Biology Reference
In-Depth Information
CHAPTER 15
Conclusion
Photo © Arpat Ozgul
The story of behaviour and adaptation that we have told in the last fourteen chapters is
inevitably too simple. All the 'ifs' and 'buts' of an impeccably cautious and impregnable
account would have made the topic twice as long and half as easy to understand.
However, we do not want to leave the impression that the ideas we have discussed are
completely accepted by all evolutionary biologists. Far from it, even our basic
assumptions are still sometimes challenged.
How plausible are our main premises?
Selfish genes or maximizing individuals?
Our discussions of natural selection have been phrased in two alternate ways. One way
is to emphasise selection on genes, with phrases such as: 'Imagine a gene for such and
such behaviour; when would it tend to spread in a population?'. As we saw in Chapter 1,
this approach does not imply that there are genes 'for' altruism, spite, long tails or
whatever, but merely there are some genetic differences between individuals which are
correlated with the behaviour or structure in question. The other way is to emphasize
individuals maximising their fitness, with phrases such as 'How should individuals
adjust such and such a behaviour, so as to maximize the number of offspring that they
produce', or by developing evolutionarily stable strategy (ESS) models. As we also saw in
Chapter 1, this approach does not assume that animals are consciously trying to
maximize their fitness, just that natural selection will lead to organisms that appear to
be doing this.
But how plausible are these views, and how justified is it to switch back and forth
between the genetic and the individual level? Obviously the field biologist sees
individuals
Genes versus
individuals
