NOVA: "When Whales Could Walk" (WGBH, PBS, aired January 31, 2024)

by Mark Gabrish Conlan • Copyright © 2024 by Mark Gabrish Conlan • All rights reserved

Last night (Wednesday, January 31) at 9 I put on PBS for a couple of science shows, a 2024 episode of NOVA called “When Whales Could Walk” and a 2015 Secrets of the Dead show called “Jamestown’s Dark Winter.” “When Whales Could Walk” actually turned out to be the more interesting of the two – I’d expected it would be the other way around – and it began in a desert valley in Egypt where paleontologist Hesham Sallam from Mansour and American Universities in Cairo had unearthed a giant fossil containing a complete skeleton of a 60-foot-long animal called Basilosaurus. The name indicates a dinosaur, which was what the original discoverers of Basilosaurus thought it was, but eventually they realized it was a prehistoric forerunner of modern-day whales. One difference between Basilosaurus and modern whales is it had legs and feet so it could walk and hunt down prey on land as well as in the water. Modern whales have the remnants of their original legs which, much like the vestigial front limbs of Tyrannosaurus rex, are too small to support its weight if they had tried to walk on land, but they’re there and in at least some whale species they’ve evolved into flippers. Another researcher, Arnold Gingerich, had gone to Pakistan in search of prehistoric horses; he didn’t find any, but he found fossil remains of an animal now called Pakicetus that, though only one-third the size of Basilosaurus, not only could walk on land but hunted for prey there as well as in the water. Smithsonian Institution scientists Ellen Coombs and Mithriel MacKay got a rare chance to dissect a beached whale and discovered, among other things, that whales have nine stomachs – suggesting that, like cattle, their ancestors subsisted on grasses and other land-based plant life and needed the multiple stomachs to digest it.

One group of interviewees suggested that the closest living relatives to the prehistoric amphibian whales are hippopotami, who live along riverbeds and spend much of their lives in the water, even though they come up on land to eat and have sex. The reason whales eventually retreated to the ocean and became totally aquatic is explained by the global cooling that happened about 34 ½ million years ago, which caused the Mediterranean Sea to shrink from its prehistoric dimensions to its current ones. They figured this out mainly from the fossilized trees that started to appear in the Egyptian strata from that time, and they assumed that the way whales survived the disappearance of their habitats was to evolve into a totally water-based animal, though as a marine mammal they were still obliged to surface regularly to breathe air before returning to the ocean. The show also discussed the two separate types of whales, one group that retained the teeth they had as land animals and the other that rely on baleen, long fibers of keratin (the same material as in hair) that filter out edible food like fish and krill from great volumes of ocean water and use that as their nourishment. The whales that have teeth sometimes feed on the whales that don’t; there’s interesting footage here of a baleen-whale mother trying to protect her calf from the predatory teeth-bearing whales who are looking at her calf as a potential food source. It also suggested that the reason whales evolved into the largest animals in earth’s history is that they needed to be that big to be able to swallow enough ocean water and filter out the edible materials from it. This NOVA program was a quite fascinating one that told me things about whales and their ancestors I’d never heard of before, and that’s what a science show on TV should do.