Some Whales Are Born With Legs

The coast of southern Alaska grows glaciers and brooding rain forests.

Hot weather is rare, but since sunup the day had brought nothing else.

By afternoon everyone was sweltering.

The first person to do more than just talk about leaping off the boat into iceberg-chilled Frederick Sound performed a cannonball. Others jackknifed and belly flopped in.

This contest to raise the biggest splash was spirited but short. No sooner had the last person shivered back aboard than three humpback whales surfaced exactly where the jumpers had been landing.

The whales lingered a while, misting the crew with spray from their blowholes, then eased down out of sight.

 We were still exclaiming about the visit minutes later when the sea to starboard erupted. A 45-foot (14-meter) whale went skyborne up to its tail.

Then a pair leaped in near synchrony. Shwa-boom! Ker-bloosh! Others started to breach on all sides.

For the next half hour humpbacks were flying and crash landing, sending out minor tsunamis, floating head down to whap the water with their tail flukes, and lying on their sides to slap the surface with long pectoral fins.

 It would be the height of arrogance to think we inspired 40-ton (40,000-kilogram) organic submarines to compete with us.

But I saw what I saw. Whales have a way of making the incredible real; their very name has become a metaphor for something almost too big to get our minds around.

I wondered what the crews on whaling ships thought when they would occasionally haul aboard a fully grown adult with miniature legs sticking out from its flanks.

Whether they knew it or not, they were looking at testimony to the origin of these mysterious marine giants.

 More than 80 living species of mammals are classified as whales, or, as taxonomists say, cetaceans (from ketos, the Greek name for sea monster).

 They can be divided into two groups. Mysticetes, or baleen whales, use comb-like plates hanging from the roofs of their mouths to strain food from seawater.

Blue whales, fin whales, bowheads, and most of the other real titans belong to this division along with smaller types such as minke whales and pygmy right whales.

Odontocetes, or toothed whales, include belugas, narwhals, sperm whales, pilot whales, and beaked whales plus all the dolphins and porpoises. We call the largest dolphins killer whales.

 But what did the first whales look like? And what gave rise to them? For a long time scientists could only speculate, for the oldest fossils anyone knew of had already assumed the basic appearance of whales.

In the absence of intermediate forms, people proposed almost every type of mammal as ancestors.

 At last a series of fossil discoveries has unveiled whales’ distant past. Paleontologists can suddenly trace the most colossal animals ever to appear on Earth step-by-step back to their beginnings early in the Eocene epoch, often referred to as the dawn of the age of mammals, which lasted from about 55 million to 34 million years ago.

Source: National Geographic