Evolution is a complicated business. At the simplest level, organisms accumulate mutations that either help or hurt their chances of reproduction. Over time, the helpful ones accumulate in order to give the organism the best fit possible to its environment.
Many experiments have been conducted on this basis, both in the lab and in computer simulations. Taking mutations one step at a time can be helpful to lab experiments because sequencing DNA, applying mutations, examining results and making sense of it all is a time consuming process. And it’s a messy one that gets really complicated really quickly if there are too many variables.
However, computer simulations don’t have such restrictions.
So it is with a computer simulation that Michigan State University researcher Bjorn Ostman decided to take a different look at evolution. In his model, several mutations occur at the same time and can enhance each other’s effects, single mutations can affect several different characteristics, and harmful mutations can take hold.
This is a much more realistic look at the complex web of evolution. In his computer model, Ostman controlled two different variables – the total number of genes that interact with each other and how many other genes each individual gene can affect. As the two variables change, so does the 3D representation of fitness landscape.
A fitness landscape looks like a range of mountains with the peaks representing good fits for an organism in its environment. When mutations take an organism to a peak, it flourishes. However, in order to get there, it must make it across valleys where its reproduction rate isn’t so hot. Sometimes one amazing mutation can get an organism to a peak, but more often it takes several small ones working together, accumulating or enhancing each other to get there.
According to the model, the best fit and most progress is made in a moderately “rugged” landscape, where the peaks are tall, but not too tall, and the valleys deep but not too deep, and there are a decent number of them available to sit on top of before hitting the highest peak available.
What’s more, the simulation showed that mutations that negatively affect an organism’s chances of reproduction are just as important as the ones that help. It’s a healthy mix of the two that gets an organism across the valleys and to the peaks.
This may seem counterintuitive, but it makes sense if you think about it. A really awesome mutation might be necessary in order to overcome a slightly bad one. Or a mutation needed to overcome a bad one might enhance or work well alongside of another.
If only beneficial mutations ever made the cut, the human body would look much different. For example, it’s not exactly beneficial to have images come through the lens of your eye upside-down, but they do. It also kind of sucks to have the optical nerve pass straight through your field of vision, giving the hindrance of your blind spot. But hey, it works.
Even nature’s mistakes can be beneficial to its creations.