Weather Forecast: Sharks

Much like the weather, natural selection is always happening. And much like the weather, we don't notice it until things start to change. 

Picture an average winter day. It doesn't matter what you picture - just pick something. I think of clear skies and snowy fields, just cold enough to make me want some hot chocolate. What I don't picture is below-zero weather bad enough to make me type this while laying under three blankets. 

But here we are. 

Natural selection is a lot like the weather. Weather happens all around us, all the time - but it's so subtle that we don't really notice until something makes an abrupt change. If the weather is like natural selection, then climate change is like evolution. It seems random, startling, and abrupt - until we look closer. 

Of course, not all weather is destined to lead to climate change. Just like not all natural selection is destined to lead to evolution. Weather can hold steady patterns for hundreds of thousands of years, each season reinforcing the rhythm of small changes. In the same way, natural selection isn't always gunning for some new and outrageous design - sometimes it simply holds steady, reinforcing the pattern that already works so well. 

I mean, look at sharks. 

https://www.mendotraintony.com/sharks-along-the-mendocino-coast/

God, I love sharks. Sharks evolved around 450 million years ago ("Geologic Time", Martin). Four-hundred and Fifty. Million. Years. That's 200 million years before the first dinosaurs. And yet the earliest sharks looked surprisingly similar to the ones swimming our modern oceans. 

https://www.nhm.ac.uk/discover/shark-evolution-a-450-million-year-timeline.html

If you showed that to me and said "Wow, look what some scientists saw off the coast of California!", I wouldn't think anything of it. Except maybe to make fun of its derpy little face...

Anyways, my point being, sharks haven't changed much over 450 million years! They've diversified and evolved into specific niches, but their plan-of-action for survival is pretty much the same: swim around and eat things. If you want to watch shark evolution, you're going to be waiting for a long time. 

But we're not talking about evolution. We're talking natural selection. And even though sharks haven't evolved much lately, natural selection is still in action. Because sometimes, like the weather, natural selection doesn't have big and dramatic events; sometimes it just maintains the status quo. 

Natural selection has made sharks into something simple and efficient. That countershading? That big propelling system and that pointed nose? Those traits work. Sharks aren't evolving, because they don't need to; natural selection has already put them into a well-adapted form. All selection is doing now is reinforcing that form, tweaking it by little bits, making it better but really not changing much at all. 

Because it works. 

Natural selection isn't striving towards some higher goal. It's not trying to make tool-using or bipedal sharks. Natural selection meanders towards forms that work well in a specific environment, evolving over time to make an organism really good at surviving and reproducing. And if natural selection has 450 million years of finding a good form, that form is going to be pretty. damn. good.  

Sharks don't need to evolve, they just need to maintain their current form. So that's what natural selection is doing. 

Of course, there are other forces of change outside of natural selection. Anything that alters the genes frequencies in a population is one of those "forces of change". Big disaster kills off a bunch of sharks? The sharks that are left might randomly have smaller fins. Then all the offspring of the survivors will also have smaller fins. It's not natural selection, it's just chance. This is called the bottleneck effect. Chance also plays a factor in something called genetic drift - where some traits become more common out of pure coincidence, and not because they're better for survival or reproduction. And let's not forget the importance of choice: sexual selection can also lead to evolution - even evolution that seems counterproductive! Colorful birds are way easier for predators to spot, but boy howdy do they get the ~ladies~. All of these forces can cause change, and even lead to evolution, despite the fact that they're not events of natural selection and don't always lead to better-adapted forms. 

Long story short, things in nature aren't simple. We can't always see what's going on right in front of our eyes - but that doesn't mean it's not there. You don't need massive change for something to be happening. So go outside and open your eyes - and try to see not just the big things, but the small things too. 

Or maybe don't. It's like, -20 F out there.