
**Author:** ![Captain\_Amazing](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@Captain\_Amazing](https://boards.straightdope.com/u/Captain_Amazing)\ **Post date:** [February 9, 2017, 4:50am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/50 "2017-02-09T04:50:22Z")
> [@MrDibble](#): > > No - in cladistics, “fish” is simply not a valid clade, being paraphyletic. Maybe, but can we still be rodents? It’s a bird! It’s a plane! It’s Superprimate! ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 9, 2017, 5:00am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/51 "2017-02-09T05:00:38Z")
> [@Captain\_Amazing](#): > > Maybe, but can we still be rodents? We’ve never been rodents. And I think you mean “Supraprimate!”😉 ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [February 9, 2017, 5:52am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/52 "2017-02-09T05:52:34Z")
> [@DrDeth](#): > > Well, except that things like Flight have shown up over and over- bats, birds, reptiles, insects, etc. Unless I’m missing something, true flight has evolved three separate times: insects, dinosaurs (obviously inclusive of birds), and bats. Flying fish don’t fly, but glide, and spiders balloon. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [February 9, 2017, 6:22am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/53 "2017-02-09T06:22:22Z")
> [@Derleth](#): > > Unless I’m missing something, true flight has evolved three separate times: insects, dinosaurs (obviously inclusive of birds), and bats. Flying fish don’t fly, but glide, and spiders balloon. Pterosaurs aren’t dinosaurs, and evolved flight separately from them. So that’s 4. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [February 9, 2017, 6:44am UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/54 "2017-02-09T06:44:08Z")
> [@MrDibble](#): > > Pterosaurs aren’t dinosaurs, and evolved flight separately from them. So that’s 4. Interesting. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [February 9, 2017, 6:05pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/55 "2017-02-09T18:05:49Z")
> [@MrDibble](#): > > Pterosaurs aren’t dinosaurs, . For a certain definition of “dinosaur”. phylogenetic taxonomy. Let face it Sir Richard Owen screwed up when he lumped Ornithischia and Saurischia. Nor are dinosaurs "lizards’, nor are they all huge. He was operating on inadequate info. If he hadnt made that mistake we wouldnt have to use the awkward phrase “non avian dinosaur” nor would we have to put up with pedantic assholes who will always point out that “birds are dinosaurs”. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [February 9, 2017, 6:15pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/56 "2017-02-09T18:15:48Z")
> [@DrDeth](#): > > If he hadnt made that mistake we wouldnt have to use the awkward phrase “non avian dinosaur” nor would we have to put up with pedantic assholes who will always point out that “birds are dinosaurs”. What possible way could you monophyleticly define dinosaurs that does _not_ include birds? (Says a proudly pedantic asshole) ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [February 9, 2017, 6:17pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/57 "2017-02-09T18:17:16Z")
> [@Darren\_Garrison](#): > > What possible way could you monophyleticly define dinosaurs that does _not_ include birds? (Says a proudly pedantic asshole) You dont. You dont give a fuck for phylogenetic taxonomy. You go by Linnean definitions and by common usage. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [February 9, 2017, 6:32pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/58 "2017-02-09T18:32:13Z")
> [@DrDeth](#): > > You dont. You dont give a fuck for phylogenetic taxonomy. You go by Linnean definitions and by common usage. They why use that new-fangled Linnean system? Why not describe animals the way they were defined by Aristotle, or Leviticus? ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [February 9, 2017, 6:50pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/59 "2017-02-09T18:50:09Z")
> [@DrDeth](#): > > You dont. You dont give a fuck for phylogenetic taxonomy. You go by Linnean definitions and by common usage. Linnaean classification is gradistic, rather than cladistic. As such, it paid little attention to the phylogenetics of any group, and simply classified animals based on relative degrees of “sameness”. Linnaeus is dead. His classification scheme ought to be, as well. And “common usage” is a non-starter, since the whole idea of binomial nomenclature in the first place was to get away from having a dozen “common names” for every living thing. Common usage also tells us literally nothing about the relationships between organisms. ---
**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\ **Post date:** [February 9, 2017, 6:57pm UTC](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234/60 "2017-02-09T18:57:11Z")
> [@DrDeth](#): > > Let face it Sir Richard Owen screwed up when he lumped Ornithischia and Saurischia. Nor are dinosaurs "lizards’, nor are they all huge. > > He was operating on inadequate info. Info which has, on numerous occasions since, been corroborated; Dinosauria is confirmed to be a monophyletic clade. Owen did make a lot of mistakes, but that wasn’t one. [Previous page](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234.md?page=2) [Next page](https://boards.straightdope.com/t/most-recent-common-ancestor-of-all-living-birds/693234.md?page=4)