In Defence of Earwax

For something that is located so close to our brains, we spend surprisingly little time thinking about our earwax. That is likely because earwax doesn’t appear to do a great deal for us. Mostly, it is just a nuisance that we have to clean out every once in a while.

That may be the common perception, but earwax is far more useful and interesting than we think. For starters, the type of earwax you produce is directly linked to your genetic ancestry and has implications for your personal hygiene. Yes, as it turns out, there are actually two distinct types of earwax. If your ancestors hail from Africa or Europe and you stick a Q-tip in your ear (something that is never actually advisable as you’re more likely to pierce an eardrum than to get anything clean) you are likely to pull out something yellow and wet. Undertake the same ill-advised ear regimen if you happen to come from a family with links to Northern Asia and your earwax is far more likely to be white, dry, and flakey.

It may seem like a trivial biological quirk, but evolution is a picky business and triviality is rarely tolerated. If it served no functional difference, we would expect the proportions of people with each type of wax to be basically random, but they’re not. Among Europeans and Africans, 97 to 100% have wet earwax and 80 to 95% of North Asians have dry earwax. The numbers are a little more mixed for South Asian, Native American, and Pacific Island Demographics (30 to 50%), but there is definitely some selection going on.

So what is the functional difference? Well, as unpleasant as it may be to hear, wet earwax is sticky and it stinks. The stickiness is thought to help keep insects from crawling into your ear canal if you are unfortunate enough to live somewhere where that is likely. As for the stink, we’re not sure, but it may have something to do with pheromones. Wet, smelly earwax is caused by the same genetic mutation that produces the chemical in sweat that bacteria feed uponto produce body odour, so those of us who are now self-conscious about the smell of our ears might need to stock up on deodorant as well.

Earwax isn’t only interesting because of the stench implications, however. It can also be used as a marker of physical health. Scientists can take a sample of your earwax and determine whether or not you are suffering from certain diseases, long before they could discern the same thing from your blood or urine. Ironically enough, the two diseases earwax is best equipped to diagnose in their early stages are ones named for their eventual effects on urine: Maple Syrup Urine Disease and Alkoptunuria (black urine disease). The former may sound hilarious, and is in fact named for the sweet smell it gives to urine, but that smell comes from enzymes a person’s body would normally use to provide nourishment. Peeing out things you need to live is generally bad news and Maple Syrup Urine Disease can be fatal.

Finally, earwax can be useful in determining details about personal life history. This isn’t something we use it for in humans just yet, but in 2007, when a blue whale died in a collision with a ship near Santa Barbara, California, marine biologists were able to use a plug of its earwax (which happened to be over 25 centimeters – or nearly 10 inches long) to determine the levels of stress hormones in its body and the contaminants in the water it swam through at various points in its life. Whale earwax is laid down in alternating light and dark layers, each representing about six months of time. Human earwax generally doesn’t get to this point, but it may still be useful in determining exposure to toxic chemicals and other harmful agents in forensics.

Try to keep all this in mind next time you carelessly stick a finger in your ear to scoop out some wax. The gunk on your finger holds secrets about your family, medical, and personal history. So, in a very real sense, you are what you pull out of your ears.

Whale Fall – More than just a hilarious existential crisis

Whale fall. It may sound like the rejected title of a James Bond movie or a Douglas Adams reference, but it is actually a surprisingly important and relatively little known concept in the study of the world’s oceans. It all begins with one of the saddest moments in the story of any whale family. Grandpa whale, let’s call him Moby, after a long a fulfilling life of eating ship captains’ legs, dies. 

As sad as this is for the rest of the whale family, odds are that if Old Moby died from natural causes he lived a pretty long life. Research beginning in the 1990’s revealed that a significant portion of the population of many whale species is over 100 years old. Questions started being asked when whale carcasses were pulled from the ocean containing stone harpoon heads, which fell out of fashion around 1860. Tissue samples from a group of Bowhead whales subsequently revealed that several were in their mid-100’s and one male was pushing 200. The point is whales can live a long time.

When a whale dies without human intervention its body either washes up on shore, occasionally with hilarious consequences, or it sinks to the bottom of the ocean. The latter is much more common and the result is something pretty remarkable.

When a whale fall, as these things are known, touches down the animals that live on the sea floor throw a party. The deep ocean is a surprisingly poor environment in terms of available food and energy with animals living mostly on small particles of so-called “marine snow” that drift down from above or by eating each other. A whale carcass, as you can imagine, is a welcome break from this kind of life.

The first phase of a whale fall food chain involves getting all that delicious, rancid flesh off the bones. That job is taken care of by animals like ratfish, sharks, crabs, and hagfish. The work goes surprisingly quickly. These scavengers can liberate up to 60 kg (132 lbs) of meat in a day. After a few short months (whales are big animals) only a skeleton remains. At first glance it would seem like the show is over, but in reality things are just heating up.

As the crabs and sharks pack up and move on to greener pastures, worms move in. Lots of worms. Polychaete worms, to be precise. Up to 45,000 worms per square meter blanket the sea floor about one year after the whale buffet opens its doors. They, along with a few other species of invertebrates, feast on the organic material in the whale bones. Although this stage of whale decay brings huge numbers of animals, they represent only a few species. The real fun begins when the microbes arrive on the scene.

