DNA Pinpoints Where Camel Breeding Began
Until now, no one had been able to determine where the distinctive, one-humped creatures were first domesticated.
The dromedary, or Arabian camel, has transported people and materials in the Middle East and North Africa for thousands of years. But, until now, no one had been able to determine where the distinctive, one-humped creatures were first domesticated.
In a new study, researchers from the University of Veterinary Medicine in Vienna say they have figured it out.
After comparing DNA of wild and early-domesticated dromedaries as much as 7,000 years old with the genetic samples of more than 1,000 modern dromedaries , the team determined that the Southeast Arabian Peninsula was the birthplace of dromedary domestication.
"Our results appear to confirm that the first domestication of wild dromedaries occurred on the southeast coast," said lead researcher Pamela Burger. "This was followed by repeated breeding of wild dromedaries with the early-domesticated populations."
Those wild ancestors of today's dromedaries, Burger noted, went extinct about 2,000 years ago.
While most animals that are domesticated end up with less genetic diversity, as breeders repeatedly focus on specific things, Burger and her colleagues found remarkable genetic diversity in dromedaries.
DNA analysis told them that this diversity came from the nature of the dromedary's lifestyle. Long-distance travels along ancient caravan trade routes put the animals in regular touch with other populations, leading to what the scientists called "regular gene flow," of a kind usually only seen in wild animals.
It was that diversity, the researchers said, that made it historically difficult to determine which region held the ancestor of domesticated Arabian camels.
Burger and her team's findings have been published in the journal Proceedings of the National Academy of Sciences.
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.
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."
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."
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.
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.
Deer are ruminants too -- so they are also related to hippos.
Yet another ruminant is the giraffe. Goats, sheep and antelopes are ruminants as well, putting them on the crowded extended hippo family tree.
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.
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.
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.