Three times the mammals returned to the sea—
Three separate lineages, three independent
Experiments in aquatic sovereignty,
And each time the body's transcendent
Engineering rebuilt the land-walker
Into the swimmer, the diver, the ocean's lord.
The first and greatest was the whale—the stalker
Of the deep who began as a walking horde
Of small, dog-like creatures on the shore
Of the Tethys Sea in the Eocene's
Warm shallows—Pakicetos, no more
Than a wolf in size, whose genes
Would produce the largest animal
That has ever lived on earth.
From Pakicetos' shallow, analytical
And fish-hunting wading at the berth
Of the Tethys coast, the whale's transition
Proceeded step by step: Ambulocetos
Was the walking whale, the rendition
Of a crocodile-like swimmer whose veto
Of the land was not yet complete—
He walked and swam, an amphibious hunter
Whose hind legs still met the beat
Of the ground but whose front legs were the punter's
Paddles in the coastal water.
Then Rodhocetos—the hind legs shrinking,
The nostrils migrating, the slaughter
Of the land-body's architecture sinking
Toward the streamlined form—and Basilosauros,
The ancient whale, sixty feet of serpentine
And fully aquatic ocean's chorus,
Whose tiny vestigial hind-limbs' line
Was the last memory of the land
That the whale would ever carry—
By the late Eocene, the command
Of the ocean was the cetacean's missionary
Position: the whale was fully marine.
And then the great division: Odontocetos—
The toothed whales—invented the machine
Of echolocation, the subaqueous
Sonar of the dolphin and the sperm whale—
The melon in the forehead focusing
The click into a beam, the tale
Of the echo's return producing
A three-dimensional map of the dark
And murky ocean—the dolphin sees
With sound, and the sound paints the shark
And the fish and the squid in the deep-water frieze
Of the acoustic world.
And Mysticetos—
The baleen whales—grew the largest bodies
That life has ever made: the cetacean's
Grottos of the ribcage and the body's
Cathedral of the blue whale's hundred feet
And hundred and fifty tons—the largest
Animal in the history of the fleet
Of the living—fed not on the largest
Prey but on the smallest: the krill,
The tiny shrimp scooped in the baleen's
Comb of keratin, the fill
Of a thousand pounds of protein
Filtered from the ocean every day.
The whale sang—the humpback's song
Traveled hundreds of miles through the gray
And acoustic ocean, the long
And complex melody that the males
Composed and revised across the breeding season—
No two years the same, the whale's
Song evolving in real time, the reason
Unknown but the beauty undeniable:
The ocean filled with music
Made by the largest animals' reliable
And haunting and acoustic
Declaration: I am here, and I am vast,
And I am singing.
The second return to the sea
Was Pinnipedos'—the carnivore's forecast
Of the ocean's opportunity—already told
In the carnivorans' chapter,
The seal's transformation from the bold
Land-hunter to the chapter
Of the marine—the flippers, the blubber,
The deep-dive physiology
That collapses the lung like rubber
And stores the oxygen in the biology
Of the blood and muscle, not the air.
And the third return was Sirenios'—
Already told in Afrotheros' care,
The manatee's and dugong's areas
Of the seagrass meadow, the gentle grazer
Of the tropical coast.
Three times the mammal went to sea.
Three times the body was the eraser
Of its own terrestrial design,
And three times the ocean wrote a new
And streamlined body from the line
Of the walker's bones—and the blue
And singing and the deep and diving world
Of the marine mammal was the proof
That Mammos' banners, once unfurled
On land, could conquer the aloof
And ancient ocean too—the synapsid's return
To the water that the amniotic egg
Had left behind, the ancestral yearn
For the sea that every land-thing's leg
Still carries in the salt-blood of its veins.