On the trail of a man-eating megatherium


A view from inside the cave in which the "Yemisch" remains were found. [source]

It was not so long ago that tales of an awful creature that stalked the pampas of Patagonia were commonly told. It was difficult, if not impossible, to find anyone who had actually seen it, but many knew of its fearsome power. It was called the Yemisch, and it was a predator that preferred to disembowel its prey. One moment a person or some cattle would be crossing the stream and the next the water would be a blood-red boil. All that was usually left of the victims were greasy entrails floating their way downstream.

That such a creature existed was confirmed by a discovery made in January 1895 near Last Hope Inlet in Chile. Near the entrance of a cave a group of men found a large piece of skin, about five feet long and three feet wide, covered with coarse hair and pockmarked with tough ossicles. This must have been the skin of the Yemisch. The jerky-like bits were divvied up among the discoverers and fame of their find spread.


A cross-section of the giant sloth hide from the cave at Last Hope Inlet. [source]

Sooner or later word of the find reached the eminent South American paleontologist Florention Ameghino, and he quickly recognized the type of animal the skin belonged to. In 1898 the Argentine naturalist identified the skin as belonging to a giant ground sloth. That this was true was backed up by a story he knew of a man named Ramon Lista who said he had seen a giant pangolin trundling about the pampas. It could not have been a pangolin, Ameghino knew, but was instead the Yemisch of the native people and the giant ground sloth of scientists. In his report Ameghino wrote;

Lately, several little ossicles have been brought to me from Southern Patagonia, and I have been asked to what animal they could belong. What was my surprise on seeing in my hand these ossicles in a fresh state, and, notwithstanding that, absolutely similar to the fossil dermal ossicles of the genus Mylodon, except only that they are of smaller size, varying from nine to thirteen or fourteen millimeters across. I have carefully studied these little bones from every point of view without being able to discern any essential difference from those found in a fossil state.

These ossicles were taken from a skin, which was unfortunately incomplete, and without any trace of the extremities. The skin, which was found on the surface of the ground, and showed signs of being exposed for several months to the action of the air, is in part discolored. It has a thickness of about two centimeters, and is so tough that it is necessary to employ an axe or a saw in order to cut it. The thickest part of the skin is filled by the little ossicles referred to, pressed one against the other, presenting on the inner surface of the skin an arrangement similar to the pavement of a street. The exterior surface shows a continuous epidermis, not scaly, covered with coarse hair, hard and stiff, having a length of four to five centimeters and a reddish tint turning toward gray.

The skin indeed belongs to the pangolin which Lista saw living. This unfortunate traveler lost his life, like CreVaux, in his attempt to explore the Pilcomayo, and until the present time he is the only civilized person who has seen the mysterious edentate of Southern Patagonia alive; and to attach his name appropriately to the discovery, I call this surviving representative of the family Mylodontidae Neomylodon listai.

Now that there are certain proofs of its existence, we hope that the hunt for it will not be delayed, and that before long we may be able to present to the scientific world a detailed description of this last representative of a group which has of old played a preponderating part in the terrestrial faunas which have succeeded each other on South American soil.

Ameghino's hypothesis was confirmed when his brother Carlos, the field man of the duo, collected some more descriptions of the Yemisch from native people. It was indeed a large, amphibious mammal that sounded just like a giant ground sloth. They even had some bits of skin like those collected from Last Hope Inlet which they attributed to the animal. Clearly giant sloths were still roaming South America, and they were dangerous creatures indeed.

Newspapers in Argentina went crazy over the story. Not only had the continent's most eminent paleontologist confirmed the existence of living giant sloths but new sightings funneled their way into the press. The megatherium fever even stretched to England where some naturalists, like E. Ray Lankester, agreed that giant ground sloths may still survive in South America. It is not surprising then that some enterprising souls set out to catch the beast, but all ultimately returned empty handed. It seemed that those who went out looking for the Neomylodon were the least likely to find it.

Not everyone was convinced that giant ground sloths survived into the modern day, however, and some of Florentino's South American colleagues thought that his enthusiasm had superseded good judgment. To check the validity of Ameghino's claim the naturalist Rodolfo Hauthal went back to the Lost Hope Inlet cave to reexamine the evidence. His conslusions were just as startling as Ameghino's.

When Hauthal investigated the cave he found stone tools, hay, charcoal, plant fibers, sloth bones, and a pile of sloth dung several feet high. What could this all mean? Clearly humans and sloths had both used the cave, but Hauthal went a step further to suggest that they had been in the cave at the same time. Humans had held sloths in captivity and may have even domesticated them, Hauthal argued, and the Lost Hope Inlet cave had once been a giant sloth stable. For this reason the kind of extinct sloth represented by the scraps of skin and bones was renamed Grypotherium domesticum, the domestic ground sloth.


