Columbian Mammoths, Mammuthus colimbi with other Ice Age mammals.
Beth Zaiken
An open access paper published in Biology Letters by an international team of palaeontologists, led by Marianne Dehasque of the Department of Organismal Biology, Uppsala University, Sweden, will no doubt bring joy to creationists who prefer to see the world in simple black-and-white terms. It shows that one of the usual definitions of species—a group that can reproduce only with one another—needs revising. The paper reports that the two North American species of mammoth—the northern woolly mammoth (Mammuthus primigenius) and the southern Columbian mammoth (M. columbi)—regularly interbred where their ranges overlapped, and that the offspring were fertile.
In the black-and-white, science-vs-creationism world of creationist thinking, this will be taken to mean that if science is wrong, then creationism must be right, by default.
Creationist joy will be short-lived, however, once they realise that this interbreeding took place long before they believe Earth was created, and that the researchers explain the findings in terms of how mammoths evolved and diversified. Indeed, the evidence supports the theory that the Columbian mammoth itself evolved from a hybrid population—one of the mechanisms of evolution that creationist dogma insists does not occur. Not only is there not the slightest hint that biologists are abandoning the Theory of Evolution (ToE) in favour of creationism—as creationist leaders have claimed for at least half a century—but the ToE is used to explain the observable facts, and it does so with consummate ease.
Evolution and Diversification of Mammoths.The research and its significance are also explained in a Natural History Museum (London) Science News article by James Ashworth.
- Origins: Mammoths belong to the elephant family (Elephantidae) and first appeared in Africa about 5 million years ago, descending from early elephant relatives such as Primelephas.
- Spread and Adaptation: Mammoths dispersed into Eurasia around 3–4 million years ago, adapting to a wide range of environments from temperate forests to cold steppe-tundra.
- Key Species:
- Mammuthus meridionalis (Southern mammoth): Appeared about 2.5 million years ago, a large species adapted to relatively mild climates.
- M. trogontherii (Steppe mammoth): Emerged about 1 million years ago in Eurasia, giving rise to later lineages.
- M. columbi (Columbian mammoth): Migrated into North America and thrived in warmer southern regions.
- M. primigenius (Woolly mammoth): Evolved around 400,000 years ago, perfectly adapted to Ice Age conditions with long hair, fat insulation, and smaller ears to conserve heat.
- Hybridisation: Evidence now suggests that the Columbian mammoth may have arisen through hybridisation between woolly mammoths and earlier populations—illustrating how interbreeding helped shape mammoth diversity.
- Extinction: Most mammoth populations disappeared at the end of the last Ice Age (about 10,000 years ago), although small groups survived on Wrangel Island until around 4,000 years ago.
Hybrid mammoths roamed North America following interspecies breeding
North America’s mammoth species were breeding together within the past 40,000 years.
Fossil teeth found in Canada show that Columbian and woolly mammoths regularly had calves together where the different species mixed.
North America’s mammoth species weren’t as separate as they first appear.
Two different mammoths lived on the continent during the last Ice Age – the woolly mammoth in what is now Canada and the northern USA, and the Columbian mammoth further south. Adapted to different climates and food sources, it was assumed that these species lived largely independent lives.
Two mammoth molars found in western Canada, however, tell a different story. Genetic analysis of the fossilised teeth shows that they belonged to mammoths that were hybrids between the species.
In fact, because the younger fossil has more Columbian mammoth DNA than the other, Columbian and woolly mammoths must have bred many times over thousands of years. Professor Adrian Lister, one of our scientists who co-authored the new research, says that it suggests that hybrids play a much bigger role in evolution than was previously thought.
Traditionally, we’re taught that different species can’t breed together. As our ability to investigate genetics has developed, however, we’re finding that this has actually happened many times. The approach we’ve taken to investigate these mammoths could potentially be applied to other extinct animals as well. By reconstructing their history, we’ll be better able to see the role that hybridisation has played in the evolution of the species we see today.
Professor Adrian Lister, co-author.
Natural History Museum
London, UK.
The findings of the study were published in the journal Biology Letters.
The Columbian mammoth lived in warmer areas of North America, so is believed to have been much less hairy than the woolly mammoth.© The Trustees of the Natural History Museum, London
How did hybrid mammoths evolve?
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Part of the research team first uncovered evidence of mammoth hybrids back in 2021, when they extracted 1.2-million-year-old DNA from a steppe mammoth tooth found in Krestovka, Siberia.
Historically, steppe mammoths were thought to have evolved into the woolly mammoth in Eurasia around 700,000 years ago, and the Columbian mammoth in central and southern North America around 300,000 years later. However, the Krestovka tooth showed that the story isn’t quite that simple.
