Rosa Rubicondior: Refuting Creationism - The Slow Evolution and Extinction Of African Megafauna

A selection of extinct African megaherbivores

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Scarce emergence of new species drove the decline of African megaherbivores | Museo Nacional de Ciencias Naturales

Africa’s elephants, rhinoceroses and hippopotamuses are surviving representatives of a much richer assemblage of giant herbivores that once included such animals as Deinotherium, an elephant relative with downward-curving tusks, and the pig-like anthracotheres, relatives of modern hippopotamuses. These animals were not merely conspicuous members of their ecosystems. As “ecosystem engineers”, megaherbivores—here defined as herbivorous mammals weighing at least one tonne—alter vegetation, disperse seeds, open pathways, create water holes and redistribute nutrients.

Why so much of this diversity disappeared has usually been approached as a question of extinction. Large animals reproduce slowly, require extensive habitats and comparatively large quantities of food, so it seems intuitively reasonable to assume that they must have been especially vulnerable when climates and environments changed. Human hunting has also figured prominently in explanations of the much more recent global disappearance of large mammals.

But the diversity of any group depends upon two processes, not one. Extinction removes species, while speciation produces new ones. Even a lineage with a comparatively modest extinction rate will decline if its species disappear faster than evolutionary divergence can replace them. Conversely, a group can withstand relatively frequent extinctions if new species continue to arise sufficiently rapidly.

A new study published open access in Nature Communications. has now examined both sides of that evolutionary balance. Juan L. Cantalapiedra and colleagues analysed 3,327 African fossil occurrences representing 396 species of herbivorous mammals. Using neural-network models, they reconstructed changes in speciation and extinction over the past 23 million years while considering body size, tooth-crown height, evolutionary relationships and environmental change. Their results challenge the apparently obvious assumption that Africa’s largest herbivores declined because they were inherently more prone to extinction.

In fact, the models indicate that extinction rates were generally somewhat lower among the largest species. High-crowned teeth, which better withstand abrasive diets, were also associated with a reduced risk of extinction. The underlying problem for megaherbivores was that their already low speciation rates could not compensate for the species that were lost.

The imbalance developed over millions of years. As Africa became increasingly arid from about 7.2 million years ago, both speciation and extinction initially accelerated as changing vegetation and expanding open habitats reorganised its ungulate communities. Speciation then levelled off after about 3.6 million years, while extinction continued to rise and increased sharply with the beginning of the Pleistocene, about 2.58 million years ago. During the driest intervals, smaller herbivores generated new species at substantially higher rates, whereas speciation among megaherbivores was suppressed still further. The resulting decline was already well under way long before humans possessed the technology needed to hunt such enormous animals systematically.

This does not mean that humans played no part in the most recent losses, nor that climate alone explains every extinction. Rather, it places recent events within a much longer evolutionary history in which changing climate, declining ecosystem productivity, extinction and unequal rates of speciation gradually transformed the African fauna.

Africa’s Lost Giants—and Why Evolutionary Success Is More Than Survival. Modern Africa retains more megaherbivores than any other continent, but elephants, rhinoceroses and hippopotamuses are the survivors of a formerly much richer community of enormous plant-eating mammals.

Among the vanished forms were:

Deinotherium — a huge, distantly related cousin of modern elephants, distinguished by a pair of downward-curving tusks attached to its lower jaw.
Anthracotheres — a diverse family of semiaquatic, often pig-like even-toed ungulates related to the lineage that produced modern hippopotamuses.
Extinct giant giraffids — relatives of giraffes and okapis, some with massive bodies and elaborate horn-like ossicones.

These animals lived within ecosystems that were repeatedly transformed as Africa became cooler, drier and more seasonal. Forests contracted in many regions, open woodland and grassland expanded, and changing vegetation created new ecological opportunities for some herbivores while reducing them for others.

A simplified timeline

23 million years ago: The interval examined by the researchers begins, close to the start of the Miocene Epoch.
About 7.2 million years ago: Increasing aridity begins to reorganise African vegetation and ungulate communities. Both speciation and extinction accelerate.
About 3.6 million years ago: The production of new herbivore species levels off, while species continue to disappear.
2.58 million years ago: The Pleistocene begins. Extinction rates rise sharply and diversity declines across several herbivore groups.
Much later: Hunting, habitat alteration and other human activities add further pressures, but cannot explain a decline already under way millions of years earlier.

Why might very large animals produce new species slowly?

