# What animal is the common ancestor of humans and horses **URL:** \ **Category:** Factual Questions\ **Created:** [October 16, 2015, 8:33pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842 "2015-10-16T20:33:08Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 16, 2015, 8:33pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/1 "2015-10-16T20:33:08Z")
We are both mammals, what animal can both life forms trace their lineage back to? ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [October 16, 2015, 8:45pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/2 "2015-10-16T20:45:30Z")
I’ve found on [Wikipedia](https://en.wikipedia.org/wiki/Boreoeutheria): > [@](#): > > Boreoeutheria (synonymous with Boreotheria) (Greek: βόρειο “north” + ευ “good” + θεριό “beast”) is a clade (magnorder) of placental mammals that is composed of the sister taxa Laurasiatheria (most hoofed mammals, most pawed carnivores, and several other groups) and Euarchontoglires (Supraprimates). Middle Cretaceous ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [October 16, 2015, 9:52pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/3 "2015-10-16T21:52:11Z")
> [@watchwolf49](#): > > Boreoeutheria] Which has the additional trivia perk of being a word with four consecutive vowels, none of them silent nor diphthongs. ---
**Author:** ![Fubaya](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@Fubaya](https://boards.straightdope.com/u/Fubaya)\ **Post date:** [October 16, 2015, 10:44pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/4 "2015-10-16T22:44:39Z")
Not the Centaur? ---
**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 16, 2015, 10:49pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/5 "2015-10-16T22:49:45Z")
> [@Fubaya](#): > > Not the Centaur? Other way round. Humans and horses are the ancestors of centaurs. ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [October 16, 2015, 11:03pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/6 "2015-10-16T23:03:48Z")
> [@watchwolf49](#): > > I’ve found on [Wikipedia](https://en.wikipedia.org/wiki/Boreoeutheria): > > Middle Cretaceous So what did the MRCA boreoeutherian look like. An undistinguished rodenty thing, I suppose. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [October 17, 2015, 3:17am UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/7 "2015-10-17T03:17:31Z")
No-one has found a fossil of one yet, though this 2013 image by Carl Buell seems to be an extrapolation of what it may have looked like. > **[Tracing the Face and Age of the Placental Mammal Ancestor | AMNH](http://www.amnh.org/explore/news-blogs/research-posts/tracing-the-face-and-age-of-the-placental-mammal-ancestor)** > > A small, furry-tailed, insect-eating creature was the earliest ancestor of placental mammals, according to a new study. Also you can search for images of _Eomaia_, a somewhat earlier mammal that has been found, and looks a bit similar. ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [October 17, 2015, 5:20am UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/8 "2015-10-17T05:20:22Z")
> [@eburacum45](#): > > No-one has found a fossil of one yet, though this 2013 image by Carl Buell seems to be an extrapolation of what it may have looked like. > [Tracing the Face and Age of the Placental Mammal Ancestor | AMNH](http://www.amnh.org/explore/news-blogs/research-posts/tracing-the-face-and-age-of-the-placental-mammal-ancestor) > > Also you can search for images of _Eomaia_, a somewhat earlier mammal that has been found, and looks a bit similar. If no one knows what they looked like, how do we know Eomaia “looks a bit similar?” ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [October 17, 2015, 6:34am UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/9 "2015-10-17T06:34:10Z")
> [@Sailboat](#): > > If no one knows what they looked like, how do we know Eomaia “looks a bit similar?” We know because we have a few fossils of very early placental mammals, and they all tend to be small and rodent-like. We can be virtually certain of that, because few if any larger land animals survived the Chixculub impact event. So the MRCA of horses and primates can’t have looked much different from any known ancestral mammal of the same period. I think it’s similar to what historic linguists do in reconstructing dead languages. For example, from working backwards through known sound changes in various Germanic languages, they can offer a reasonable approximation of Proto-Germanic. And in much the same way they can work their way back to PIE. The difference is that paleontologists do have a few specimens to begin with, while linguists do not, in the case of languages that died out before the advent of writing. ---
**Author:** ![Lucas\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lucas_jackson/32/303_2.png) [@Lucas\_Jackson](https://boards.straightdope.com/u/Lucas_Jackson)\ **Post date:** [October 17, 2015, 6:54am UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/10 "2015-10-17T06:54:17Z")
They’ve named an animal they don’t even have direct evidence for? How strange. ETA: didn’t see SoPs post. . ---