The Krestovka lineage turned out to be a distinct group of steppe mammoths whose members bred with woolly mammoths. It’s now thought that this hybridisation event is what created the Columbian mammoth. This interbreeding likely happened in North America after the woolly and steppe mammoths crossed a now-submerged land bridge between Siberia and Alaska.
As a result, as much as half of the DNA of Columbian mammoths was inherited from the woolly mammoths. But this new study shows that some woolly mammoths were also inheriting Columbian mammoth genetics.
One of the newly unearthed woolly mammoth teeth, dating from around 36,000 years ago, shows that the animal it belonged to inherited over 21% of its genome from Columbian mammoths. In the younger tooth, from around 11,000 years later, Columbian mammoths are responsible for just under 35% of the mammoth’s ancestry.
The increased level of Columbian mammoth DNA suggests that interbreeding between woolly and Columbian mammoths continued for thousands of years. Analysis of the sex chromosomes suggests that these encounters were mostly male Columbian mammoths breeding with female woolly mammoths.
The mixing of both species also made the North American woolly mammoths more genetically diverse than any other population known so far. Species with greater variety in their DNA are normally better able to adapt to changes, so it’s possible that this could have helped these mammoths to survive.
By examining the shape of two mammoth teeth and the DNA they contained, the team found evidence of Columbian and woolly mammoth hybridisation.© Laura Termes.
While these hybrid mammoths are genetically distinct from other members of their species, their teeth are surprisingly similar to other woolly mammoths. Adrian explains that this is likely the result of natural selection.
We tend to think that hybrids average out, so if a long animal bred with a short animal they’d have a medium-length offspring. So, in these hybrids, we might expect their teeth to have elements from woolly and Columbian mammoths. Instead, we found that their teeth are still very like those of woolly mammoths, which are well-adapted to eating grasses on cold, open plains. As the hybrids live in a similar environment, there’s a pressure for them to keep their woolly mammoth-like teeth.
Professor Adrian Lister.
It would have been similar for hybrid Columbian mammoths living further south. As they lived in a warmer environment with a wider range of foods, there was a pressure for these animals to keep their more generalist teeth despite having significant amounts of woolly mammoth DNA.
Studying the impacts of mammoth hybridisation further could also help protect living animals. Species such as the Scottish wildcat, for example, are in danger of going extinct because of breeding with closely related domestic cats. Having past examples for conservationists to draw on can help them to understand potential outcomes for at-risk species.
The changing conditions of the Ice Age also help scientists to understand how modern elephants, and other animals, might adapt to modern climate change.
Publication:Understanding how species can mitigate environmental change is very important at the moment, and we can look to past climate change to help with that. We know that mammoths ultimately didn’t survive the end of the Ice Age, and delving into their adaptability could help us better understand why.
Professor Adrian Lister.
Genomic and morphological analysis reveals long-term mammoth hybridization in British Columbia, CanadaOnce again, what at first sight might look like a problem for evolutionary biology turns out, on closer inspection, to be yet another confirmation of it. The discovery that woolly and Columbian mammoths could interbreed, and that hybridisation itself may have played a key role in the emergence of new lineages, fits comfortably within the explanatory power of the Theory of Evolution. Far from undermining it, such findings broaden our understanding of the many routes by which evolution operates.
Marianne Dehasque, Tom van der Valk, J. Camilo Chacón-Duque, Laura Termes, Petter Larsson, Hannah M. Moots, Florentine Tubbesing, Juliana Larsdotter, Gonzalo Oteo-García, Kelsey Moreland, Hans van Essen, Victoria Arbour, Grant Keddie, Michael P. Richards, David Díez-del-Molino, Peter D. Heintzman, Adrian Lister and Love Dalén
Abstract
Climate changes profoundly impact species distributions and can drastically alter dynamics between formerly isolated taxa. The evolution of mammoths within North America was characterized by repeated cycles of dispersal and putative gene flow between woolly and Columbian mammoths. However, as genome-wide studies on mammoths have predominantly focused on Siberia, the consequences of these North American range shifts remain unclear. Here, we generated genome-wide and morphological data for two Late Pleistocene mammoth molars from British Columbia, Canada (BC), and jointly analysed these with previously published data. Our genome-wide analysis (n = 16) revealed gene flow between woolly and Columbian mammoths that would have gone undiscovered based on morphological (n = 48) and mitochondrial analysis (n = 124) alone. Consistent with their hybrid nature, our analyses suggest that these two BC mammoths had elevated genomic diversity. Our results highlight the importance of combining data types to reconstruct past evolutionary events. These findings demonstrate how the geographical range expansion of woolly mammoths resulted in long-term hybridization with local Columbian mammoths and enhance our understanding of the genomic and morphological consequences of climate-mediated dispersal.
