Why this Page?

We talk about evolution in a strange way, using analogies and expressions that are imprecise at best. This is probably why we have difficulty understanding it. Let’s explore.

How Evolution works

It is already very much wrong when we say animals and plants adapt to their environment. They do not. What really happens is:

an animal or plant produces offspring, it “replicates”,
the child replicas are close to the parent original, but they are not always exact copies,
some of these copies survive and replicate again, others die before they can do so,
which copies replicate and which die is decided by the environment: those copies whose differences from their parents make them less well adapted to the environment have a higher probability of dying, those whose differences make them better adapted get a higher chance of surviving to replication age. That is selection of the fittest.

But individual animals or plants do not adapt to their environment; they don’t change genetically during their lifetime.

A negative mechanism

Selection acts mainly by preventing some copies to reach replication age.

Nature does not produce positively adapted offspring, it kills offspring that is badly adapted.

That's a pretty negative mechanism.

Non-optimal

Offspring that is not a perfect copy of the parents is different in some random way. If the differences are not lethal, then they may be passed on. They may also just be irrelevant to survival.

Useless characteristics may then come into existence for which there is not much negative selection before replication age. These traits then do replicate, perhaps for a long time. Sometimes a new trait may give such an advantage that other, indifferent or even negative traits are not removed by selection.

For example: mammals have eyes whose receptors are “inside-out”; the nerves carry the visual signal from the front of the retina and then go back out in a bundle through the rear of the eye (the reason for the “blind spot”, where all those nerves traverse the retina). Therefore mammal eyes are not as good as they could be. Mammals can’t see in the ultraviolet as birds can. Your retina is also prone to becoming unstuck, but this happens usually only after reproduction age hence this eye-disadvantage does get reproduced, but although it is bad, it does not prevent you from having descendants.

Mammals survived despite relatively bad eyes because they had other, more important advantages.

Speed

Evolution works from one generation to the next. The speed with which change occurs depends then on two major factors:

the length of a generation: the shorter, the more possibilities to adapt are generated in a certain time. Elephants and humans take a long time between generations; fruit flies and mice have short generations. We would expect the latter to adapt faster to changing environments.
the amount of variation in each generation: if successive generations are always almost perfect copies there is less chance to adapt better than if many variations occur each time.

The advantage is to the organisms that are able to adapt fast, i.e. a fairly high mutation rate and a short life cycle. That is what allows bacteria to become resistant to antibiotics in our lifetime, and why it is easier for farmers to select for better vegetable varieties than for better trees.

These two factors tell us something important about the crisis of global warming (euphemistically called “climate change”). It is true that in the past there were periods when the climate of our planet was much hotter, but animals and plants still thrived. However the changes in temperature happened over millions of years, and life had ample time to adapt. The sudden change we witness today is far too fast for evolution to keep up, except perhaps on those organisms that have very short generations.

Problem: while many variations per generation allow for faster adaptation, it also means more bad copies which are not able to survive at all. There must be near-perfect copying for each generation to be able to survive.

A dynamic situation

The environment changes: ice ages come and go, new predators move into the habitat. Animals (and plants of course) are never completely adapted to their environment. To say that in nature everything is marvellously adapted for the best is therefore nonsense: organisms may be quite well adapted, but they can always improve. The situation is dynamic, the goal is always moving.

An unfortunate choice of name

The biological evolution mechanism is also called Darwinian evolution. Its main characteristic is removal of unfit copies from a large pool of slightly differentiated copies. It is a negative mechanism: it weeds out the bad.

The reason for this page was my dissatisfaction with the words we use to talk about evolution. I find that using the name “Darwinian evolution” contributes to the confusion: attaching someone's name to it makes it sound as though there is a choice of evolutions that the user can shop for. But this is not so: there is only one kind of evolution at work in nature. Darwin (and Wallace) just happened to be the first people to describe it.

See the page about communicating science.

Discussions…

I am totally convinced that evolution explains all of biological life as we see it on Earth. The evidence is overwhelming. Very good explanations and description of evidence can be found in the books of Richard Dawkins and Steven J. Gould.

Evolution is also mentioned as the “normal” way of change in other areas: the economics of the free market have characteristics similar to evolution; technological advances do too, and recently programming has been done by “genetic algorithms” which reproduce and adapt to the solving of a problem.

Some people still have trouble with the reality of evolution, notably creationists and advocates of intelligent design. It’s interesting to read the transcript of the 2005 Dover trail, and it is equally interesting to reflect upon the nature of “design” itself.

Is it fundamental?

Are we stuck forever with evolution? Are there other mechanisms for progressing towards a goal?

In other words, is evolution a constant of Nature built into its very mathematics, coming out beautifully in biology, but in fact also unavoidable anywhere else, in any changing information system?

I tend to think so.