A restoration of the giant sloth Mylodon. [source]

(It is also noteworthy that Hauthal and colleagues re-named the animal said to terrify the native people. Based upon the evidence from folklore they renamed it Iemisch listai, a move that irritated some other scientists. In a review of the papers, for instance, the paleontologist J.B. Hatcher objected to 1) using a "barbarous" native word as a genus name, and 2) erecting a new genus and species on folklore.)

It seems that other authorities did not quite know what to make of Hauthal's hypothesis. It was often repeated in reviews and announcements but rarely did it receive further comment (at least in English-language publications). The author of To the River Plate and Back, William Jacob Holland, agreed but it seems that many others did not know how to handle the idea of domesticated giant sloths. Even the paleontologist A.S. Woodward, while skeptical, wanted to know more about this potential relationship between humans and ancient sloths.

In the end, though, the tale of the Yemisch seemed to unravel. J.B. Hatcher stated that he had never heard of such a creature during his time in South America and others suggested that the mythological creature was better understood as an amalgam of a giant river otter and a jaguar. It was entirely possible that the Ameghino brothers inflated what little they had heard from the native people and the newspapers ran with it once it hit the academic presses.

We should not be too hasty in saying that the Ameghinos created a story where there was none, however. Recall that Thomas Jefferson, on first sight of seeing the huge claws of the giant sloth Megalonyx, thought they belonged to an enormous tiger-like cat. If the native people of Patagonia did hold beliefs about the Yemisch it is entirely possible that their beliefs were reinforced by finding the plentiful remains of giant sloths. This one sounds like a case for a geomythologist.


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> that the mythological creature was better understood as an > amalgam of a giant river otter and a jaguar.

Or perhaps the leopard seal *Hydrurga*?

It's undoubtly fierce enough to inspire a few legends, and the seal theory might explain the fact that aquatic or semi-aquatic cryptid mammals are more or less a pan-gondwanan phenomenon:
SA has the Iemisch, Australia the Bunyip and New Zealand the Waitoreke (on the other hand, if waitorke really means "water animal with spurs", this strongly suggests that the creature in question is - or was - non-therian; but I don't speak Polynesian in general or Maori in peculiar, and can't guarantee for the correctness of this translation).

Great post!
Willy Ley's "The Lungfish, the Dodo and the Unicorn" contains a chapter about the same story. I think the skin is exhibited at the Berlin natural history museum. At least I remember seeing a ground sloth skin there that was labeled as being from Ultima Esperanza, and this placename was mentioned in Willy Ley's book.
I've once seen the idea seriously proposed that the "ground sloth" bones in the cave were actually from giants that kept the humans captive. This was in "Die Erde und unsere Ahnen" (The earth and our ancestors) by Ernst Betha (1913), definitely the craziest book I've ever seen.

By Lars Dietz (not verified) on 29 Apr 2009 #permalink

FWIW, it appears that there were ground slothes that lasted into historical times...on Cuba and Hispanola. The West didn't see them, but the introduced species have been fingered as the likely killers.

Will; I did not know that. Do you have a reference for that? I would be interested in checking that out.

Ameghino sometimes got carried away with ideas now thought off -- he thought humans were descended from New World primates -- but he was an important and serious scientist. So, if pieces of Mylodon skin came into his possession, they would have been preserved: they are probably still in the museum in Buenos Aires. Has a fragment been sacrificed by radio-carbon dating? I dimly recall reading that it had been established that the sloth remains from Argentina were actually a lot older than their fresh-seeming appearance had suggested, but don't remember any details.

By Allen Hazen (not verified) on 29 Apr 2009 #permalink


Do you have a reference for that? I would be interested in checking that out.

For recent estmates of extinction dates of both continental and Caribbean ground sloths, see Steadman et al. (2005). According to this study, the youngest known ground sloth remains (belonging to the species Neocnus comes) are from the island of Hispaniola and they are dated to circa 4400 years BP.

Incidentally, the Ultima Esperanza cave and its well-preserved ground sloth fossils were featured prominently in episode 11 of David Attenborough's classic Life on Earth series.


Steadman, D.W., Martin, P.S., MacPhee, R.D.E., Jull, A.J.T., McDonald, H.G., Woods, C.A., Iturralde-Vinent, M. & Hodgins, G.W.L. 2005. Asyncronous extinction of late Quaternary sloths on continents and islands. Proceedings of the National Academy of Sciences of the United States of America 102, 11763-11768.

