Are Javelinas Related to Hippos? A Look at Their Lineage

Javelinas are not closely related to hippos. Despite a passing physical resemblance and an old taxonomic tradition that once lumped them loosely together, molecular and fossil evidence places these two animals on separate branches of the mammalian family tree that diverged tens of millions of years ago. Javelinas, properly called peccaries, belong to the pig side of the even-toed ungulate order, while hippos sit on a completely different branch whose closest living relatives are, surprisingly, whales. The confusion is understandable, but the science is clear.

Where Javelinas Sit on the Family Tree

Javelinas belong to the family Tayassuidae, the peccaries. There are three living species: the collared peccary (the animal most people in the American Southwest call a javelina), the white-lipped peccary of Central and South America, and the Chacoan peccary of the Gran Chaco region in South America. All three are grouped within the suborder Suina, which also contains the family Suidae, the Old World pigs. Genetic studies have confirmed that pigs and peccaries form their own exclusive group on the evolutionary tree, separate from hippos.

A landmark analysis of genetic markers across all major even-toed ungulate lineages found that pigs and peccaries form a monophyletic group to the exclusion of hippopotamuses.¹ In other words, peccaries share a more recent common ancestor with the domestic pig or the wild boar than they do with any hippo. Think of it this way: javelinas and pigs are siblings in evolutionary terms, while hippos are more like distant cousins several times removed.

Where Hippos Actually Belong

The biggest surprise in ungulate evolutionary biology over the past few decades has been the realization that hippos are more closely related to whales and dolphins than to any pig-like animal. Multiple independent lines of genetic evidence, from mitochondrial DNA to mobile genetic elements embedded in the genome, all point to the same conclusion: hippos and cetaceans share an exclusive common ancestor.

Analyses of mitochondrial genomes separated the hippopotamus from pigs entirely and identified hippos as the closest living relatives of cetaceans, making the old classification that grouped hippos with pigs and peccaries outdated.² This finding was reinforced by studies using a different technique, looking at distinctive chunks of DNA that insert themselves into specific chromosomal locations and serve as nearly irreversible evolutionary markers. Those analyses also confirmed the hippo-whale group as a natural unit, firmly separate from the pig-peccary group.¹

The story holds up from the fossil side too. Research into hippopotamid origins has pointed to an extinct family of large, semi-aquatic herbivores called anthracotheres as the likely ancestors of modern hippos. Fossil studies and molecular comparisons converge on the anthracotheres as the stem group that eventually gave rise to the hippo lineage, which then branched off from the line that became whales far earlier.³ So when you look at a hippo, you are looking at an animal that is genealogically closer to a bottlenose dolphin than to the javelina rooting through your yard in Tucson.

Why the Confusion Exists

The idea that javelinas and hippos might be related comes from a combination of looks and old taxonomy. Peccaries have a barrel-shaped body, a large head, short legs, and a generally pig-like silhouette. Hippos are much larger but share that same stocky, round-bodied profile. Both have tough, relatively sparse hair rather than fur, and both are herbivores with powerful jaws and prominent tusks or tusk-like canines. To a naturalist working before the era of DNA analysis, it was reasonable to group them together in a broad category of pig-shaped, non-ruminant herbivores.

For much of the 19th and 20th centuries, taxonomists placed hippos within a group called the Suiformes, which also contained pigs and peccaries. The grouping felt intuitive. These were all heavy, barrel-bodied, non-cud-chewing animals with simple stomachs (or so it was thought at the time). But molecular evidence dismantled that arrangement in the late 1990s and early 2000s, pulling hippos out of the pig-peccary group and placing them next to the cetaceans. The old “Suiformes” grouping turned out to be an artifact of convergent body shapes rather than shared ancestry.

What Convergent Traits Actually Look Alike

If javelinas and hippos are not close relatives, why do they share certain features? The answer is that similar ecological pressures can push unrelated animals toward similar body plans. Thick skin, a compact build, and strong jaws are useful adaptations for a ground-dwelling herbivore that needs to process tough plant material and defend itself against predators. These traits evolved independently in peccaries and hippos, driven by similar environmental demands rather than inherited from a recent common ancestor.

One trait that illustrates the false sense of kinship is foregut fermentation. Both peccaries and hippos have complex, multi-chambered stomachs that ferment plant material before it reaches the intestine, a feature more commonly associated with ruminants like cattle and deer. A study measuring methane production from digestion compared the collared peccary and the pygmy hippopotamus, noting that both are non-ruminant foregut-fermenting herbivores.⁴ That shared digestive strategy sounds like evidence of close kinship, but it is not. Complex stomachs have evolved multiple times across mammalian lineages. Peccaries and hippos each arrived at their digestive setup independently, which is why the genetic evidence so clearly separates them despite the anatomical parallel.

Old World pigs, by contrast, have a simpler stomach. So peccaries do not even share this particular digestive trait with their closer relatives in the Suidae. This is a case where convergent evolution produced a similarity between two distantly related animals while the closer relatives diverged in a different direction.

The Deep History of Peccaries

Peccaries have a long and distinct evolutionary history in the Americas. Their family, Tayassuidae, originated in North America and was once far more diverse than it is today. From the Miocene epoch through the Pleistocene, now-extinct peccary species inhabited the entire continent. One of the best-known extinct species is the flat-headed peccary, Platygonus compressus, which was one of the most commonly found subfossil mammals in North America before it disappeared at the end of the last Ice Age.

