The Essentials: The X-Flies

A friend of mine told me that he was comped two drinks a while back.  The first was because there were fruit flies in the glass and the second for the same reason.  He speculated that the establishment neglected to cover their bottles over night and the flies enjoyed their own free drinks.  The story immediately reminded me of a study that showed how an attraction to alcohol was advantageous to the flies.

Fruit flies could have just as easily been named bar flies because their habits lead them to imbibe in alcohol on a regular basis.  Fruit flies dine on over ripe, and therefore fermenting, fruit.  The fermentation process converts the fruit sugars into alcohol and in that way alcohol becomes part of the fly’s daily diet.  The study showed that alcohol consumption increased the flies fitness because it helped them ward off attacks from a would be predator.

The foiled predator is of the most insidious and sneaky kind.  This predator attacks undetected (possibly) and from within. This predator is a parasite: specifically a parasitic wasp. The strategy of the wasp is to get its eggs into the fly, then once the eggs hatch, the newborns feast on the fly from the inside out.  As a result the wasp has a buffet of fresh fly guts to feast on and the fly dies from the inside out.

The fly has no real defense against the parasitic attack.  There are no fly surgeons to extract the unwanted wasps and left untreated the prognosis that accompanies diagnosis for an infected fly is certain death.  That is unless the condition is caught early enough and the correct preventative measures are taken.  In this case the best medicine is one of the oldest remedies around, booze.

The increased alcohol in the fly’s system creates an environment inhospitable for the development of the wasps and the fly lives to eat another banana. This conclusion isn’t a simple conjecture made by the authors of the paper but is actually backed up by experimental evidence.  You can read more about the study in the New York Times article that presented it to the general public.

(I experienced some inconsistencies with the first link so if that doesn't work try this one from the Huffington Post.)

What is amazing to me is that the defenseless flies found a solution to their parasitic problem.  Of course flies don’t create committees around public health or engage in research to find cures to diseases. Flies main concern (concern is probably to anthropomorphic – instinct is probably better) is the same as all other organisms - live and reproduce.  Just like every other organism the solution comes from the variability that is already present in the.  Variety results in some individuals being more fit to survive and ultimately those fit individuals pass on their genes to their offspring. 

If you are reading this and are suddenly experiencing déjà vu it is probably because I keep coming back to this point.  Populations are made up of individuals and those individuals are all different.  It is the presence of these differences, and the realities of limited resources, that drives species to evolve. But where does this variability come from?

The answer is that, just like the flies, we are all mutants. We are all X-Men, mutated at random and against our will or control. We are mutated without our knowledge and without knowledge of the consequences.  Though we can’t shoot laser beams out of our eyes or move metallic objects with our minds, the collective mutations of ours, and every species, have shaped us into who we are today and have given us the super power of survival.

The Essentials: The Dawn of Dogs - Artificial & Natural Selection

Announcement:  I'm adding another topic to the list of typical evolution topics. New topic: What is survival and who are the fittest?

There are a lot of different types of dogs. Big dogs, little dogs, smart dogs, dumb dogs. Pretty much any characteristic you want in a dog you can get, as long as it already existed in a wolf.  All domestic dogs share a common ancestor with wolves. The story of early dog domestication from wild wolf relatives is pretty interesting and has close similarities to the natural selection process that drives evolution.  Before getting into the dawn of the domesticated dog age, a review of modern breeding basics will prove helpful. 

The methods for creating, and refining dog breeds are pretty straight forward. If you to want to breed a certain shape, size, or characteristic into a dog you simply faithfully select for that trait from generation to generation and allow that trait to accumulate more and more in the individuals of subsequent generations.  As an example, let's say you want to develop a really fast dog.  To get thing going quickly you could start by finding a pair of relatively fast dogs then mate them.  However, while pre-selecting for speed in the founding generation will surely help in your doggie development duties, it isn't necessary. To end up with faster and faster dogs you just have to choose the fastest dogs in each generation and continue to pair them with other fast dogs.  Following this simple method will result in faster dogs.  (Real breeders, those who are careful, keep detailed records of lineage in order to prevent family lines from crossing their own paths.  Aside from the cringe factor, inbreeding has some serious and negative genetic consequences that are worth the effort to avoid.)

