Author: Scott Newson

Last week, Rosie was talking about how biologists are uncertain about the benefits provided by sexual recombination. Particularly, she said something about how ‘the numbers’ don’t show any benefit to the organism for sexual recombination. If I recall correctly, sexual recombination is crossover (that’s how I’m going to treat it for this post and someone needs to correct me if I’m wrong).

Then, in my computer science class today, we were talking about Stochastic Local Search algorithms, of which Genetic Algorithms are a subset, and the lecture presented the introduction of crossover as the defining factor of GAs. The impression that I got was that, in computer science, crossover was assumed to be beneficial. And since computer scientists are generally good at calculating the generalized efficiency of algorithms, I assumed that there must be some fairly definite benefit provided by crossover, which contradicts what Rosie said about the mathematic benefits of biological crossover not adding up.

If GAs in computer science benefit from crossover and biological evolution doesn’t, then I see three possible outcomes. 1) The analogy between GAs and biology break down in this case – which is the default assumption. 2) The computer scientists haven’t done strict tests of crossover, and it will turn out to be unhelpful, as in biology. Or 3) GAs and biology both benefit from crossover, meaning that there will be mathematical models of the benefit of crossover from computer science which might be able to inform biology.

I have some discussion on these three possibilities. But I’m going to have to hold off for now.

So I spent the weekend making a computer game with a bunch of complete strangers. We went from nothing to a finished game in 48 hours, with things like sleep deprivation abounding.

In any case, with computer games on the brain, I am wondering how one might create a fun game that teaches the basic processes of evolution. Not the mechanics and dirty work of getting it running (that’s what engineers are for!), but the concepts it would try to incorporate and the abilities it might try to teach.

Let us assume that we are targeting high-school aged students who haven’t yet taken high-school biology. It is difficult to get them involved in studying (because it’s ‘boring’), but if they are really dedicated to the things they find fun and socially acceptable (like games!). They might already have all the formal biology education they’ll ever get, and know Evolution as ‘one of those theories about how animals, y’know, like, change.’

From the topics that we’ve covered so far, which ones would you consider most important? These can be within the context of biology or any other application of evolutionary theory.

How would you frame this in terms of a game?

(I’ll write my own response to this at some point, but I want to hear what others think first.)

I’ve read the first couple sections, and the section on complexity and nonadaptive processes on page 8600, like Yana suggested. I haven’t read the rest of it.

My first impression was a bit of a “well, of course” situation. It makes perfect sense to me that not all changes are adaptive. It certainly sounds like complexity and directional evolution are contentious within the realm of biologists, which is good to be reminded of.

I found the examples of some species becoming ‘simpler’ really interesting. My first reaction was that of “How do we define ‘simple’ and ‘complex’?” It seemed like the argument in the paper was that of species becoming simpler over time showing that complex isn’t allways better. The examples being salamanders losing their legs and vent-worms going from having two opening to having one. These examples seem to be an assumption along the lines of the ‘if it looks like us it is complex’ complex. What if surviving with no legs or no mouth (in the cases of salamanders and vent-worms respectively) is ‘more complex’ somehow. For example, one might need a bi-directional digestive tract to deal with having just one opening, which takes a very complicated gut to deal with things. I can’t say if this is the case or not, but I am uncomfortable accepting the assumption that X change is a ‘simplification’.

Another question I have is based on the following statement:

“However, the effects of mutation and recombination are nonrandom, and by magnifying the role of chance, genetic drift indirectly imposes directionality ….”

Would someone be able to explain how mutation and recombination are nonrandom? I thought that they were by definition random events that were then selected for/against/neutral.

One last thing I’d like to propose is that maybe a better explanation for the survival/fitness of complex organisms can come from their relatively long life instead of them being better replicatiors? If complex multicellular organisms are not as good at replicating, maybe they just hang around because they take longer to be killed off?

-Scott