Hippos turn out to have one of the longest family lineages in Africa, according to a new study that finds hippos were among the first large mammals to invade Africa 33–35 million years ago.
Hippos turn out to have one of the longest family lineages in Africa, according to a new study that finds hippos were among the first large mammals to invade Africa 33–35 million years ago. The study, published in the journal Nature Communications, also sheds light on the unexpected family tree of these hefty, large-toothed animals -- including their close lineage to whales. Hippos are part of an animal group known as bothriodontines. Bothriodines "first appeared in Southeast Asia 37 million years ago," lead author Fabrice Lihoreau of Montpellier II University's Institute of Evolutionary Sciences explained to Discovery News. Some of these animals later traveled from Asia to Africa, "probably thanks to their ability to swim," he added.Angry Hippo Pursues Boat Full of Tourists
For the study, Lihoreau and his team analyzed remains of a newly discovered hippo ancestor,
. It lived about 30 million years ago. "We can say that it was an herbivorous mammal weighing 155-220 pounds with a size close to that of a large sheep," Lihoreau said. "However, it was 20 times smaller than the living common hippopotamus. It must have looked like a small and slender hippo."Million-Year-Old Fossils Show Hippos Going for a Swim
Gabriel Barathieu, Wikimedia Commons
Other DNA studies found that hippos are closely related to whales, but that seemed hard to believe. They are not exactly twins. The teeth of
clinched the whale connection, and also allowed the researchers to reconstruct the family tree of hippos. As for how two such different animals -- whales and hippos -- could be so closely related, Lihoreau explained that their more direct ancestors evolved in different environments. The pre-whale group existed near a continental sea between India and Asia and ate either fish or meat. The pre-hippo group (anthracotheres) "were found in swamp deposits on the continent, and might have been restricted to fresh water and only feeding on plants," he said. "These ecological differences might explain two divergent evolutions."Humpback Whales Get IMAX Treatment: Photos
The "sister group" to hippos includes, not only whales, but also dolphins and porpoises. These marine mammals don't fare well out of water, but hippos spend time both in water and on land. "Hippos are nowadays the last representatives, with beavers and capybaras, of a semi-aquatic lifestyle," Lihoreau said. He added that this way of living "was frequent in the past." Over time, it seems that most other species evolved to become either land or water specialists.Dolphins Swam into Mediterranean 18,000 Years Ago
The sister group of hippos and cetaceans (whales, dolphins and porpoises) are ruminants. These are mammals that feast on plants, which they then ferment in their specialized stomach prior to digestion. Cows are in this group.Video: Cow Farts Blow Up A Barn!
Deer are ruminants too -- so they are also related to hippos.Most Amazing Animal Friendships: Photos
Luca Galuzzi- www.galuzzi.it, Wikimedia Commons
Yet another ruminant is the giraffe. Goats, sheep and antelopes are ruminants as well, putting them on the crowded extended hippo family tree.Giraffe Population Drops 40 Percent in 15 Years
Richard Bartz, Wikimedia Commons
The most divergent family in the bunch includes wild boars. These scrappy animals are distantly related to hippos. They are native to much of Europe, Asia, the Greater Sunda Islands and North Africa.
J. Patrick Fischer, Wikimedia Commons
Camels are distantly related to hippos too. They are one of the most surprising members of the extended hippo family tree. While camels have evolved to withstand desert habitats, semi-aquatic hippos would not last long under such conditions. In fact, the hippo's unique skin has to be kept wet for much of the day. Their bodies overall can also dehydrate without sufficient water.
Llamas also belong on the extended hippo family tree. They are considered to be the native South American version of the camel, but they do not live in desert environments. Llamas instead have evolved for a high altitude existence.
Emily Killian Molina, Wikimedia Commons
Way down on the extended hippo family tree are members of the genus Canis, which includes wolves, coyotes, jackals and the domestic dog. Experts continue to debate canine history, but that of hippos is becoming more clear, thanks to the new study and other research. A big mystery still surrounds the precise common ancestor of hippos and cetaceans. In order to help identify this animal, the researchers are hoping to study when marine mammals became water specialists. Pinpointing when this occurred, Lihoreau said, "could help us reconstruct" the still mysterious long-lost ancestor, which might then be added to the already crowded hippo family tree.Dogs Strut Their Stuff at Westminster 2015: Photos
An ancient relative of the hippopotamus likely swam from Asia to Africa some 35 million years ago, long before the arrival of the lion, rhino, zebra and giraffe, suggests a new study.
Analysis of the previously unknown, long-extinct animal also confirms that cetaceans -- the group to which whales, dolphins and porpoises belong -- are in fact the hippo's closest living cousins.
"The origins of the hippopotamus have been a mystery until now," says study co-author Fabrice Lihoreau, a palaeontologist at France's University of Montpellier.
"Now we can say that hippos came from anthracotheres" -- an extinct group of plant-eating, semi-aquatic mammals with even-toed hooves.
Until now, the oldest known fossil of a hippo ancestor dated from about 20 million years ago, while cetacean remains aged 53 million years have been found.
Scientists had long lumped hippos with the Suidae family of pigs based on palaeontological finds, but DNA later suggested they were the kin of whales instead.
Yet the huge age gap between hippos and cetaceans in the fossil record left experts stumped.
"It meant that either we have never found ancestors of hippos, or we didn't recognise them among the mammal fossils we already had," says Lihoreau.
Now the remains of a 28-million-year-old animal discovered in Kenya has provided an important piece of the puzzle, according to a study in the journal Nature Communications.
Named Epirigenys lokonensis ('epiri' means hippo in the Turkana language and Lokone after the discovery site), it was about the size of a sheep, weighing in at 100 kilograms, which is about a twentieth the size of today's 'common hippopotamus', a sub-Saharan giant.
It may have spent much of its time immersed in water.
E. lokonensis was not a direct forefather of today's hippo, belonging instead to a side branch. But it lived much closer in time to the ancestor from which they both branched off, thus allowing for inferences to be drawn about the ancient animal.
Dental analysis led the team to conclude that E. lokonensis and the hippo both came from an anthracothere forefather, which migrated from Asia to Africa about 35 million years ago.
As Africa was then an island surrounded by water, it likely swam there.
All this means the ancestors of hippos "were among the first large mammals to colonize the African continent, long before those of any of the large carnivores, giraffes or bovines," all of which arrived only about 18 million years ago, say the researchers.
They suggest the modern-day hippo evolved independently in Africa, and is a creature truly endemic to the continent.
"We filled a gap in the evolutionary history of the hippo, bringing us closer to the point of divergence from their modern-day sister group of cetaceans," and thus a more accurate reconstruction, says Lihoreau.