Evolution in a (super simplified) nutshell is: descent with modification, acted upon by natural selection.
That is to say, organisms pass properties from one generation to the next via some process or other. This process is never perfect and therefore each new generation of a given organism will differ slightly from its parent generation. These differences will be selected upon by the environment; changes that offer some advantage to an organism in a given environment will eventually spread throughout a population (survival of the fittest).
However, most (significant) modification will be disadvantageous, certainly if change is only achieved by (random) errors in the copying process. This should mean that almost every trial will end in (fatal) error. In that case, even the 3 billion or so years that have passed since the first unicellular organisms appeared on earth would not represent near enough time to produce life as we know it today in all its complex diversity.
A 'recent' discovery in physics helps address this problem; complex adaptive systems self-organise.
A discussion of this phenomenon of self-organisation, and/or complex adaptive systems, is way beyond the scope of this piece - not to mention how monumentally challenging it is to your author's intellectual capacities - so I will just give a (hopefully compelling) example to illustrate the phenomenon.
Consider the termite colony. Termite mounds are built without a site director or a project manager or in fact any kind of management structure. How do all those termites, scurrying around in their own little restricted worlds, so obviously manage to work together as successfully as they do? They, that is to say, the complex adaptive system that is a termite colony, self-organise(s).
This tendency to self-organise introduces another possible source of variance in evolution. The environment selects on these experiments in self-organisation in precisely the same way as it does on the changes in the genetic code of the individual organisms, blindly but steadily (Mother Nature literally takes aeons to realise her handiwork), weeding out that which does not work well in favour of that which does.
All well and good, but what good could all this possibly be to us in software development?
Well, if a few extremely smart software engineers were to get together to see how they could best build good software, they might consider how Mother Nature goes about her work. If it was possible to speed up the process of selection acting upon modifications they might even have been on to something...
Well, a bunch of software engineers did go through an approximation of this thought process, and they came up with... Scrum!
Scrum ( in a super simplified) nutshell is; self-organising units engaged in constant experimentation, the results of which are acted upon by (short) formal feedback cycles at multiple levels
In short, Scrum works because it is a modified copy of how that greatest of all engineers, Mother Nature, goes about her job.