New species usually arise when populations become separated and accumulate genetic, anatomical or behavioural differences. Megaherbivores tend to have long generation times, low reproductive rates and comparatively small populations spread across extensive ranges. These characteristics can limit how quickly isolated populations diverge into distinct species.

The new study identifies low speciation as the principal imbalance behind the megaherbivore decline, although it does not suggest that a single biological mechanism accounts for every lineage. Climate, geography, ecology and the particular history of each group would all have influenced whether populations divided and evolved independently.

More than “survival of the fittest”

“Survival of the fittest” is an inadequate summary of evolution because the history of a lineage is not determined solely by how well its existing species survive. Long-term diversity reflects the balance between two processes:

Change in diversity = speciation - extinction.

A group can withstand frequent extinctions if it produces new species even faster. Conversely, a group whose members are individually resilient can still undergo a prolonged decline if too few new species arise to replace those that disappear.

Africa’s megaherbivores were not necessarily evolutionarily “inferior” or unusually prone to extinction. Their surviving species remain extraordinarily successful animals. Their collective decline occurred because environmental change continued to remove species while their slowly branching lineages failed to replace them at a comparable rate.

There is no trace here of the abrupt destruction and indiscriminate burial demanded by creationist Flood mythology. Instead, thousands of fossils distributed through rocks spanning 23 million years record successive communities responding to long-term environmental change. Some lineages disappeared, others diversified and the largest herbivores slowly lost ground because evolution failed to replace their losses quickly enough. It is a history of populations diverging and ecosystems changing—not a collection of animals created simultaneously and then catastrophically drowned a few thousand years ago.

The Spanish National Museum of Natural Sciences summarises the findings in its accompanying press release.

Scarce emergence of new species drove the decline of African megaherbivores

A study involving the MNCN-CSIC reconstructs the evolution of Africa’s large herbivores over 23 million years using more than 3,000 fossil records
The results show that, contrary to what was previously thought, these animals did not suffer greater extinction than smaller species

A study by the National Museum of Natural Sciences (MNCN-CSIC), the National Research Center on Human Evolution (CENIEH) and the University of Alcalá offers a new explanation for the decline of African megaherbivores. These animals, weighing more than a tonne and today including elephants and hippopotamuses, are known for acting as ecosystem engineers. The results, published in Nature Communications, reveal that their loss of diversity throughout history was not due to their being more vulnerable to extinction, as had previously been proposed, but rather that their decline was driven by particularly low rates of speciation —the emergence of new species.

To reach this conclusion, the team reconstructed the evolutionary dynamics of herbivorous mammals (hippopotamuses, antelopes and giraffes, among others) over the past 23 million years by analyzing 3,327 fossil records covering 396 species. The model incorporated data on body mass, tooth crown height, evolutionary relationships among families, and the environmental changes the continent has undergone.

An increasingly arid ecosystem

Around 7.2 million years ago, Africa’s climate began to grow drier, driving changes in landscapes and vegetation types that led to a reconfiguration of ungulate communities –hoofed mammals–. At the start of this phase, both the emergence of new species and the disappearance of others increased. However, 3.6 million years ago new species stopped emerging at the same pace, while extinctions kept rising and accelerated at the onset of the Pleistocene, 2.58 million years ago. These data show that the loss of diversity among large-bodied animals was already noticeable long before humans had the technological capacity to hunt animals of that size.

Species affected by this decline include Deinotherium, an extinct relative of elephants distinguished by its downward-curving tusks, and the Anthracotheriidae, animals related to hippopotamuses that resembled a large pig.

We found that, contrary to what was previously thought, larger species did not go extinct faster than smaller ones. In fact, their extinction rates were somewhat lower. The key is that megaherbivore species gave rise to new species much more slowly.

Juan López Cantalapiedra, lead author
Departamento de Paleobiología
Museo Nacional de Ciencias Naturales (MNCN-CSIC)
Madrid, Spain.

During periods of peak aridity, animals under 45 kilograms went extinct only 15% faster than those over a tonne, but generated new species at a rate 2.2 times higher.

This difference allowed small and medium-sized herbivores to better offset their losses. Large lineages, by contrast, kept losing diversity because not enough new species emerged to replace those that disappeared. This, combined with aridification, compounded the imbalance: it favored the emergence of new species among smaller ungulates while reducing it by nearly 20% among megaherbivores.

Óscar Sanisidro, co-author
GloCEE, Departamento de Ciencias de la Vida
Universidad de Alcalá
Alcalá de Henares, Spain.

