# Which living reptile is most closely related to homo sapiens s.? **URL:** \ **Category:** Factual Questions\ **Created:** [October 10, 2011, 5:01pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199 "2011-10-10T17:01:55Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 10, 2011, 7:55pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/41 "2011-10-10T19:55:22Z")
> [@Colibri](#): > > Yes, it does. So an iguana and snapping turtle are the same thing because they belong to the same clade? The OP is not asking about the relationship between humans and an entire clade, but one specific species to another. ---
**Author:** ![Yllaria](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yllaria/32/3452_2.png) [@Yllaria](https://boards.straightdope.com/u/Yllaria)\ **Post date:** [October 10, 2011, 8:00pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/42 "2011-10-10T20:00:21Z")
All of your seventh cousins are equally related to you even if one of them looks a lot like his great-great-grandfather. His great-great-grandfather was more closely related to you, but he’s dead. And what you decided makes this cousin more like his great-great-grandfather will be arbitrary. He may have the same look to his nose, eyes, and jaw, but have a different blood type, different height, and an extra finger on each hand. Time goes forward. Changes happen with time. None of your seventh cousins are closer to being their ancestors (and therefore, more related to you) than any of the others in any way that’s meaningful to measure. That said, if you look at not seventh cousins but all cousins your age (modern cousins), you’ll be comparing some fifth or sixth cousins with seventh or eighth cousins. The fifth cousins are more closely related (even if they look nothing like great^X grandpa). That’s easy to pick out with modern records, but harder to do with fossils. ---
**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:** [October 10, 2011, 8:08pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/43 "2011-10-10T20:08:12Z")
> [@TriPolar](#): > > So an iguana and snapping turtle are the same thing because they belong to the same clade? Effectively, yes. As was mentioned upthread, whatever traits we share with an iguana are going to be shared between us and a snapping turtle, as well, on account of us all being amniotes. There won’t be any definitive traits which could place either a snapping turtle or an iguana closer to us than the other is. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 10, 2011, 8:11pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/44 "2011-10-10T20:11:37Z")
> [@Colibri](#): > > Yes, it does. Just to expand (although it’s already been said) you are insisting on changing the definition of “related to.” In both taxonomy and genealogy, the degree of relationship is determined with reference to the most recent common ancestor. The degree of genetic similarity is just that - the degree of genetic similarity - not relationship. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 10, 2011, 8:14pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/45 "2011-10-10T20:14:36Z")
> [@TriPolar](#): > > So an iguana and snapping turtle are the same thing because they belong to the same clade? With reference to humans, yes. With reference to other reptiles, no. > [@](#): > > The OP is not asking about the relationship between humans and an entire clade, but one specific species to another. And we have answered the question. Humans are equally related to all species of reptiles. That’s the answer, even if you don’t want to accept it. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [October 10, 2011, 8:20pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/46 "2011-10-10T20:20:51Z")
Do we have a good idea of what the most recent common ancestor of reptiles and mammals even looked like? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 10, 2011, 8:21pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/47 "2011-10-10T20:21:28Z")
> [@](#): > > So, if you want to take your argument to its logical conclusions, you would need to find the particular, individual human who was most closely related to the particular, individual reptile. > > In that case, though, we all know it’s Karl Rove. Is he the particular human or the particular reptile? ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [October 10, 2011, 8:27pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/48 "2011-10-10T20:27:00Z")
> [@Toucanna](#): > > Thanks for the prompt replies. > > But I guess I haven’t explained myself clearly enough. If I understand evolutionary theory correctly (and it’s possible I do not), all life on earth descended from one living form/entity/creature. Therefore, every living thing on earth is related to each other, to some degree. > > So, which species of reptile, currently in existence, is the one most closely related (however distant that relationship is) to h.s.s.? ETA: if the species cannot be identified, then genus or clade or something similar would be nice to know. > > Now tell me where I’ve misunderstood the concept or have made an incorrect assumption. 😃 This is like asking which of my father’s brother’s children is more closely related to me. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [October 10, 2011, 8:29pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/49 "2011-10-10T20:29:07Z")
