November 27, 2020

I, Science

The science magazine of Imperial College

Starving and deranged, Jose Salvador Alvarenga survived thirteen months at sea ...

castaway-cravings-pic

In February 2014, Mexican castaway Jose Salvador Alvarenga washed up on the remote island of Ebon Atoll, just off the Marshall Islands, following thirteen months adrift in the Pacific in a small fishing boat. Alvarenga had set off on a fishing trip from Mexico in December 2012 with a young companion, who died at sea four months into their voyage.

When Alvarenga finally reached shore 8,000 kilometres later, he was in bad shape: emaciated, unable to walk and severely disorientated, he was wearing only ragged underpants and sporting a thick, tangled beard. But he was alive. For thirteen months he had survived on rainwater, turtle blood, seabirds, and fish caught with his bare hands.

But with food so scarce that his companion starved to death, how did Alvarenga’s body fight to keep him alive? And at what expense?

The human body can only go without water for three to eight days, but can survive for more than 70 days without food. During the lengthy process of starvation, the body re-distributes its resources, prioritising the delivery of energy to the most crucial organs. This buys valuable time so that the victim can (hopefully) find something to eat.

Only a few hours into Alvarenga’s fateful fishing excursion, the contents of his digestive tract were exhausted. With no carbohydrates left to break down, his body switched to breaking down glycogen, a storage form of glucose that is stockpiled in the liver and muscles. But just 24 hours later, this energy supply was exhausted too.

Alvarenga’s body then turned to its main energy warehouse – fat. Burning fat produces almost as much energy as burning carbohydrates, but it’s not as clean: it also produces acetone, which is excreted in the urine and exhaled in breath – so starving people smell like nail polish remover! Over a period of about two weeks, during which no replacement fuel supplies arrived, Alvarenga’s body began to slow down. Non-essential processes were switched off: his reaction time slowed, and production of infection-fighting cells and ‘unimportant’ chemicals like sex hormones decreased. Reproduction, it seems, takes a back seat during starvation.

Finally, with its fat stores depleted, Alvarenga’s body turned to its last resort – the protein that formed the structural and functional basis of all his body’s systems. His wasted condition when he washed up in the Marshall islands was the result of his muscles being burned for fuel, in a process comparable to burning your house down to keep warm. But Alvarenga was spared the final stage of starvation. By catching and eating sea birds and fish, he supplied his body with just enough fuel to hold off the digestion of the essential proteins making up his heart, liver, kidneys and brain. Sadly the same can’t be said for his companion, who couldn’t stomach Alvarenga’s raw meat and fish diet.

Non-obese individuals tend to die when their body weight has dropped by about one half. Clearly, we’re fairly good at eating ourselves alive. Indeed, with our fatty muscles and all the essential vitamins stored in our organs, humans actually make for a pretty balanced meal – more so than fish or turtles anyway. Of course it’s a little easier to justify eating yourself in this way than eating your friend…

A tradition of mariners

Stories of old suggest that a tradition of cannibalism used to travel the high seas as a matter of course: all mariners knew that this could become an acceptable survival technique in the event of a shipwreck. First to be sacrificed was the dying sailor, who was regarded as a helpless case consuming precious supplies. Keeping him alive would merely dry him out more, ultimately making him chewier and less nutritious. Following this, any surviving sailor – regardless of rank – was fair game, providing the selection was done fairly. The first round of straw-drawing would determine the meal; the second, the butcher.

Today, of course, cannibalism is an extreme cultural taboo in most societies. Passengers on the Mary-Jeanne – an island-hopping ferry in the Seychelles, which drifted for 74 days after running out of fuel in sight of its destination – chose to throw their dead comrades overboard, where they were eaten by sharks, rather than use their body parts as fishing bait or food. Two of the ten on board were eventually rescued, but perhaps more would have survived had it not been for the mental barrier that prevented one human from eating another.

Stranded in the Andes

In other instances, extreme stress and hunger have led to the breaking of this taboo. In 1972 a plane carrying the Uruguayan rugby team crashed in the Andes. Stranded without food in the icy mountains, and surrounded by frozen corpses, a group of survivors turned in desperation to eating their former teammates. This act of self-preservation meant they were strong enough to venture to lower ground, where they were eventually discovered and rescued. Of course, whatever the outcome, breaking a taboo is dangerous. Individuals who do so may be tempted to ignore other cultural restraints and lower their ethical standards (morality and fairness, for example), as primal instincts take over.

So there you have it. Perhaps if Tom Hanks had been Castaway with more than just a football for company, he would never have made it back. The concept of a ‘lucky’ castaway is a strange one, but it certainly seems that our drifting Mexican voyager, Alvarenga, may fit that bill.

IMAGE: LA(Phot) Dave Sterratt, Flickr – Royal Navy Aircrew conducts Sea Survival drills, using a single man life raft as part of their Sea Survival training.