In a recent post, I mentioned the Diprothomo platensis, a hominin described by Florentino Ameghino (see his work online Le Diprothomo Platensis, (full title in French adds "A precursor of the Lower Pliocene man"), published in 1909 in Buenos Aires, in French.
I have mentioned this "hominin" in several posts over the years: Diprothomo and Lagoa Santa - Homo erectus? (2011) and more recently At the Buenos Aires Natural Sciences Museum (2025) where I got to see the skull.
Ameghino's book on the Diprothomo platensis
In his book he mentions how the upper part (calotte) of a skull was discovered during the construction of Buenos Aires' port, on the River Plate, at Dry Dock #1 on the north flank of the Darsena Norte (North Dock). Though built between 1887 and 1897, ths spot still exists even though the old port and docks have been recycled and revamped into a posh,expensive neighborhood (see Google map).
Ameghino stated that the skull came from the basal layer of the Pampean Formation of Pliocene age, 40 to 50 m thick (120 to 150 ft.), and that dips up to 20 m (60 ft) beneath the River Plate's water level. The lowest level was labeled "Pre-Ensenadan", 32 meters (66 feet) below ground surface.
Ameghino also added two plates with top views of a Pithecanthropus (now known as Homo erectus) and and a Neanderthal, shown below.
He included a lateral view of it (below) and remarked about it being more primitive (inferior) than the (already inferior) Neanderthal: "The famous Neanderthal skull, whose inferior characteristics have been greatly exaggerated, differs profoundly in its lateral view from that of Diprothomme and by characteristics that indicate a much more advanced evolution than that of the latter."
Below is a front view of the skull cap and the browridges.
Ameghino provided a reconstruction of the complete skull, as he imagined it, a primitive, small-brained, low forehead, hominin with prominent brow ridges:
In the article, he fitted the Diprothomo into his evolutionary sequence for the first humans, originating in South America, and from there, expanding across the globe. Ameghino believed that humans had evolved during the Tertiary Period (see my posts on his theory). His phylogenetic tree, outside of America places the Diprothomo as an ancestor of both modern humans and the parallel branch of Neanderthals, and regarding the Pithecanthropus, he states they are different genra, and points out the lack of metopic crest in the Diprothomo (no mention of the saggital crest) adding: "These are two divergent morphological lines, the one that leads to Pithecanthropus is completely extinct. Based on the bestialization characteristics it presents, I declared in 1906 that Pithecanthropus was not and was the ancestor of Man." Below is Ameghino's phylogenetic tree:
Notice the progression from the Tetraprothomo to the Triprothomo (leading to the pithecanthropus or Homo erectus), diprothomo, prothomo, and the Homo pampaens, that leads to modern Homo sapiens!
The final part of the book includes some photographs of the skull.
But this theory, and the findings went against the dogma set down by the American (for U.S.A) school of thought that proposed the Beringian route for an Old World human to reach America relatively recently (3,000 to 10,000 years ago). This cause was championed by Czech - American anthropologist Alex Hrdlicka and his team. After visiting Argentina in 1910, and inspecting the bones (of Diprothomo and other specimens) they harshly refuted Ameghino’s theory, ridiculing it and effectively killing it (see a summary published in Science, 1912). Hrdlicka's legacy lives on in the Clovis First theory (see my post on it).
In 1912 Hrdlicka, Holmes and Bailey Willis published through the Bureau of Ethnology of the Smithsonian Institution a report, "Early Man in America". They say that the skull was not found embedded in the sediments, but that it probably fell down, into the excavation site of the dry dock from more recent sediments. That the workers had been playing "bochas" (bowls) with the skull (page 320). But, reading the arguments put forward to discredit the site, I am not fully convinced that they are impartial or that Ameghino was wrong.
Then, the authors state that Ameghino aligned the skull incorrectly, and this led him to conclude it had a small brain and slanting forehead: "In a detailed study of the specimen it soon became plain that almost the entire original description by Ameghino had miscarried by reason of the fragment having been placed and considered in a wrong position." Below is an image depicting the "correct" (upright - Hrdlicka) and the "incorrect" (slanting - Ameghino) positions for the calotte:
The American team concluded that "The sum of the results of the writer's study of the Buenos Aires skull fragment, regardless of its uncertain history, is that the specimen fails utterly to reveal any evidence which would justify its classification as a representative of a species of ancient Primates, premediate forerunners of the human being, the Diprothomo. Every feature shows it to be a portion of the skull of man himself; it bears no evidence even of having belonged to an early or physically primitive man, but to a well-developed and physically modern-like human individual" Categorical rebuttal of Ameghino's claims.
A Modern view on the Diprothomo
Schávelzon, 2018 argues that Ameghino's skull is recent, and was brought by the potent current of the Paraná River downstream, ending up in the sediments in Buenos Aires, he also states that it dates back to 1720, without providing a source.
Politis and Bonomo, 2011, review Ameghino's findings and theories, and regarding Diprothomo, they offers two explanations: the one given by Bailey Willis, or as a second option, a hoax; and they don't blame it on Ameghino but on the ones who discovered the skull perhaps with the intention of selling it, a common practice in those days.
The dating of the skull mentioned in both papers is unpublished, and Politis and Bonomo gives the following account: "In 1997, José Bonaparte, then director of the Vertebrate Paleontology Section of the Bernardino Rivadavia Museum of Natural Sciences, where the skullcap is currently housed, sent a sample of it to the University of California, Riverside laboratory for AMS dating. The age reported by Taylor on April 22, 1998, is 230 ± 40 14C years BP (Table 1). In the report, Taylor notes that the rest of the bone was in suitable condition for radiocarbon dating: “The analysis was taken on the total amino acid fraction by ion exchange chromatography after chemical and physical cleaning of the bone surface to remove any adhering contamination. The amino acid profile indicated that the bone still retained a considerable amount of collagen.”"
Conclusions
Despite his mistakes (earnest ones), which we can excuse due to the lack of adequate dating tools, other than sedimentary references, Ameghino may have been onto something. He also suggested that samples of "tierra cocida" or baked earth were primitive ceramics produced by these ancient hominins. (See Podgorny, 2015 who also gives a good summary on the Diproghomo). Ameghino also noted the "eoliths" or very crude stone tools found in deep layers, which he believed were pre-Acheulean.
I will be posting about Ameghino in the near future.
Patagonian Monsters - Cryptozoology, Myths & legends in Patagonia Copyright 2009-2026 by Austin Whittall ©
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