> [@AndrewL](#): > > Do we have a good idea of what the most recent common ancestor of reptiles and mammals even looked like? [Therapsids](http://en.wikipedia.org/wiki/Therapsida). the picture makes them look like an unfriendly cross between a cat and a monitor lizard. ---
**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:** [October 10, 2011, 8:40pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/50 "2011-10-10T20:40:43Z")
Therapsids aren’t basal amniotes, they are basal synapsids. Reptiles and mammals had already split apart by then, and therapsids are firmly on the mammal side, even though they aren’t true mammals. ---
**Author:** ![AndrewL](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AndrewL](https://boards.straightdope.com/u/AndrewL)\ **Post date:** [October 10, 2011, 8:41pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/51 "2011-10-10T20:41:32Z")
> [@Inigo\_Montoya](#): > > [Therapsids](http://en.wikipedia.org/wiki/Therapsida). the picture makes them look like an unfriendly cross between a cat and a monitor lizard. Therapsids are basal to all mammals, but from what I can gather the reptiles had split off well before the Therapsids developed. I don’t know if there are any good fossil indications of what the common ancestor of Therapsida and reptiles looked like. ---
**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:** [October 10, 2011, 8:45pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/52 "2011-10-10T20:45:37Z")
> [@Inigo\_Montoya](#): > > [Therapsids](http://en.wikipedia.org/wiki/Therapsida). the picture makes them look like an unfriendly cross between a cat and a monitor lizard. Therapsids were full-on synapsids. The common ancestor would actually have looked more lizardy, like [_Casineria_](http://en.wikipedia.org/wiki/Casineria). ---
**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:** [October 10, 2011, 8:47pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/53 "2011-10-10T20:47:46Z")
This wikipedia article could be helpful: [Amniote - Wikipedia](http://en.wikipedia.org/wiki/Amniote). The common ancestor of synapsids (the grab-bag of mammals and mammal-like critters) and reptiles probobly looked like a pretty standard lizardy critter. If you saw one in a zoo and the the label said “lizard”, you wouldn’t raise an eyebrow. You’d have to really dissect the thing to determine exactly why it isn’t a lizard, just like, say, a t[uatara](http://en.wikipedia.org/wiki/Tuatara) isn’t a lizard, it just looks like a lizard. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [October 10, 2011, 8:48pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/54 "2011-10-10T20:48:46Z")
> [@AndrewL](#): > > Do we have a good idea of what the most recent common ancestor of reptiles and mammals even looked like? Pretty much like a lizard. The earliest amniote known was [Hylonomus](http://en.wikipedia.org/wiki/Hylonomus). The earliest member of the lineage that led to the mammals, the synapsids, was [Archaeothyris](http://en.wikipedia.org/wiki/Archaeothyris). I haven’t found any illustrations of the earliest members of the Sauropsida, the clade that led to Reptilia, but I’m sure they weren’t much different externally. ---
**Author:** ![psychonaut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/psychonaut/32/4655_2.png) [@psychonaut](https://boards.straightdope.com/u/psychonaut)\ **Post date:** [October 10, 2011, 9:48pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/55 "2011-10-10T21:48:06Z")
> [@Colibri](#): > > There is also no way to equate the different kinds of changes (e.g. point mutations vs chromosome alterations). Which species is more closely related to another, one that has 10 point mutations in a non-coding region, or one that has undergone a chromosomal translocation? The latter could have a much greater effect. So saying there is a particular number of changes between two forms is pretty much meaningless. Without further qualification, yes. It’s like asking which of two editions of a book is more closely related to the author’s original manuscript–one where there are ten spelling mistakes in various words, or one where two pages have been swapped. But as long as you identify each possible type of error and assign some arbitrary weight to them, there’s no reason you can’t just count them up to quantify the similarity of any two texts. Yes, it’s arbitrary, but it’s internally consistent, and may well allow one to draw meaningful inferences about the real world. This process, known as [edit distance](http://en.wikipedia.org/wiki/Edit_distance), is used all the time in computer science and related fields (such as mine, computational linguistics), and I would be very surprised if it has not already been applied to genetic sequences in bioinformatics. Wikipedia has an article on [distance matrices in phylogeny](http://en.wikipedia.org/wiki/Distance_matrices_in_phylogeny) which seems to be relevant, though as I’m no geneticist I can’t say for sure. ---
**Author:** ![Bearflag70](https://avatars.discourse-cdn.com/v4/letter/b/8e7dd6/32.png) [@Bearflag70](https://boards.straightdope.com/u/Bearflag70)\ **Post date:** [October 10, 2011, 10:03pm UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/56 "2011-10-10T22:03:58Z")
sleestak ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 11, 2011, 2:46am UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/57 "2011-10-11T02:46:08Z")
