Home > What is science? > On Technobabble in Evolutionary Theory Part Two

On Technobabble in Evolutionary Theory Part Two

Last week I discussed some of the most controversial words in the public view of science today. Chief-most: Evolution and natural selection. I hope that I cleared up a little confusion and hopefully educated a few people. Some seemed to enjoy the blog post enough to think it deserved a like so following that and the fact that it’s 3 o’clock in the afternoon on the day I’m supposed to publish this, I’ve decided to rush through and write part 2 for this week. I don’t know if I’ll need to do a part 3 or if I will think of adding anything so for now I’ll assume this will be a conclusion of the previous blog.

I’m going to focus on some of the other mechanisms for evolution and use them to explain evolution in a more accessible manner that also gives people an idea as to why it is both random (In the sense of being directionless) and purposeful (That it can create complexity and apparent ‘design’). So to begin this, we must cover the ‘basic’ concepts of randomness and design.

Randomness is a part of probability statistics. Probability statistics being two long words that includes the word statistics can terrify people but it can be quite easy to understand. Fear not, I’ll leave out the numbers for today (Numerophiles, fear not, I’ll do a post for you at some point) The basic idea of randomness in evolution is that mistakes can occur in the copying of genetic code and these mistakes are undirected and random. The idea being that one mistake is roughly equal in occurrence as any other.

This random variation is required to start off the engine of evolutionary change, this is the spark plug of evolution. It ignites the fuel which is variation and the engine of natural selection uses this to generate forward momentum. The thing is, while natural selection generates this forward momentum, there is some steering in our ‘car of life’ and that determines where on the ‘map of possibility’ we will end up. Allow me to explain, The engine of natural selection attempts to ensure that whatever our organisms are supposed to do, they do it as well as possible (This is the forward pushing of the engine), however the direction they travel is dependent on what is steering and it’s not always purely one single trait that is being developed by natural selection to it’s extreme and all other traits are secondary.

For example, a bird which wishes to fly would remove as much weight as possible, brains are heavy, so a bird optimised for flight wouldn’t have a brain (Please, no bird-brain jokes). However, a bird without a brain wouldn’t be able to do much without it’s central control for it’s nerves and endocrine system, so a bird has to ‘steer’ for optimum flight capability AND ability to think.

There are other things which can also steer and can even appear to make things go in reverse. These are the sorts of things I’m going to discuss in the rest of this blog: To begin, with, the fun one, or rather, the one with the name that makes it seem fun but actually is all about limiting fun to some special ones with special characters. Yes, I’m talking about sexual selection. This is your peacock, your birds of paradise, your deer antlers et.c., et.c. The idea being that a trait in a particular sex (such as a peacock’s tail) is selected for by preference of the other sex, that is, the peahen loves a man with a big bushy tail and so mates with the peacock with the largest most impressive tail. This is taken to extremes with some species such as the peacock where it appears to be a severe handicap, but the woman gets what the woman wants. Even though a large tail can mean a shorter lifespan than a short tail, it means more snu snu so the big tailed peacocks produce more offspring.

The next one I’ll cover is what happens when you don’t steer at all, it’s called genetic drift and it happens when there isn’t much pressure to direct evolution down a particular path. A good example of genetic drift is the lobed vs unlobed ears of humans, some humans have flappy lobes on the bottom of their ears (Where the earring attached) some people have attached lobes (Have a look at this for pictures if you’re unfamiliar) The idea being that some traits are neutral and give no benefit or disadvantage and so the genes mutate and increase and decrease with frequency independently of survival rates and by chance some versions may increase in frequency. (Note: this is not the main force of evolution, it is likely genetic drift only occurs rarely on very few genes so to say that this in any way explains evolution as an entirely random process at best shows a severe misunderstanding of the point and at worst a deliberate and malicious attempt to misinform)

Another mechanism I’ll attempt to explain this week will be phylogenetic inertia, this is where the evolutionary history of a species maintains a stable mechanism. For example, horses have fused their fingers and wrists and toes and ankles respectively into a line of bones shown here in figure 1. This is very good at what it does and is maintained but what if the horse needed to do something different? It would be difficult for a horse to evolve the fingers and toes required to construct a hand like a human’s with a thumb for grasping because the phylogenetic inertia keeps the horses hoof as it is. Indeed, even with 5 digits, there is more than one solution to the grasping problem, as shown by the panda’s thumb. Which is often cited as a wonderful example of our next word:

Exaptation is where something which evolved for one thing is co-opted for use as something else. The sesamoid bone of the panda evolved for the support of a tendon within the foot, it was used by the ancestor of the giant panda to pin bamboo shoots against with it’s fingers, allowing it to grasp them. This in time selected the bone for use in this new function. Another example is the ear bones of mammals which were originally jawbones, as evidenced by the study of embryological development where the bones form as part of the jaw before moving up into the skull. Or Jawbones themselves which form as gill arches which would have originally supported the gills of our fishy ancestors before being used to support the mouth and in time hinging so that the mouth could open and close.

Now, I’ve sort of just thrown out all of these mechanisms which have been observed in nature to select particular traits in some, suppress traits in others, but why? What use is saying that ‘natural selection isn’t the only mechanism’, what use is saying ‘Darwin didn’t know everything’, why say ‘evolution is not just natural selection’? Because it’s not. If we want to understand the world we live in then we need to understand all of it and as I believe I said last time, Darwin wasn’t a prophet, he didn’t know everything and it’s important to show that we’ve got somewhere in our understanding of life since him.

All of these mechanisms show how it’s not just about who lives or dies in evolution, it isn’t just ‘every man for himself’ sexual selection is just one form of selection that demonstrates a species can select itself towards particular traits. Humanity has selected towards traits that involve cooperation within a group (Intergroup competition still exists and has always existed of course) and this is something which defines humanity. Removing religion won’t remove humanity from humans (I would personally argue it would give us a bit more humanity but that’s an argument for another time). Evolution doesn’t mean that we are in a dog-eat-dog world, it means that those that die without leaving as many descendants as others will eventually be wiped from a population.

I will conclude with the point that humans are more in control of their environment than ever before and we can effectively decide to remove a lot of the natural selection from our populations should we wish, we can make sure that people don’t die off from other things. I, for one, would be very interested to see what would happen if humans decided to select for traits which reduced world suck and increased awesome. I mean, we could totally select for people who were good with genetics and get dinosaurs in space even sooner. I hope I didn’t ramble too far from the point, see you next week.

References

Potholer54: The car metaphor is a more in depth version of his metaphor from a video on evolution from his youtube channel (If I remember correctly at least).

Advertisements
  1. September 25, 2013 at 12:12 am

    Seriously, thank you so much for explaining phylogentic inertia in a simple way. I have been searching for a simple, yet well thought out explanation for the past week and have been coming up dry. Thanks again!

    • November 28, 2013 at 8:38 pm

      I feel bad that your comment is the only one which I haven’t responded to. This is a terrible oversight since your stumbling on this blog and decision to write a positive comment made me want to start blogging again after having let it slip out of sight. Anyway, credit really should go to my tutor at university who helped me understand phylogenetic inertia for myself. I’m glad the post helped.

  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: