The fossil record, DNA and developmental biology all suggest that aquatic whales descended from ancestors that walked on land. The geographical distribution of some putative proto-whale fossils also seems to hint at this significant transition.
The proto-whale fossils that were almost completely land-dwelling, but likely spent at least some time in the water, include Indohyus and Pakicetus. When these animals first appear in the fossil record about 56–47.8 million years ago, they are found exclusively near the border of India and Pakistan .
In the next geological sequence, rocks dating to 47.8–40.3 million years ago, the proto-whale fossils show evidence of a stronger commitment to an aquatic lifestyle. For example, Ambulocetus and Remingtonocetus have anatomy that suggests they were similar to seals and sea lions, coming onto land occasionally but being particularly well-suited to life in the water. Rodhocetus, Artiocetus, and Protocetus take the aquatic commitment further with the presence of incipient blowholes and tail flukes. Georgiacetus was probably the closest to modern whales, having hindlimbs that were completely detached from the spine and therefore highly unlikely to support walking on land.
Some of these proto-whales and other are still found in the Indo-Pakistani region, much as you might expect if their ancestors arose from there.
However, given their further commitment to an aquatic lifestyle, they had the capacity to disperse to new parts of the world. Whereas Indohyus and Pakicetus likely would have had an extremely difficult time trying to cross the Atlantic and Southern Oceans, these animals almost certainly could have swam across, even if at the more narrow points. Indeed, the next generation of proto-whales include fossils found in Africa, Europe, Asia and even Antarctica.
Although the fine details are difficult to parse out given the relative coarseness of the geological record, the global distribution of proto-whale fossils seems to suggest that these animals originated in India and Pakistan, and, once they committed to the water they then spread across the globe.
Questions for Creationists
Why do we see this geographical pattern in putative proto-whale fossils? Why don’t we find the land-dwelling Indohyus and Pakicetus in places all around the world like we do for the aquatic photo-whales? Why would Indohyus, Pakicetus and some of the more aquatic proto-whales all migrate together to India and Pakistan after Noah’s Flood?
1. Fossil distributions from the Paleobiology database