> [@Colibri](#): > > Just to expand (although it’s already been said) you are insisting on changing the definition of “related to.” In both taxonomy and genealogy, the degree of relationship is determined with reference to the most recent common ancestor. The degree of genetic similarity is just that - the degree of genetic similarity - not relationship. Genetically, all life on earth is related, and although we do not have the information, their is a genetic relationship that is established with each generation. Genealogy uses this to determine the relationship of cousins, people who share a common ancestor. You are not as closely related to all of humanity as you are to your first cousin. Now taxonomic systems differ, and certainly some are no better at determining genetic relationships than your bathroom scale can define your height, but that does mean that all people are the same height. > [@Colibri](#): > > And we have answered the question. Humans are equally related to all species of reptiles. That’s the answer, even if you don’t want to accept it. The answer is that you don’t know, and are attempting cover that up with a silly semantic argument. I’ve already explained several times that there is a definitine genetic relationship between any two animals that ever lived. > [@Darwins\_Finch](#): > > Sure, but you cannot, based on the magnitude of the number of differences alone, even if they _were_ measurable, infer relative relationships for very distant relatives. It may take x changes to get from Ancestral Reptile to Derived Reptile A, and y changes from AR to Derived Reptile B, but there is no universal law stating that if x \< y, A is more closely related to AR than B is. Evolution does not always take the most direct genetic pathway, and those meanderings can be longer or shorter in differing lineages. > [@Colibri](#): > > There is also no way to equate the different kinds of changes (e.g. point mutations vs chromosome alterations). Which species is more closely related to another, one that has 10 point mutations in a non-coding region, or one that has undergone a chromosomal translocation? The latter could have a much greater effect. So saying there is a particular number of changes between two forms is pretty much meaningless. You can’t give an exact answer because of the lack of evidence as I’ve said several times. But cladistics are actually a means of making the qualitative comparisons and explaining the distance between species or specific animals. But apparently the experts in cladistics here don’t want to share that information. [qyote] True. Generation time can make some difference to branching rate, and is sometimes taken into account in trying to estimate the time since clades have diverged. [/QUOTE] Except occasionally when realizing how the flaw in their argument. > [@Frylock](#): > > This is like asking which of my father’s brother’s children is more closely related to me. No, this is asking if a brother’s children are more closely related to a person than his brother’s grandchildren. Unless there’s a Chinatown situtation going on, this person is more closely related to his brother’s children than his brother’s grandchildren. > [@psychonaut](#): > > Without further qualification, yes. It’s like asking which of two editions of a book is more closely related to the author’s original manuscript–one where there are ten spelling mistakes in various words, or one where two pages have been swapped. But as long as you identify each possible type of error and assign some arbitrary weight to them, there’s no reason you can’t just count them up to quantify the similarity of any two texts. Yes, it’s arbitrary, but it’s internally consistent, and may well allow one to draw meaningful inferences about the real world. This process, known as [edit distance](http://en.wikipedia.org/wiki/Edit_distance), is used all the time in computer science and related fields (such as mine, computational linguistics), and I would be very surprised if it has not already been applied to genetic sequences in bioinformatics. Wikipedia has an article on [distance matrices in phylogeny](http://en.wikipedia.org/wiki/Distance_matrices_in_phylogeny) which seems to be relevant, though as I’m no geneticist I can’t say for sure. And genetically there is an definitie path between any two animals which does not require interpretation. We just don’t have all the intermediate manuscripts in this case, but there are ways to make reasonable guesses, or at least state the truth, that the answer is unknown. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [October 11, 2011, 2:59am UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/58 "2011-10-11T02:59:05Z")
> [@Darwins\_Finch](#): > > Therapsids were full-on synapsids. The common ancestor would actually have looked more lizardy, like [_Casineria_](http://en.wikipedia.org/wiki/Casineria). Surprisingly, a Bing image search for “casineria” is NSFW! ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 11, 2011, 3:06am UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/59 "2011-10-11T03:06:57Z")
> [@Frylock](#): > > Surprisingly, a Bing image search for “casineria” is NSFW! You’ll have to give us a URL. I’m only getting SFW stuff. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [October 11, 2011, 3:26am UTC](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199/60 "2011-10-11T03:26:40Z")
[Here you go, you naughty boy.](http://www.bing.com/images/search?q=casineria&FORM=BIFD) [Previous page](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199.md?page=2) [Next page](https://boards.straightdope.com/t/which-living-reptile-is-most-closely-related-to-homo-sapiens-s/599199.md?page=4)