Most megafaunal herbivores in the Americas went extinct around 10,000 years ago, presumably disrupting the long-distance seed dispersal of large, fleshy-fruited plant species. Proposed in 1982, the neotropical anachronism hypothesis suggests that large fruits evolved to attract now-extinct megafauna. While this explains many key adaptations of ‘megafaunal fruit’ plants, it lacks robust evidence. In new research, researchers from Chile, Spain and Brazil discovered fossil evidence for frugivory in an extinct South American proboscidean called Notiomastodon platensis, and found that the disappearance of this animal and its relatives increased the extinction risks for megafaunal fruit plants in regions across South America.
Diversity of extinct mammals that inhabited the surroundings of Lake Tagua Tagua, Chile. Image credit: Mauricio Álvarez.
“In 1982, biologist Daniel Janzen and paleontologist Paul Martin proposed a revolutionary idea: many tropical plants developed large, sweet, and colorful fruits to attract large animals — such as mastodons, native horses, or giant ground sloths — that would serve as seed dispersers,” said Dr. Erwin González-Guarda, a paleontologist at the University of O’Higgins and IPHES-CERCA, and his colleagues.
“Known as the neotropical anachronisms hypothesis, this theory remained unconfirmed for over forty years.”
“Our study provides direct fossil evidence that confirms it.”
In the study, Dr. González-Guarda and co-authors analyzed 96 fossil teeth of the South American Pleistocene mastodon Notiomastodon platensis.
The fossils were collected over a span of more than 1,500 km, from Los Vilos to Chiloé Island in southern Chile.
Nearly half of the specimens came from the emblematic site of Lake Tagua Tagua, an ancient lake basin rich in Pleistocene fauna, located in the present-day O’Higgins region.
“To understand the lifestyle of Notiomastodon platensis, we employed various techniques: isotopic analysis, microscopic dental wear studies, and fossil calculus analysis,” the authors said.
“We found starch residues and plant tissues typical of fleshy fruits, such as those of the Chilean palm (Jubaea chilensis),” added Professor Florent Rivals, a researcher at ICREA, IPHES-CERCA and the Universitat Rovira i Virgili.
“This directly confirms that these animals frequently consumed fruit and played a role in forest regeneration.”
“Through stable isotope analysis, we were able to reconstruct the animals’ environment and diet with great precision,” said Dr. Iván Ramírez-Pedraza, a researcher at IPHES-CERCA and the Universitat Rovira i Virgili.
“The data point to a forested ecosystem rich in fruit resources, where mastodons traveled long distances and dispersed seeds along the way. That ecological function remains unreplaced.”
“Dental chemistry gives us a direct window into the past,” said Dr. Carlos Tornero, a researcher at IPHES-CERCA and the Autonomous University of Barcelona.
“By combining different lines of evidence, we’ve been able to robustly confirm their frugivory and the key role they played in these ecosystems.”
The researchers also applied a machine learning model to compare the current conservation status of megafauna-dependent plants across different South American regions.
Their results are alarming: in central Chile, 40% of these species are now threatened — a rate four times higher than in tropical regions where animals such as tapirs or monkeys still act as alternative seed dispersers.
“Where that ecological relationship between plants and animals has been entirely severed, the consequences remain visible even thousands of years later,” said Dr. Andrea Loayza, a researcher at the Instituto de Ecología y Biodiversidad.
“Species like the gomortega (Gomortega keule), the Chilean palm, and the monkey puzzle tree (Araucaria araucana) now survive in small, fragmented populations with low genetic diversity.”
“They are living remnants of an extinct interaction.”
The findings were publsihed today in the journal Nature Ecology & Evolution.
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E. González-Guarda et al. Fossil evidence of proboscidean frugivory and its lasting impact on South American ecosystems. Nat Ecol Evol, published online June 13, 2025; doi: 10.1038/s41559-025-02713-8