Variety truly is the spice of life

Artificially selecting for particular traits has produced an incredibly wide variety of dogs but the key to the possibility of selective breeding is that there is inherent variety in every population of dogs.  Every litter will have slow, average, and fast dogs.  This universal variability is true for any population and isn't limited to speed.   Every trait imaginable is variable and is therefore selectable. This is one of the basic, yet revolutionary ideas Darwin described as he laid out his case for evolution.  Variability occurs naturally in populations and variability provides the raw materials for breeders, and nature, to select from.

Variability is what allowed dogs to be domesticated in the first place.  As I mentioned above all domestic dogs are descended from wolves. So what crazy breeder mated wolves and selected the ones most willing to wear sweaters and chase after tennis balls?  The easy answer is there was no breeder.*  The more tricky answer is that the wolves actually selected themselves for domestication.   

This may seem like a crazy idea but it is true and it all connects back to variability in populations.  Just as there are fast and slow dogs there are also skittish and trusting individuals in wolf populations.  Skittishness is a survival mechanism for wolves because it keeps them away from danger.   Trusting behavior has the potential to be very harmful.  Imagine throwing caution to the wind when approaching a dangerous animal. In many natural environments the possibility for being killed goes way up if you are too trusting.   However the natural environment is always changing and what was once an undesirable trait can actually become useful if the situation is right.  

In the case of wolf domestication the major environmental change that happened was the introduction of humans.  In the presence of humans a more trusting wolf will have a new food source open up in the form of human refuse.  To a skittish wolf the garbage pile just outside a human encampment would put them too close for comfort but to the trusting wolf the garbage is just in reach.  This extra source of nourishment increases the trusting wolf’s chance of survival and it will therefore be more likely to produce offspring.  Just like the dog artificially selected for speed by the breeder, the trusting wolf will be naturally selected by its increased ability to survive in the presence of this new food source.  As generations pass, the trusting trait will accumulate in the population and due to variability more and more trusting individuals will result. 

Of course the timid wolves haven't gone extinct because the trusting wolves have moved toward domestication.  As described above there are certainly advantages to being timid and the natural environment of the wolves will continue to provide selection pressures to increase their fitness for survival in that environment too.  

Final note: Wolves can't decide to be timid or trusting any more than I could decide to be 6'11 or have blue eyes. In artificial selection a thoughtful breeder chooses traits to survive from generation to generation.  These traits are available for selection because every population has variety.  Natural selection doesn't have a thoughtful breeder but rather uses survival as its selecting agent.  Traits survive on their own (naturally, if you will) if they help an individual survive and ultimately produce offspring.

* The easy answer is there is no spoon, oops Matrix flashback.  This sentence was originally in the essay but a very dedicated focus group was pretty sour on its inclusion so I promptly removed it.

Variability

Not all things are created equal.  Today, in three meals, I had four highly variable species of pizza.

The first pizza was leftover frozen pepperoni. I ate this pizza from a plastic bag as I walked through a frozen urban park. My ungloved hand alternated from transporting slices to my mouth to passing them to my youngest son who was walking just steps away. There was a nice symmetry between the cold pizza and the cold air.

The second set of slices came from our favorite homage to ancient Roman culture- Little Caesar’s.  My usual habit is to render unto Caesar hot sauce, and today was no exception.  The typical Tabasco gave way to the available Frank’s and the results were good.  One of the best things about this meal is its economics. At 65 cents per slice there’s always room for one more.

The third pie of the day was like an American made pickup truck, locally assembled from globally sourced parts. The homemade pizza boasted broccoli, bacon, potatoes, garlic, cheese and, of course, crust. The compilation was dubbed “loaded baked potato pizza”.  This was by far the best pizza of the day for its novelty and the recognition of a concept well conceived and carried out.

The fourth pizza quickly followed the potato pie. I started this apple pie pizza with a fork but promptly found it was best eaten by hand.  The combination of a crunchy and chewy crust made a nice medium for the tart apples and sweet brown sugar to mingle with the home made whipped cream.

The amazing thing about today’s feast is that the four pizzas share a common ancestry with a prototypical pie somewhere in the culinary past.