More than 40,000 years ago, the vast plains of North America were home to creatures that today seem almost mythical: mammoths. These enormous, shaggy relatives of modern elephants roamed the continent in herds, their curved tusks sweeping the air as they trudged across icy landscapes. For generations, scientists believed that two distinct species divided this frozen world. The woolly mammoth, with its thick fur and compact build, thrived in the cold northern regions of Canada and the northern United States. The Columbian mammoth, taller and less hairy, roamed further south where climates were milder and vegetation more varied.
It seemed like a neat picture: two species, adapted to different environments, living largely separate lives. But new research has upended that tidy division. Fossil teeth unearthed in Canada, when subjected to genetic analysis, revealed a surprising truth: these mammoths were hybrids. Columbian and woolly mammoths were not simply neighbors—they were partners, breeding together repeatedly over thousands of years.
This revelation paints a far more interconnected and dynamic story of North America’s Ice Age giants than scientists once imagined.
Discovering the Hybrid Mammoths
The key evidence comes from two fossilized molars found in western Canada. At first glance, they looked like the teeth of woolly mammoths. Yet when researchers extracted and sequenced their DNA, a different story emerged. Both belonged to hybrid animals—offspring of Columbian and woolly mammoths.
The older tooth, dating back around 36,000 years, contained roughly 21 percent Columbian mammoth DNA. The younger tooth, from about 25,000 years ago, showed an even stronger Columbian contribution: nearly 35 percent. The jump suggests that hybridization was not a rare accident but a repeated event, weaving together the genetic threads of both species over millennia.
Sex chromosome analysis offered another intriguing clue. The hybrids were most often the result of male Columbian mammoths mating with female woolly mammoths. This repeated mixing meant that woolly mammoths in North America were among the most genetically diverse populations of their kind, a fact that may have helped them adapt to shifting Ice Age climates.
A Long History of Interbreeding
The idea of mammoth hybridization is not entirely new. In 2021, scientists studying a 1.2-million-year-old mammoth tooth from Krestovka, Siberia, discovered that Columbian mammoths themselves were likely born from interbreeding. The evidence suggested that a population of steppe mammoths, an earlier ancestor, mated with woolly mammoths after crossing from Eurasia into North America.
That union appears to have given rise to the Columbian mammoth, a hybrid lineage from the very beginning. Up to half of the Columbian mammoth genome can be traced back to woolly mammoths. Now, with evidence that Columbians and woollies continued to mate long after their divergence, it seems hybridization was not a side note in their story—it was central to it.
This challenges long-held assumptions about evolution. For centuries, biology textbooks taught that species were distinct entities, unable to interbreed successfully. Yet advances in genetics are rewriting that view, showing that hybridization has shaped the history of many animals, humans included. Just as modern humans carry DNA inherited from Neanderthals and Denisovans, mammoths, too, were products of genetic exchange.
The Hidden Role of Natural Selection
One of the most fascinating findings from the new study is how hybrid mammoths looked. Despite carrying significant Columbian ancestry, their teeth closely resembled those of pure woolly mammoths. That similarity is not coincidence—it is natural selection at work.
In the cold, open plains of northern North America, woolly mammoth teeth—broad and ridged, perfect for grinding tough grasses—were the best tool for survival. Hybrids with different dental features would have struggled, so selection favored woolly-like teeth even in animals with mixed ancestry. The same principle would have applied further south, where Columbian mammoths lived. There, hybrids would retain teeth suited for a more generalist diet, because the environment demanded it.
This convergence shows how hybridization and natural selection can interact. Genes may mix, but survival pressures ultimately shape which traits persist.
Lessons from Extinction
Though hybrids may have boosted genetic diversity, even that could not save mammoths from extinction. As the Ice Age ended and climates warmed, grasslands gave way to forests. Humans also expanded across the continent, hunting mammoths and altering their habitats. By about 10,000 years ago, both woolly and Columbian mammoths had disappeared from mainland North America, their long legacy surviving only in fossils, myths, and scientific inquiry.
Yet studying their genetic history offers vital lessons for the present. Many living species today, from wolves to wildcats, face similar pressures as their ranges overlap with related animals. In some cases, hybridization may help them survive by increasing genetic diversity. In others, it could threaten unique lineages with extinction through genetic swamping. Understanding how mammoths navigated hybridization helps conservationists predict and manage these outcomes in modern ecosystems.
Hybrids and the Bigger Picture of Evolution
The story of hybrid mammoths reminds us that evolution is not a simple ladder but a tangled web. Species diverge, reconnect, and exchange genes in ways that blur boundaries. What might appear as a clean split on a family tree is, in reality, a complex network of relationships stretching across space and time.
Professor Adrian Lister, a co-author of the new study, emphasizes that the approach used to investigate mammoths could be applied to other extinct animals as well. By reconstructing the genetic histories of long-vanished creatures, scientists can uncover how hybridization shaped the diversity of life we see today.
The mammoths’ story also carries a deeper resonance. It reminds us that survival has always depended on flexibility, connection, and adaptation. In a time when Earth’s climate is changing rapidly once again, these lessons are more relevant than ever.
A Legacy Written in DNA
When we picture mammoths, we often imagine them as isolated giants: the woolly mammoth trudging through icy tundra, the Columbian mammoth wandering sunlit grasslands to the south. But the truth, written in their DNA, is that these species were far more interconnected than we imagined. They met, mingled, and raised calves together, reshaping one another in ways still visible tens of thousands of years later.
The discovery of hybrid mammoths is more than a detail of paleontology—it is a reminder that life is never static. Boundaries blur, species mix, and evolution writes its story not in straight lines, but in intertwined paths. In the frozen silence of their teeth, mammoths whisper to us across millennia: that survival is about connection, that diversity is strength, and that even in extinction, their story continues to guide our understanding of life on Earth.
More information: Genomic and morphological analysis reveals long-term mammoth hybridization in British Columbia, Canada, Biology Letters (2025). DOI: 10.1098/rsbl.2025.0305. royalsocietypublishing.org/doi … .1098/rsbl.2025.0305
