The American incognitum and the History of Extinction Studies


Georges Cuvier (1769 -1832) and the painting of Charles Wilson Peale’s reconstruction of the American incognitum

Extinction is the ultimate fate of all species. More than 95% of all species that ever lived are now extinct. But prior to the 18th century, the idea that species could become extinct was not accepted. However, as the new science of paleontology began bringing its first major discoveries to light, researchers began to wonder if the large vertebrate fossils of strange creatures unearthed by the Enlightenment explorers were indeed the remains of extinct species.

In 1739, French soldiers under the command of Baron Charles le Moyne de Lougueuil recovered a tusk, femur, and three curious molar teeth from Big Bone Lick, Kentucky, a place known in several American Indian narratives. Lougueuil sent these specimens to the Cabinet du Roi (Royal Cabinet of Curiosities) in Paris. In 1762, Louis Jean-Marie Daubenton, a zoologist at the Jardin du Roi concluded that the femur and tusk from the Longueuil’s collection were those of a large elephant, the “Siberian Mammoth,” but the three molars came from a gigantic hippopotamus.

Molar collected at Big Bone Lick in 1739 and described in Paris in 1756. (Georges Cuvier, Recherches sur les ossemens fossiles)

By the early 18 century it was inconceivable for many researchers that a species could be vanished. Naturalist Georges-Louis Leclerc de Buffon, wrote in 1749 about the extinction of marine invertebrates, but he adopted Daubenton’s view that the Siberian mammoth and the animal of the Ohio, known as the American incognitum, were both northern forms of the extant elephant rather than a vanished species. British anatomist William Hunter was the first to speculate that these remains might be from an extinct species. In 1799, the discovery of an American incognitum femur from Quaternary deposits in the Hudson River Valley led to excavations organized by Charles Wilson Peale. In 1801, the excavations resulted in the recovery of an almost complete skeleton. Peale reconstructed the skeleton with help from the American anatomist Caspar Wistar, and the displayed the mounted skeleton in public in December of that year.

In 1806 Georges Cuvier resolved the controversy about the  American incognitum demonstrating that both the Siberian mammoth and the “animal de l’Ohio” were elephants, but of different species. He described the Ohio elephant as a mastodon and he reached the conclusion that probably represented an extinct species. Cuvier was also the first to suggested that periodic “revolutions” or catastrophes had befallen the Earth and wiped out a number of species. But, under the influence of Lyell’s uniformitarianism, Cuvier’s ideas were rejected as “poor science”. The modern study of mass extinction did not begin until the middle of the twentieth century. One of the most popular of that time was “Revolutions in the history of life” written by Norman Newell in 1967.



Macleod, N. The geological extinction record: History, data, biases, and testing. Geol. Soc. Am. Spec. Pap. 505, (2014), DOI: 10.1130/2014.2505(01)​

Marshall, Charles R., Five palaeobiological laws needed to understand the evolution of the living biota, Nature Ecology & Evolution 1, 0165 (2017), DOI: 10.1038/s41559-017-0165 .


A Brief Introduction to Conservation Paleobiology

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Richard Owen stands next to the largest of all moa, Dinornis maximus (now D. novaezealandiae). From Wikimedia Commons.

Over the past 50 years, the pace and magnitude of human-induced global changes has accelerated dramatically. The term defaunation was created to designate the declining of top predators and herbivores triggered by human activity, that results in a lack of agents that control the components of the ecosystems vegetation. Although anthropogenic climate change is playing a growing role, the primary drivers of modern extinctions seem to be habitat loss, human predation, and introduced species. The same drivers that contributed to ancient megafaunal and island extinctions.

The emerging discipline of conservation paleobiology is supplying necessary information to understand how ecosystems vary naturally through time and space and how they respond to major perturbations. The fossils that have provided such data include phytoplankton, zooplankton, fossil pollen, seeds, leaves, wood, invertebrate animals with hard parts, and vertebrate animals. They are particularly useful because they often show high fidelity to the living communities. Quaternary fossils have proven especially informative for addressing conservation questions, but useful information has also come from much older fossil deposits, reaching back millions of years.


Bison near a hot spring in Yellowstone National Park (From Wikimedia Commons).

The analytical methods that allow comparing present with past fall into two main categories: taxon-based and taxon-free. Taxon-based methods rely on the presence, absence, or abundances of certain taxa and their underlying diversity. Taxon-free methods use metrics that reflect ecosystem function rather than structure. Depending on the availability of fossils and the type of conservation question being asked, one or the other approach may be more appropriate.

Taxon-based paleontological data are critical in deciding if a “natural” landscape represents a historical or a novel ecosystem. Historical ecosystems are those that still have at least 70% of the habitats that were present 500 years ago and that contain fewer than 5 people/km2. In the world’s first national park, Yellowstone National Park, USA, paleontological data influenced critical management decisions by demonstrating that Yellowstone preserves a historical ecosystem. Fossil deposits verified that almost all of the mammal species that had occupied the region for millennia are still present. Also, palynological records show that the current vegetation has persisted with only minor fluctuations in abundance of dominant taxa for at least 8000 years.

Lyuba, the best preserved mammoth mummy in the world, at the Field Museum of Natural History (From Wikimedia Commons).

Lyuba, the best preserved mammoth mummy in the world, at the Field Museum of Natural History (From Wikimedia Commons).

Taxon-free paleontological can often be related to environmental parameters with statistical significance data, and are critical for understanding whether certain ecosystems are approaching “tipping points,” as demonstrated by analysis of diatoms, pollen, and sediments from lake cores.

Fossils have also figured prominently  with efforts to reconstruct copies of species that humans have driven to extinction either recently (passenger pigeons) or in the deeper past (mammoths). Unfortunately, the ecosystems that supported many extinct species no longer exist, so survival outside of captivity would be difficult. In addition, preventing the extinction of extant species and habitats numbering in the thousands already is challenging, so the prospects of sustaining “de-extincted” species are poor at best. Media reports are presenting de-extinction in an optimistic framework, and conveying the impression that we face a real possibility of bringing mammoth back from extinction in  the near future. Of course, this is far from truth. We will never be able to recreate most extinct species in their purest form. Ultimately,  genetic engineering to simulate extinct life also raises ethical and legal concerns.



Anthony D. Barnosky et al. Merging paleobiology with conservation biology to guide the future of terrestrial ecosystems. Science, 2017 DOI: 10.1126/science.aah4787

Rodolfo Dirzo et al., Defaunation in the Anthropocene, Science 345, 401 (2014); DOI: 10.1126/science.1251817

Braje, T.J., Erlandson, J.M., Human acceleration of animal and plant extinctions: A Late Pleistocene, Holocene, and Anthropocene continuum. Anthropocene (2013),

Richmond, D.J., Sinding, M-H.S., Gilbert, M.T.P. (2016). The potential and pitfalls of de-extinction. — Zoologica Scripta, 45, 2236DOI: 10.1111/zsc.12212