1. Introduction
The study of macroevolutionary processes in the fossil record has traditionally been based on inferences from morphological analysis [1]. The distribution and features of fossils provide insights into the ecology, evolution and dispersal of organisms, offering a glimpse into the history of life on Earth. Nevertheless, several factors, such as taphonomic biases, convergent evolution and cryptic biodiversity, may hamper inferences from morphology alone. Palaeogenomic methods and the growing availability of ancient DNA datasets now offer complementary tools to reconstruct past evolutionary processes [2–5].
The mammoth lineage (Mammuthus spp.) exemplifies how combining palaeontology and palaeogenomics can enhance our understanding of long-term evolutionary dynamics [6,7]. Traditionally, the classification of mammoth species is based on molar morphology, with more steppe-adapted lineages exhibiting a higher number of enamel lamellae and greater relative crown height, reflecting dietary changes over time and across geographical regions [8,9]. Recognized mammoth species that lived during the Pleistocene include the southern mammoth (M. meridionalis, Early Pleistocene), the steppe mammoth (M. trogontherii, late Early to Middle Pleistocene), the woolly mammoth (M. primigenius, Middle Pleistocene to Holocene) and the Columbian mammoth (M. columbi, Middle to Late Pleistocene).
Within Eurasia, the steppe mammoth evolved from a southern mammoth ancestor ca 1.8 million years ago (Myr). The steppe mammoth subsequently gave rise to the woolly mammoth around 700 thousand years ago (ka). In contrast, the evolution of North American mammoths began between 1.5 and 1.3 Myr, when mammoths with steppe-like morphology first crossed the Bering Land Bridge [9–11]. Fossil evidence traditionally suggested that Columbian mammoths were solely descended from this mammoth lineage [9]. However, ancient DNA analysis has revealed that they instead arose through a hybridization event that occurred ca 420 ka between woolly mammoths and a steppe mammoth population that descended from a distinct trogontherii-like lineage named Krestovka [6]. Notably, this resulted in all Columbian mammoth mitochondrial diversity nested within that of woolly mammoths [12–14]. Furthermore, gene flow between North American woolly mammoths and Columbian mammoths during the Late Pleistocene has also been suggested by the presence of intermediate molar morphologies [12,15,16].
Despite the evolution of mammoths within North America being a highly dynamic process characterized by repeated cycles of dispersal and putative gene flow [6,7,9,12,14], relatively little is known about the temporal continuity and extent of interbreeding between nominal woolly and Columbian mammoth species [17]. Here, we analysed two mammoth molars from British Columbia, Canada (hereafter ‘BC mammoths’), and explored their evolutionary affinities to Siberian and North American mammoths.
Figure 1. Molar morphology. (A) Bivariate plot of lamella number versus lamella length index for upper third molars of a comparative dataset of Mammuthus spp. (see electronic supplementary material, S2, for more details) and molar BC35.9k (RBCM.P997). (B) Lateral and (C) occlusal views of M3 of BC35.9k. (D) Occlusal, (E) lateral, (F) posterior and (G) anterior views of M3 fragment BC25.3k (AA.71.255.1). In (D) and (E) anterior is to the left. Scale bar (B–G) 100 mm.
Figure 2. Bayesian mitochondrial phylogenetic tree with BEAST. The colour of the tip names represents the geographical region with blue = North America, yellow = Europe, and purple = Asia, with tip names representing sample IDs (see electronic supplementary material, table S2, for corresponding accession numbers). The morphological species assignments are provided as colour bars on the right with brown = Columbian mammoth, orange = woolly mammoth, and grey = unidentified. The sample localities are plotted with jitter in the globe. North American samples for which genome-wide data that is available are coloured in dark red dots (woolly mammoths) and a triangle (Columbian mammoth). The scale bar represents evolutionary rate in years. The Asian elephant outgroup samples were removed from the figure for clarity.Dehasque Marianne, van der Valk Tom, Chacón-Duque J. Camilo, Termes Laura, Larsson Petter, Moots Hannah M., Tubbesing Florentine, Larsdotter Juliana, Oteo-García Gonzalo, Moreland Kelsey, van Essen Hans, Arbour Victoria, Keddie Grant, Richards Michael P., Díez-del-Molino David, Heintzman Peter D., Lister Adrian and Dalén Love (2025)
Genomic and morphological analysis reveals long-term mammoth hybridization in British Columbia, Canada Biol. Lett. 2120250305 http://doi.org/10.1098/rsbl.2025.0305
Copyright: © 2025 The authors.
Published by The Royal Society. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)
Creationists, on the other hand, are left clinging to a dogma that not only denies these mechanisms but insists that the entire process took place within a timescale that the evidence flatly contradicts. Their leaders will no doubt continue to misrepresent such research as a retreat from science, but the reality is precisely the opposite: it is science that explains the facts, while creationism can only ignore or distort them.
As with countless other discoveries, this research underlines the resilience and adaptability of evolutionary theory. It remains the only framework capable of making sense of the natural world — from the deep past of the mammoths to the living diversity we see today.
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