Whales have been falling on the same patch of seafloor for five million years

Start with what the deep sea normally eats. Down past four kilometres there is no light and no plants, so almost everything alive is waiting on scraps from far above: a slow, thin drizzle of dead plankton and shed skin and faeces, sinking for weeks. That drizzle is the entire economy. It is the reason the abyss is a place of small, patient, slow animals.

Then a whale dies, and forty tonnes of meat and oil-soaked bone hits the bottom at once. For the patch of seabed underneath, a single carcass delivers what the ordinary drizzle would take somewhere between one hundred and two thousand years to supply. Whole communities assemble on it and work through it in stages that can run for decades: scavengers first, then bone-eating worms, then bacteria living off the sulphides seeping out of the skeleton. More than four hundred species are known to use these places, and over a hundred and twenty species were first described from one.

Here is what makes it strange that we know any of this. Nobody had ever seen a whale fall until 1987, when Craig Smith found one by accident off southern California, a kilometre or so down. Since then the total found has stayed under fifty. Each one was treated as a piece of luck.

In February 2023 a Chinese crewed submersible, Fendouzhe, began diving on a place in the southeastern Indian Ocean called the Diamantina Zone. Over 32 dives the team mapped a corridor 1,200 kilometres long, at depths from 4,616 to 7,001 metres, and counted 476 fossil whale sites plus five active whale falls, one of them 6,789 metres down, the deepest ever seen. In places the bones lie at 759 individuals per square kilometre. Extrapolating that density across the whole zone gives more than ten million carcasses, and I want to be clear that this number is a projection, not a count.

The measured part is the part that undid me. Strontium in the oldest bones dates them to at least 5.3 million years. Whales have been coming down on this same stretch of seafloor since the early Pliocene, before anything in our genus was walking. The team thinks the zone’s V-shaped trenches funnel drifting bodies to the floor, that beaked whales hunt overhead, and that little sediment falls there, so the bones stay legible instead of being buried.

Here is the part I keep turning over. The rarest, richest event in the deep sea turns out to have an address, and it has been receiving deliveries for five million years without interruption. We have been aware of the whole phenomenon for thirty-nine of them.