Sunday, March 19, 2006

Time Machine: Journey One

During a visit to the National Museum of Natural History and Science (New York, NY) years ago, I was awestruck by the display of creatures that roamed this planet before we were ever a gleam in evolution’s eye. Always captivated by the giants who preceded us, I commented to my companion during that visit that if we had time travel I would be one of the first to volunteer to go back and be an ‘Observer’. When prodded what I would like to see or do if I had once chance to go back in time, I couldn’t respond (perhaps for the first time). Too many events flooded my mind.

During the three years ensuing that visit, I have pondered that question again and often: What would I do, where and when would I go, and what event in time do I want to see? This is a series of responses to that question. Sorry, Mark; life is not that simple to provide one answer.


Skunks

Spring is here in Texas; it is the time of flowing pheromones and nature’s drive to reproduce where ever it can. Two and four-footed creatures are on the move to seek a mate, or just mate. As I drive down country roads I see and smell that little black and white furry bugger that isn’t so cute: skunk. Occasionally I wake to the malodour of Pepe Le’ Pew, such as this morning. Having been a victim at close range many years ago, suffering a direct hit, I still have an associated cringe and and clenching of the stomach, along with an almost reflexive attempt to block the smell and taste of skunk perfume.

This morning I was awoken by a strong skunk presence, enough to incite me to jump out of bed and clang the bedroom windows shut. Glancing out one window, I saw my arch enemy returning my gaze below with what could be interpreted as a “Heheee…gotcha” expression.

During my drive to town with a slight scent of skunk lingering on my clothes, I contemplated going back in time to find the ancestor with the culprit scent gland before it mated with the scentless ancestor of our modern skunk and removing it from the evolutionary chain.

The skunk family Mephitidae (derived from Mephitis, Latin for "bad odor") comprises of 11 species in four genera. Nearly all carnivores have scent glands, but they are especially enlarged in skunks and relative families, with skunks taking that enlargement to an extreme. Rather than a duct like it’s close ‘cousins’, the skunk scent glands at the base of the tail has a nipple. The glands contain approximately 15 cc of a yellowish, oily liquid. With highly coordinated muscle control, the skunk can aim and direct the spray as far as 15 feet and spay up to six times in succession. The only relief is that it takes up to 10 days to replenish the supply of liquid after full discharge.

The odoriferous liquid contains various thiols (sulfur compounds) and thioacetates (salts of sulfur compounds). The principle compound in skunk musk is butyl mercaptan, similar to the popular laboratory compound mercaptoethanol used to cleaving disulfide bonds in organic solutions (to this day I cannot go into a lab without cringing at the smell of mercaptoethanol). Being sprayed in a direct hit can cause temporary blindness, nausea, convulsions, loss of consciousness and burns of the skin.

To neutralize skunk odor, the thiols have to be changed into compounds that have little or no odor. This can be done by oxidizing the thiols to sulfonic acids. Common oxidizing agents are hydrogen peroxide and baking soda (sodium bicarbonate) and are mild enough to be used on pets and yourself although it may change hair color. For clothes and inanimate objects sodium hypochlorite solutions (liquid laundry bleach) works well.

Skunk Evolution

Scent glands are ubiquitous throughout the class of mammals and serve as a form of olfactory communication. Distinctive and long-lasting smells are distributed in urine, sweat, or released by rubbing. These scents are deposited on the ground, on territorial boundaries, on offspring or mates, or their habitats. Yet the skunk has evolved to use their scent glands as a defensive weapon. Tail up, point, aim and shoot. Anyone taking a direct hit can attest to burning eyes, gagging, inability to breathe and rubbing any exposed skin to rid thyself of the noxious semi-viscous fluid and its aerosols.

What ancestor provided this adaptive trait? The oldest fossil identified as a skunk was discovered in Germany and dates to 11–12 million years ago. However, genetic data indicate the family originated about 30–40 million years ago. Research traces the evolution of the skunk from some of the earliest ancestors of modern carnivores and as members of the superfamily containing those of otters, badgers, and weasels, raccoons, and red panda. It is suggested that the origin of the skunk lineage occurred in the Oligocene approximately 40 million years ago (about 30 million years before the appearance of the first recognized fossil).

At some point in time, a weasely mammal sauntered up to a close relative and whispered in its ear “Hey baby, I have a secret weapon. Want to see it work?” Thus the lineage of the cute little furry buggers avoided becoming someone’s dinner. And they multiplied, with the semi-viscous stench dictating survival and adaptation.

I wonder if they had scent gland firing ranges for practice.

1 comment:

  1. Because I'm into self abuse I attended a creationist lecture running on about the absolute implausibility of evolution. The poster child they paraded out was the skunk. They said that science has no way of explaining how skunks evolved their pungent oder. Their answer to this dilemma was that only a designer could have inflicted such stench on humanity. Thank you for your insightful explanation of how skunks evolved scent as a defense.

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