The expansion of open habitats, increasing aridity, and declining ecosystem productivity transformed African communities over millions of years. Our results suggest that, although human activity may have contributed to some recent disappearances, it was not the main cause of the widespread loss of these large herbivores.

Ignacio A. Lazagabaster, co-author
Centro Nacional de Investigación sobre la Evolución Humana (CENIEH)
Burgos, Spain.

Publication:
Cantalapiedra, J.L., Lazagabaster, I.A., Blanco, F. et al.
Lower speciation, not higher extinction, drove African megaherbivore diversity collapse.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-76105-2

Abstract
Today’s ecosystems are severely depleted in megaherbivores (≥ 1000 kg) and lack many of the ecological functions once provided by these landscape engineers. Whether attributed to humans or climate, prevailing views of megaherbivore decline have focused on size-biased extinction (i.e., higher extinction rates among the largest species) while neglecting the role of speciation rates. To fully contextualize the decline of African megaherbivores, we examine 23 million years (Myrs) of African ungulate diversification using neural network models. Starting around 7.2 million years ago (Ma), African ungulate faunas witnessed overall accelerations in speciation and extinction rates. While speciation plateaued after 3.6 Ma, extinction rates increased sharply at the onset of the Pleistocene (2.58 Ma), leading to widespread diversity losses across herbivore guilds. Yet, we find that extinction rates are intrinsically lower in large-size lineages and in larger species within families. High-crowned dentitions, which last longer under hard, abrasive diets, are also associated with a suppression of extinction rates. Importantly, speciation rates in the largest herbivores are intrinsically low, and in some lineages were suppressed in response to increasing aridification during the last 5 Myrs. Our findings highlight the macroevolutionary complexity behind megaherbivore decline, advancing understanding of biotic crises involving large-bodied taxa.

Cantalapiedra, J.L., Lazagabaster, I.A., Blanco, F. et al.
Lower speciation, not higher extinction, drove African megaherbivore diversity collapse.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-76105-2

Copyright: © 2026 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

What emerges from this study is not a simplistic story in which the largest or supposedly least “fit” animals were the first to disappear. Africa’s megaherbivores were not unusually vulnerable to extinction; in several comparisons, their extinction rates were lower than those of smaller herbivores. Their long decline occurred because their lineages produced new species too slowly to replace those lost as environments changed.

This distinction exposes the inadequacy of reducing evolution to the slogan “survival of the fittest”. Evolutionary history depends not only upon whether existing species survive, but also upon whether populations divide, diverge and produce new species. Smaller herbivores could compensate for losses through more rapid speciation. The giant species, with their slower evolutionary turnover, gradually accumulated a deficit from which their diversity never recovered.

Nor was any of this planned. Natural selection has no foresight: it favours characteristics that confer an advantage under existing conditions, without anticipating what conditions might prevail millions of years later. Large body size could provide protection from predators, access to otherwise unavailable food and greater resilience during short-term hardship. High-crowned teeth could prolong survival on increasingly abrasive vegetation. Those immediate advantages explain how giant herbivores could evolve and prosper; they did not provide insurance against every future environmental change.

Evolution therefore produced increasingly specialised, often enormous animals without making provision for the changing world their descendants would inherit. They were not predestined to become extinct merely because they were large—indeed, the study found that their extinction rates were comparatively low—but their lineages generated replacements too slowly. When increasing aridity, expanding open habitats and falling ecosystem productivity continued to remove species, there was no intelligence overseeing the process, no mechanism preserving successful designs and no plan ensuring that each loss would be replaced.

The fossil record documents this unplanned history unfolding through successive climatic and ecological changes over millions of years. Human activity may have contributed to some recent disappearances, but it cannot explain a decline already established deep in the Pliocene and rooted in events beginning millions of years earlier. Still less can a single recent global flood explain a time-ordered succession of faunas in which speciation and extinction varied systematically with body size, dental adaptations and environmental change.

Africa’s surviving elephants, rhinoceroses and hippopotamuses are consequently not unchanged exhibits from an original creation. They are the remaining branches of a once much richer evolutionary radiation, shaped by immediate advantages, historical accidents and changing environments. Evolution had no destination in mind and no concern for the eventual outcome. When circumstances changed and speciation failed to keep pace with extinction, diversity simply dwindled—exactly as we should expect from an unguided natural process, and not from the foresighted work of an intelligent designer.

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