Somewhere between one and two years into the show, most of the low hanging fruit (to use a more pleasant sounding metaphor) has been harvested. At this point sulphur-reducing bacteria arrive to feed on the fats and oils left in the skeleton. As they do this they release sulphur into the surrounding water, which attracts sulphophilic (sulphur-loving) bacteria. These bacteria, remarkable, form the basis for a very unique food web.

Most food webs on Earth begin with photosynthesis as plants turn sunlight into food. The web around this stage of a whale fall by comparison is chemosynthetic, meaning that it’s basis is chemical reactions by bacteria. Larger and larger animals feed on the bacteria and on the creatures that feed on the bacteria until eventually you have a booming community that includes up to 190 different species of visible animals. The only other place where this type of system exists is around deep sea vents where the energy comes from within the Earth itself.

These Stage Three whale fall communities can last a surprisingly long time. We're talking decades. Research has shown that some whale falls can sustain an ecosystem for over 50 years! And these are not rare systems. Given the number of whales alive today and the length of time that these communities last, scientists estimate that there may be a whale fall every 5 to 16 km (3 to 10 miles) along the sea floor, meaning that when the nutrients finally do run dry, the creatures that depended on them don’t have far to travel until they find their next home.

Whale falls are islands of biodiversity in one of Earth’s least bountiful places. Yet another reason why humans should do our part not only to protect whales, but to protect the fish and oceans that they depend on. 

Indecisive Evolution: Where did whales come from?

It is tempting to think of evolution as a linear process. You start with some primitive creature like an amoeba or a slug and over time you get rid of the slime, add some legs, maybe a bit of fur and you’re on your way to something more advanced. Unfortunately this is utterly and completely false. Natural history is full of examples of animals that just don’t change no matter how much time you give them. Crocodiles and sharks are two well-known examples but the clad of stubborn animals also includes horseshoe crabs, dragonflies, coelacanths and nautiluses just to name a few. Other animals oppose the idea of straight-line evolution in an entirely different way: they change, and then change their minds about changing.

It is strange to think that over millions of years a line of animals can commit to a new way of life, slowly accumulate the necessary genetic changes to become better and better at it, and then totally cut their losses and try to go back to what they used to be, but it happens all the time. The best example of the evolutionary yo-yo effect comes from everyone’s favourite paradoxes of the natural world, marine mammals.

The story of how we got whales, dolphins, seals and the like is a supremely interesting one that spans the entire history of life on earth. Actually, “interesting” is sort of in the eye of the beholder on this one because things kick off with the evolution of single-celled life around 3.6 billion years ago and then not much happens for about 3 billion years. After that, things got downright exciting, though. Multicellular marine life came onto the scene around 555 million years ago; the ancestors of scorpions, spiders; and millipedes took to the land 100 million years after that; land plants soon followed around 420 million years ago; and then, fashionably late to the land-dwelling party, four-limbed vertebrates crawled out of the ocean around 360 million years ago.

This last group is the one we are interested in. The animals that evolved from these air-breathing pseudo-fish became reptiles, dinosaurs, and all the mammals that have ever lived, including us (humans) and – perplexingly – marine mammals. Mammals as a group really came into our own in the dust of a global catastrophe around 65 million years ago. A massive object from space had just paid an unwelcome visit to Earth and wiped out the dominant creatures of the time, who we now know as dinosaurs. From the rubble of that world crawled a small, shrew-like animal that is the last common relative of everything from bats, to humans, to whales.

Lineages diverged and new species evolved for around 15 million years until around 50 million years ago a rebellious creature known to scientists by the name of Pakicetus decided it wanted to change things up. Pakicetus was an interesting animal. Imagine a wolf with an elongated head and hooves and you aren’t far off. We believe that they hunted animals both in an out of the water on the edges of oceans, because over time Pakicetus gave rise to other species that were more well-equipped for life in the water. Gradually the offspring of Pakicetus developed a longer tail and more hydrodynamic shape along with limbs better able to propel it through the water.

Over many generations these slight changes became more and more dramatic. The nasal passages moved up to the top of the head to allow for easier breathing at the surface, the tail became the primary means of propulsion to the extent that hind legs were only in the way and eventually shrunk down to basically nothing. These adaptations were incredibly successful and allowed this line of animals to grow into the largest animals that have ever lived on this planet: modern whales – as well as their smaller cousins, dolphins and porpoises.

Surprisingly, it only took about 10 million years to turn Pakicetus into the first recognizable whale (Dorudon), demonstrating that abandoning one way of life for another isn’t all that challenging for natural selection. If you want a snapshot of the midway point along this evolutionary line, take a look at seals, sea lions and otters.

Obviously, evolution’s work is never done. In spite of how well adapted these animals now are for life in the ocean, they still need to come to the surface to breath. Over time (a lot of time) that might change, or maybe they will transition back onto land as turtles and tortoises have done a number of times over the past many millions of years. All we know for sure, is that evolution plays by it’s own rules.

Sketchy Fact #38: Emotional Orcas

Scientists believe that Orcas (Killer Whales) are the second most cultural animals on Earth after humans. Scans of their brains show huge areas devoted to emotion and analytical skills. Separate groups have completely different hunting techniques and are even thought to have their own languages.