Following my post on the possibility of Denisovans expanding their territory and moving east, into America, one of the followers of my blog, Marcelo Bruyere wrote a comment to the post, suggesting that old sites such as those that would correspond to a Pleistocene peopling of America before the last glacial period would have to be located beyond the area scoured by the glaciers of ice ages that followed their migration 400,000 years (400 ky) ago. Sites located in temperate regions would be safe from the destructive effects of the glacial ice fields.
Marcelo mentioned the Cerutti Mastodon site which is 130 ky old which is in California, 32°S as an example and suggested that South America would also be a great place to search for such sites, but not in caves or rock shelters, which are the favorite haunt of archaeologists looking for ancient campsites. Instead, he says, these sites should be sought "in other environments; such as possible relicts of ancient plains bearing rivers and/or lacustrine systems, that could comply with the condition of having been originally developed in terrains well deep into the Pleistocene" and continues, proposing the Argentine plains known as the Pampean region as a suitable place to look for this type of sites.
The Pampa Region
The Pampas, whose name comes from the Native American Quechua language and means "plain", is a vast expansion of flat prairies originally covered with native temperate grasslands, with a very slight west to east incline, spanning 1.2 million km2 (460,000 sq. mi.). The region is outlined with a red line in the map below:
Its western flank rises to about 200 meters (600 ft.) into an arid area with an open savanna-like region of "monte" and "espinal", with caldén trees, that then becomes even more drier as it blends into the Cuyo Andean Region, and the Northern Patagonia. The eastern part is more humid and is lower. Two ancient mountain ranges from the Precambrian and Paleozoic jut out of the lowlands in south-central Buenos Aires province, the Sierra de la Ventana which reach their maximum altitude with the Cerro Tres Picos (1,240 m - 4.066 ft) and the Tandil hills with 500 m (1,600 ft), these continue beneath the overlying silt, and form the basement on which the plains were formed during the Cenozoic period. Sediments originating in the Andes mountain range, were eroded and transported east by the wind (aeolian) and rivers (fluvial) and deposited on the granite bedrock over the past 12 million years (Zárate & Folguera, 2009).
Of the different cycles of sedimentation, the one we are interested in is the third one, which took place during the "...late Pliocene-late Pleistocene circa 3.2 Ma- 0.040/0.030 Ma [it] includes deposits bearing Marplatan, Ensenadan and Bonaerian fossil remains. They are distributed in the Salado tectonic basin, forming the bedrock in which fluvial valleys are excavated." Zárate & Folguera, 2009. Marcelo points out that the "undulating" Pampa, which is an area located in the northeastern corner of Buenos Aires province, with low-lying hillocks (a "gently rolling landscape" (Zárate, 2002) that break the flat plains " is a particularly good example of a suitable one for this purpose because; a) it overlies a massive (30 meters thick) Pleistocene substrate whose geological record goes all the way down (although with hiatus) from 12/13 Ka to the vicinities of Matuyama/Gauss boundary (ca. 2,58 Ma), b) it is crossed by many rivers whose valleys are deeply incised into this substrate, and c) also presents some relict landscapes outcropping subaerially (albeit, conditionally accessible), whose geological levels are within Matuyama magnetic ages (>0.78 Ma)."
This region has produced many megafaunal fossils and also human remains corresponding to Paleoindians. To clarify the text, the Matuyama boundary is a period that lasted from 2.59 to 0.78 Ma and marked a reversal of the Earth's magnetic field. During this time, a compass wouldn't have pointed north, it would have pointed south. Point c) mentions that some of the deeper layers are accessible in this region, on the surface, exposed ("Subaerial").
It was in the banks of the rivers that cut across the plains, that the first megafaunal fossils were recovered during the late 18th century and sent back to Spain from the Colonial Buenos Aires: the Megatherium americanum described by Cuvier in 1796. These were considered antediluvian creatures. The banks of these rivers still provide fossils (Scanferla, 2013, Chichkoyan, 2022).
The mid Pleistocene sediments are not that deep. For instance Tófalo, 2011 reports "Present day soil is found at the top of the section. Its parental material was sampled at 1.2 m [4 ft] where an OSL dating yielded an age of 30 ± 4 kyr. Another OSL age >126 ± 10 kyr for a sample taken at 7.3 m [24 ft]" Sediments that could potentially contain Denisovan or erectus remains would be at that depth.
Interestingly, current research has looked into these locations and found old pre-Clovis tools dated to 30 to 40 ky ago. See Marcelo Toledo, 2017, whom I quote below. Toledo reported finding a flint tool that "was unambiguous as well as embedded into basal sand of the Red Luján sequence (a geological sedimentary layer), which have been dated between 25 and 30 ky BP... These preliminary results prove human presence towards 25-30 ky BP in the Luján valley." These tools are obviously man-made because there are no sources of stone or rocks nearby (these plains span hundreds of kilometers, and the nearest rock sources are over 200 km away (125 mi) and couldn't have reached this area in any other way other than by human transportation.
Eoliths
One hundred and forty years ago, Florentino Ameghino, who proposed an autochthonous origin, in America, for humans, who then migrated across the globe (one of these ancient human specimens was the Diprothomo platensis) supported his theory with fossils and early, cobble-styled tools that he had found similar tools along the Lujan River banks, and also bones of megafaunal animals that bore clear stone cut marks.
Ameghino called these primitive tools "eolithic" (Greek for "dawn stones"), refraining from using the term "paleolithic" because they differed substantially from the Acheulean industry found in Paleolithic Europe. These stones were old, and different as you can see in the following image:
And these sites are just scraping the surface, the most recent sedimentary layers, below are more, reaching down to almost 1 million years.
The idea that hominin remains from 50,000 to 800,000 years ago may be buried by tens of meters of silt in these open plains is exciting, and as we have seen, some proof has already been discovered.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall ©