Ancient DNA analysis placed the flat-headed peccary as a sister group to all living peccary species, meaning it branched off before the three modern species diverged from one another.⁵ The dating estimates from that same analysis suggest that the ancestor of today’s peccaries dispersed from North America to South America well before the Isthmus of Panama fully formed, which has complicated longstanding assumptions about when and how animals moved between the two continents.⁵ The collared peccary, the javelina you encounter in the southwestern United States and Mexico, eventually recolonized parts of North America from that South American diversification.

This history underscores how separate the peccary lineage is from the hippo lineage. While peccaries were radiating across the Americas, hippos were evolving in Africa from their anthracothere ancestors, eventually giving rise to just two surviving species: the common hippo and the pygmy hippo. The two families were never on the same continent at the same time in any meaningful evolutionary sense.

The Deep History of Hippos

Hippos trace their ancestry to the anthracotheres, a diverse and now completely extinct family of large, often semi-aquatic herbivores that lived across Africa, Europe, and Asia. The anthracotheres thrived for tens of millions of years before most lineages died out, leaving only the hippo branch behind. Fossil evidence from early Miocene deposits in Africa has helped researchers reconstruct the sequence of dental and skeletal changes that link advanced anthracotheres to the first recognizable hippos.⁶

The anthracothere-to-hippo transition is also significant because it confirms where hippos sit relative to whales. The anthracothere family itself is nested within the broader group that includes cetaceans, meaning hippos did not evolve from something pig-like and then converge toward whale-relatives by coincidence. Instead, hippos evolved from a lineage that was already on the whale side of the even-toed ungulate tree.³ Researchers reviewing the morphological evidence found that while some features shared by hippos and anthracotheres evolved in parallel, the anthracotheres remain the best candidate for the hippo stem group based on the available character evidence.⁷

How the Whole Order Fits Together

To understand where javelinas and hippos sit relative to each other, it helps to see the big picture of their shared order, Cetartiodactyla. This is the superorder that contains all even-toed ungulates and all cetaceans (whales and dolphins), because genetic evidence made it impossible to keep them separate. Within this large group, the evolutionary history was punctuated by several bursts of rapid diversification during the Cenozoic era, including the early split that produced three main lineages: the ruminant-whale group (called Cetruminantia), the pig-peccary group (Suina), and the camel group (Tylopoda).⁸

Camels branched off first. Then the pig-peccary group split away. That left the ruminant-whale group, within which hippos are tucked alongside cetaceans. This branching order means that javelinas are about as distantly related to hippos as they are to deer or giraffes. The split between Suina and the ancestors of hippos happened deep in the Cenozoic, roughly in the range of 60 million years ago. By the time the pig lineage and the hippo lineage could be recognized as distinct, they had been on separate evolutionary trajectories for a very long time.

A comprehensive study sequencing 128 new complete mitochondrial genomes across all cetartiodactyl families confirmed these branching patterns and identified several phases of rapid radiation, including diversification events at the Oligocene-Miocene boundary and in the middle Miocene that shaped the modern diversity of both cetaceans and ruminants.⁸ Peccaries are not part of those later radiations. They had already been on their own path for millions of years by then.

Javelinas Versus Pigs

If javelinas are not related to hippos, are they at least the same thing as pigs? Not quite. Peccaries and pigs share a common ancestor and are grouped together in Suina, but they split from each other a long time ago and have accumulated many differences. Peccaries are exclusively a New World family, while true pigs are Old World animals (the feral hogs roaming parts of the Americas are descendants of domestic pigs brought by European colonists, not native species). Peccaries are generally smaller, with a maximum weight around 40 kg for the largest species, while wild boars can exceed 200 kg.

There are also structural differences. Peccaries have a scent gland on their back near the rump, which is absent in pigs. Their canine teeth point downward rather than curving outward like a boar’s tusks. They have fewer toes on their hind feet (three instead of four), and as discussed, their stomachs are more complex. So while calling a javelina a “pig” is closer to the truth than calling it a “small hippo,” it is still technically wrong. Peccaries are their own family with their own evolutionary history.

Living with Peccaries in the Modern Southwest

The collared peccary has been expanding its range northward in recent decades. Animals that were once confined to southern Texas and southern Arizona are now showing up in areas where they were rarely or never seen before. Part of this is climate-related, as milder winters allow peccaries to survive farther north, and part of it is habitat connectivity. Javelinas are adaptable feeders, eating prickly pear cactus, mesquite beans, roots, insects, and occasionally small animals. In suburban areas, they quickly learn to exploit landscaping plants, pet food, and garbage.

Their social behavior is more complex than most people realize. Collared peccaries live in herds of around 6 to 12 individuals and maintain strong social bonds reinforced by mutual scent-marking using the dorsal gland. They are not aggressive by nature, but a herd that feels cornered, especially one with young, can charge and inflict real bites with those sharp, downward-pointing canines. Dogs off-leash are the most common trigger for confrontations, because peccaries perceive them as predators.

None of this behavior has anything in common with hippo behavior. Hippos are semi-aquatic, spend most of their day submerged in water, are fiercely territorial in rivers and lakes, and are among the most dangerous large animals in Africa. The ecological niche, social structure, and daily habits of peccaries and hippos could hardly be more different, which reflects just how long ago their lineages parted ways. A javelina rooting through a Scottsdale backyard at dusk is doing something no hippo has ever done, and its ancestors have been on a separate evolutionary path for longer than the Rocky Mountains have existed in their current form.