Whales first evolved in Kashmir: Report

Evidence to back this comes from fossils of even-toed ungulates 8212; artiodactyls that spread their weight on their third and fourth toes 8212; which date from before the emergence of the whales, and of whale fossils that date from the first 10 million years of whale evolution.

But until now, scientists have lacked the 8220;missing link8221; of a fossil, which shows an emphatically close relationship between artiodactyls and cetaceans.

A team led by Hans Thewissen, a professor of anatomy at the Northeastern Ohio Universities Colleges of Medicine and Pharmacy, believe they have now found the coveted evidence.

They believe the ancestor of cetaceans is Indohyus, a racoon-sized herbivorous mammal that looked rather like a miniature deer and lived in water around 48 million years ago.

Thewissen draws this conclusion after sifting through a 50-metre layer of mudstone with hundreds of fossilized Indohyus bones found at Sindkhatudi, in the Kalakot region, in Kashmir.

The biggest similarity between whales and Indohyus lies in bones of the skull and ear and premolars, he says.

In addition, Indohyus bones have a dense outside layer 8212; much thicker than other mammals of this size 8212; which is a signature of animals that, like the hippopotamus, are slow aquatic waders.

The chemical composition of Indohyus8217; teeth also reveal oxygen isotope ratios similar to those of aquatic animals, implying that the animal spent much of its time in water.

Until now, it was speculated that whales evolved from meat-eating artiodactyls that became aquatic in order to feed on ocean-dwelling fish.

8220;Clearly, this is not the case,8221; says Thewissen. 8220;Indohyus is a plant-eater and already is aquatic. Apparently, the dietary shift to hunting animals, as modern whales do, came later than the habitat shift to water.8221;

A skeletal reconstruction of Indohyus by Thewissen shows a small, stocky artiodactyl that suggests it was not terribly good at swimming.

Instead, the little mammal spent most of its time wading in shallow water, quite possible for protection for feeding, with its heavy bones providing ballast to keep its feet anchored.

The new theory is that cetaceans originated from Indohyus, or a mammal that is closely-related to it, which gradually switched from a herbivorous diet to aquatic prey and then moved to life in the water.

Over time, the early whales adding the buoyancy mechanism, sense organs and oral skeleton that made them different from their ancestors and unique among mammals.

Thewissen admitted that it may initially seem strange that a deer-like animal could be the forerunner of huge mammals such as whales.

But, he said, the modern African mousedeer Hyemoschus aquaticus, also called the chevrotain, which is not closely related to whales, gives an idea as to how this evolutionary change could have happened. The mousedeer lives near streams and feeds on land but jumps into the water when in danger and even moves around at the bottom.