On the Origin of Species

On the Origin of Species is the foundational book for modern evolutionary biology that marked a turning point in how we think about the beginnings of humankind.

Before we proceed to explore the laws of natural selection, let’s look at human-induced breeding of certain animals. Various breeds of dogs or pigeons, for example, are the product of human selection.

Let’s assume a pigeon keeper wants to obtain a breed of pigeons with long necks. What she will do is select a couple of pigeons from a bunch with longer necks. After they mate and produce offspring, she will again pick the longest-necked pigeons from among them and breed them again.

After repeating this process for many generations, the breeder will eventually get pigeons with significantly longer necks than those in the first bunch. This process is possible thanks to the rule of descent with modification. According to that rule, parents’ genes are passed down to their offspring – but always with some modification and mixing with their partner’s genes.

We can acknowledge that, in the process of natural selection, nature acts as an “invisible breeder” of the species. However, rather than picking the trait variations based on some arbitrary aesthetic principles (like with pigeon breeding), nature chooses those traits which support the species survival.

The more a specific trait is useful for survival, the more the possessor of that trait is likely to breed. This ensures that the most adaptive traits are passed down to the offspring – and so, the next generations always evolve to be better suited for survival than their ancestors.

Survival-enabling traits are important. But they’re not the only factor which decides about how natural selection will shape the species. Other important mechanisms in play are sexual selection and diversification. A very well-adapted individual, whose genes enable it to thrive in their current environment may still not manage to pass those genes on if it fails to mate. That’s why being attractive to the potential sexual partner is also a key factor in natural selection. Interestingly, the competition in this realm happens mainly between males. As Darwin notes, male are the ones who have to adjust their traits to the liking of the females. The latter, conversely, get to decide which characteristics they value the most in their mates. Consequently, they have an important say in how the species evolves! This is certainly an important point to the ongoing feminist debate. But Darwin was probably unaware of that while making this observation. Another important factor for a species’ survival is diversification. As a population of one species grows, it needs to spread to other habitats in order to simply feed itself. As it spreads, the particular…