**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:** [October 17, 2015, 9:42am UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/11 "2015-10-17T09:42:03Z")
> [@jtur88](#): > > Which has the additional trivia perk of being a word with four consecutive vowels, none of them silent nor diphthongs. isn’t the -eu- a diphthong? ---
**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 17, 2015, 2:01pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/12 "2015-10-17T14:01:22Z")
We do have direct evidence for the existence of this animal: Humans and horses both indisputably exist, and so their common ancestor must. ---
**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:** [October 17, 2015, 5:53pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/13 "2015-10-17T17:53:55Z")
> [@Chronos](#): > > We do have direct evidence for the existence of this animal: Humans and horses both indisputably exist, and so their common ancestor must. That’s not _direct_ evidence. That’s logical inference. ---
**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 17, 2015, 6:28pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/14 "2015-10-17T18:28:00Z")
Eh, what do you count as direct? If you see a live animal prancing about, you’re just inferring its existence from the pattern of photons hitting your retina. If something that comes from the animal (in this case, the photons) is enough to be considered “direct”, then why isn’t something else that comes from the animal (its descendants) direct? ---
**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 17, 2015, 7:07pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/15 "2015-10-17T19:07:29Z")
> [@White SIFL](#): > > They’ve named an animal they don’t even have direct evidence for? How strange. To clarify, the animal shown in the _Science_ article is not named. It is a composite based on the characteristics of its descendants. [Eomaia](https://en.wikipedia.org/wiki/Eomaia) is based on an actual fossil, but it is a little farther down the family tree of placentals. Boreoeutheria is not a single species, but a name for the clade that includes the ancestors of horses and primates. > [@Chronos](#): > > We do have direct evidence for the existence of this animal: Humans and horses both indisputably exist, and so their common ancestor must. > [@Chronos](#): > > Eh, what do you count as direct? If you see a live animal prancing about, you’re just inferring its existence from the pattern of photons hitting your retina. If something that comes from the animal (in this case, the photons) is enough to be considered “direct”, then why isn’t something else that comes from the animal (its descendants) direct? Without getting into semantic nitpicking, let’s say we don’t have physical evidence of the ancestor itself. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [October 17, 2015, 10:46pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/16 "2015-10-17T22:46:30Z")
> [@TriPolar](#): > > Other way round. Humans and horses are the ancestors of centaurs. Don’t judge me. ---
**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:** [October 18, 2015, 4:10pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/17 "2015-10-18T16:10:47Z")
> [@Chronos](#): > > Eh, what do you count as direct? If you see a live animal prancing about, you’re just inferring its existence from the pattern of photons hitting your retina. If something that comes from the animal (in this case, the photons) is enough to be considered “direct”, then why isn’t something else that comes from the animal (its descendants) direct? Are you being serious? ---
**Author:** ![Peremensoe](https://avatars.discourse-cdn.com/v4/letter/p/ce7236/32.png) [@Peremensoe](https://boards.straightdope.com/u/Peremensoe)\ **Post date:** [October 18, 2015, 4:55pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/18 "2015-10-18T16:55:33Z")
> [@Colibri](#): > > Boreoeutheria is not a single species, but a name for the clade that includes the ancestors of horses and primates. As well as all their descendants, extinct or extant. _We_ are boreoeutherians. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [October 18, 2015, 5:18pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/19 "2015-10-18T17:18:35Z")
Can mitochondrial DNA be used to determine when horses and humans split apart? How many MYA would that have been? ---
**Author:** ![John\_Mace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_mace/32/185_2.png) [@John\_Mace](https://boards.straightdope.com/u/John_Mace)\ **Post date:** [October 18, 2015, 5:59pm UTC](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842/20 "2015-10-18T17:59:22Z")
> [@Wesley\_Clark](#): > > Can mitochondrial DNA be used to determine when horses and humans split apart? How many MYA would that have been? From the link in the first reply to this thread: > [@](#): > > The common ancestor of Boreoeutheria lived between 100 and 80 million years ago [Next page](https://boards.straightdope.com/t/what-animal-is-the-common-ancestor-of-humans-and-horses/734842.md?page=2)