Er... that should of course be 'Asynchronous', not 'Asyncronous' (and while I'm at it: 'estimates', not 'estmates').

> The West didn't see them, but the introduced species have
> been fingered as the likely killers.

I can't imagine that those pesky canids the Caribs or the Tainos (or whoever was living on the greater Antilles in pre-columbian days)kept were much of a danger to a ground sloth, even if it was a dwarved island form. I think those Carribean ground sloths were hunted to extinction by humans, like many island species were.

FWIW, it appears that there were ground slothes that lasted into historical times...on Cuba and Hispanola. The West didn't see them, but the introduced species have been fingered as the likely killers.

Nice story. I remember hearing about it as a kid (my aunt/godmother is a full prof in biology) but I doubt most people down there (don't live there anymore) know about it.

As a minor point of style, the adjective for somebody born in Argentina is Argentine and not Argentinian.

I enjoy your blog very much.

Do you have a reference for that?

Here's another reference:

A younger record from Cuba, a tooth of Megalocnus rodens dated to 4,190 yr BP.

MacPhee, R. D. E., M. A. Iturralde-Vinent & O. Jiménez Vázquez. 2007. Prehistoric sloth extinctions in Cuba: implications of a new "last" appearance date. Caribbean Journal of Science 43(1):94-98.
Free PDF here

From Puerto Rico, the other Greater Antillean island that was inhabited by sloths, there are no reliable last appearance date, for now.

Some months ago I was in Berlin and saw some of those ground sloth remains. It was really amazing how incredibly fresh they looked. There were several pieces of skin, a lot of dung and a half mandibula. All looked so fresh that you would NEVER suppose that they are many thousand years old. The mandibula for example was pure white in colour, and there were even dried remains of the gingiva attached around some of the teeth. If you look at human mummies, you will hardly ever find only one half as good presevered as this remains.

Only that the cave and region that you mention is not in Argentina but in southern Chile. It is called the "milodon's cave" and it lies a some kilometers to the north of Punta Arenas.

Now I'm less convinced of your post if you do not check some essential data as such.

Cristina; So what? I appreciate the correction, but I probably made the mistake because the original sources that I found relating to this story (see the links contained above) were vague as to the exact location of the cave. I wrote it so long ago that I cannot tell you exactly why I made the mistake, but the small mistake relating to the location of the cave does nothing to take away from the rest of the post. I honestly don't know what are are "less convinced" of now, especially since I did reference and link my sources.

The ground sloth skin is a prominent part of the story in Bruce Chatwin's "In Patagonia", where his relatives call it a "brontosaurus".
There are preserved pieces of skin also in the NHM, London and Zoological Museum, Amsterdam. It seems that the initially intact flayed pelt was cut into sections and divided amongst a number of institutions. There was also some remains of the hide of a ?horse found at UE as well.

By Ross Barnett (not verified) on 18 Jan 2011 #permalink

I saw something by this description early morning at a local park here in Bellingham, WA. a few years ago. Years prior in a another major park in Tacoma, WA. I saw it as well. Don't know what to make of it in either case, but I've never had any other "episodes" with giant furry sloth creatures! Just sharing...

By Rouillie Wilkerson (not verified) on 17 Apr 2011 #permalink

I saw something by this description early morning at a local park here in Bellingham, WA. a few years ago. Years prior in a another major park in Tacoma, WA. I saw it as well. Don't know what to make of it in either case, but I've never had any other "episodes" with giant furry sloth creatures! Just sharing.

This is a gross oversimplification that gives the impression that Scopes was a regular teacher at the schools and had actually taught evolution to his students. (At least, that's how I read such statements before I knew better.) The truth of the matter is that Scopes was a football coach and a substitute teacher, and Scopes himself was uncertain if he ever even covered the topic of evolution while acting as substitute for a science class. Why, then, was Scopes put on the stand?

In 1925 the Tennessee legislature passed the Butler Act which declared;

... that it shall be unlawful for any teacher in any of the Universities, Normals and all other public schools of the State which are supported in whole or in part by the public school funds of the State, to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.
As a reaction to this the ACLU offered to defend anyone who so dared to teach evolution in Tennessee, and some local business owners in Dayton thought that their town might be able to get some easy publicity if they were able to come up with someone who they could say violated the Butler Act. Scopes volunteered, and ultimately he was charged with teaching evolution to a high school class. (Scopes was arrested but not detained. ı am learn altın çilek market