Evolution – aiming to an objective?

This is a translation of Bastian Greshakes article “Evolution – auf ein Ziel hin?” in the German blog posts


 Werner Arber is at the Lindau meeting for the tenth time this year and again he has been giving a lecture. His topic for this year’s meeting was “Genetic and Cultural Impacts on the Course of Biological Evolution”and he mingled notorious information with little new one.

I’m full of bacteria. And most of them are friendly. Only some become pathogens.” – Werner Arber, 2010

Because who watched – like me – some of his older lectures in the Lindau media library, can see the main features of this lecture yet in the 2007 lecture «Darwinianevolution as understood by scientists of the 21st century».

What of course doesn’t turn the lecture itself bad at all. It’s worth yet for the hand-drawn foils. And yes, by that I mean those sheets that you put on an overhead projector to throw them on the wall. Completely independent from beamers and laptops (and eventually missing adapters that you need to attach the laptop to the beamer.)

And that not just on principle but because Arber uses the advantages of such a projector: They give him the oppurtunity to hold his lecture relatively free without having to plan every detail precisely. On overhead transparencies you can draw something even during the lecture, in powerpoint slides this possibility is restricted.

Arber first explained in his lecture that genetic variation is the driving force behind evolution. Without variation there can be no selection which he called trend-setter of evolution. I find his choice of words is an infelicity of expression. His term can be understood in a manner that evolution has an target that it aims for. And from there it is yet a tiny step to postulate that there is intelligent design.

But of course Arber didn’t mean it that way, because the direction is always just the “best adaption possible” through which then selection is achieved. He also addressed the issue of mechanisms that ensure genetic variation. Genes are made of the region in which the later gene-product is encoded and the control-regions (which don’t neccessarily need to be in spacial proximity).

A changed sequence in the gene is thereby – at least with a modern view – the mutation. In classical genetics you just call it a mutation if there is an altered phenotype that is passed on to further generations. But luckily we’re not stuck in classical genetics. Such mutations can then either be harmful (which is mostly the case), have positive impacts (the rarest case) or just be neutral, which means they have no effect on the success of reproduction.

Next to mutations also the recombination of genes (entire stages are copied, deleted etc.) and the horizontal gene transfer enrich genetic variation. For the microbiologist Arber the latter case is of course especially interesting: In horizontal gene transfer, genes are submitted from one organism to another. And that sometimes even crossing the borders of different species. So far it was common belief that this is only possible in bacteria because they can even perform this step controlled to some extent. But through retroviruses this is potentially possible in any other organism as well. In this context Arber shaped the dictum that we as organisms might not just have one common ancestory but also a common future through the transfer of genes. Afterwards Arber passed on to the genes he calls “evolution genes”. Those cause like restriction enzymes directly a genetic variation or just modulate the frequency with which such variation is caused. 

“Natural reality takes actively care of biological evolution”

 

And this sentence made me listen attentively because again there is such a comparison of evolution aiming in a certain direction or even having intentions. Or wanting to award nature such a purpose. Yet the thought of a second-order-selection is not as incongruous as it seems at first glance. Restriction enzymes exist and they take care of variation and its preservation. Still I would not say that natural reality actively enforces that. 


I find it more likely that in the course of evolution exactly such enzymes were formed. And even if they did not have an aim in the proper meaning of the word they brought their carriers of the gene an advantage in fitness. Variation causes – also if that’s rarely the case – positive changes. And if you have to adapt to changed life conditions it can be an advantage to have variation. If you want to know more about this topic, Werner Arber gave the Lindaublog a great interview in 2009 “Looking back”  and here is a further lecture and an interview with him.