Whales descended from a miniature deer-like creature that walked on four legs almost 50 million years ago.
Hans Thewissen, professor at Northeast Ohio Medical University, found that creatures from dolphins to whales are descended from Indohyus, a small deer-like creature that lived-in modern-day India and Pakistan.
Thewissen studied whale evolution for years and in his book, The Walking Whales: From Land to Water in Eight Million Years, he talks about the first-person account of discoveries that revealed early fossil records of whales.
Indohyus looked like a tiny deer, a deer the size of a cat and belonged to the even-toed group of ungulates which include animals like giraffes, cetaceans, pigs and horses.
Some of the earliest fossils of the creature were discovered among rocks collected in Kalakot region of Jammu and Kashmir by Indian geologist A Ranga Rao.
Rao found some teeth and parts of a jawbone in the 1960s and 70s but when he passed away, his wife Dr. Friedlinde Obergfell gave the rocks to Thewissen to study.
A further study into it revealed the fossil to be that of a 47-million-year-old animal with body and tail. His research examines the stable isotopes in Indohyus fossils, discovering that they ate land plants and their dense bone structure found they spent a lot of time in water.
A hippopotamus is believed to be the closest living relative of whales that lives on land, its dense bone structure helps in walking along the bottom of lakes and rivers.
Since Darwin’s theory, it has been known whales descended from a land walking mammal but the exact name remained a mystery, which was solved by fossils discovered in India-Pakistan region.
The aquatic habits of Indohyus can be further studied by their teeth’s chemical composition, levels of carbon and oxygen isotopes differ in the tooth enamel of land- dwelling animals and aquatic animals due to the different isotope compositions in the food and water they consume.
Earlier, it was believed that whales descended from carnivorous animals who shifted to an aquatic lifestyle to look for food in fish.
Thewissen describes the first ancestors of whales as similar to sea lions, which emerged 42 million to 48 million years ago, followed by Baleen, around 41 years ago, ancestors of humpbacks and blue whales. These were followed by toothed whales around seven million years later which can be seen swimming in the oceans today.