Twist in the tail: whales wolf-sized ancestors once walked the land
Fossils bridge gap between land mammals and whales.
Fifty million years ago, two mammals roamed the desert landscapes of what is now Pakistan. They looked a bit like dogs. They were, in fact, land-living, four-legged whales.
Their new-found fossils join other famous missing links, such as the primitive bird Archaeopteryx, that show how one group of animals evolved into another. And they undermine the two prevailing theories about which land mammals are most closely related to cetaceans - whales, dolphins and porpoises1.
Toeing the line
Because cetaceans are so unlike any land mammal, with their legs as paddles and their nostrils atop their heads, it has been immensely difficult to place them in the evolutionary scheme of things.
Earlier fossil studies related them to the mesonychians, an extinct group of meat eaters. The new discoveries send this idea "out the window", says Thewissen.
Less likely to be abandoned on the strength of Thewissen’s evidence is an alternative hypothesis, based on DNA sequence analysis. This is the idea that cetaceans are more like hippopotamuses (another even-toed ungulate) than any other land mammal.
"Almost all the molecular data place cetaceans within the living even-toed ungulates, as a sister group to hippopotamuses," says evolutionary biologist Ulfur Arnason of the University of Lund in Sweden.
Rapid evolutionary change, be it molecular, ecological or anatomical, is extremely difficult to reconstruct, and the speed with which cetaceans took to the water may make their bones an unreliable guide to their ancestry, he says
Arnason believes the two camps will remain divided, at least for now. "There’s no point trying to reach some sort of consensus based on compromise. It has often been very difficult to reconcile morphological and molecular opinions," he says.
JOHN WHITFIELD | Nature News Service
Bacteria use their enemy -- phage -- for 'self-recognition'
23.04.2019 | Chinese Academy of Sciences Headquarters
Scientists propose new theory on Alzheimer's, amyloid connection
23.04.2019 | Florida Atlantic University
Researchers led by Francesca Ferlaino from the University of Innsbruck and the Austrian Academy of Sciences report in Physical Review X on the observation of supersolid behavior in dipolar quantum gases of erbium and dysprosium. In the dysprosium gas these properties are unprecedentedly long-lived. This sets the stage for future investigations into the nature of this exotic phase of matter.
Supersolidity is a paradoxical state where the matter is both crystallized and superfluid. Predicted 50 years ago, such a counter-intuitive phase, featuring...
A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter
A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.
Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...
The technology could revolutionize how information travels through data centers and artificial intelligence networks
Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...
Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.
Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...
17.04.2019 | Event News
15.04.2019 | Event News
09.04.2019 | Event News
23.04.2019 | Life Sciences
23.04.2019 | Physics and Astronomy
18.04.2019 | Life Sciences