In most species (a species is a group of individuals capable of producing fertile offspring; like snakes, lions, humans) there are always more offspring born than can survive to adulthood and reproduce. Darwin said there were two reasons for this: (1) Since there is limited amount of resources available (like food, space, mates) there is competition between individuals for these resources and (2) Since the environment changes over time and from one region to another, there are threats (predators, change in climate, isolation, diseases, change in the physical environment) to the children’s survival and the reproductive success.
Within a species, there is an enormous amount of individual variation. No two individuals of the same species are alike in their anatomical structure, physiology, or behavior (we’re not an exact copy of our parents).Individuals vary in their cell structure, fighting ability, and social skills. Variations make every individual unique and that variation must in some way be heritable otherwise children wouldn’t resemble their parents more than they resemble other individuals.
Species change. New ones arrive. Others go extinct.
Darwin called his principal natural selection. Any slight variation in traits that gives an individual an advantage in competing with other individuals of the same or different species or in adapting to changes in their environment increases the chance that the individual will survive, reproduce, and pass along its characteristics to the next generation. Maybe they have greater resistance to disease, or can run faster, or survive climate changes better.
Darwin used the word “selection,” but nature doesn’t care who gets selected for survival. Evolution has no goal. So how and why do we evolve the way we do?
We are driven by our need to avoid pain (and punishment) and a desire to gain pleasure (and reward). Evolution has made any behavior that helps us survive and reproduce feel pleasurable and rewarding. Behavior that is bad for us feels painful and punishing. Feelings of pain and pleasure are useful guide to what is good or bad for us. If we eat, we feel pleasure. If we starve ourselves, we feel pain.
“Human beings are pulled forward toward and by nature.
They seek pleasure, where they flee from and reject pain.”
- Epicurus (Greek philosopher 341-270 BC)
Harm avoidance first. Our brain is equipped to register pain more sensitively than any other emotion. We remember negatively arousing stimuli even better.
The fear of loss is much greater than the desire to gain. Research shows that we feel more pain from losing than we feel pleasure from gaining something of equal value and that we work harder to avoid losing than we do to win. That we pay more attention to possible losses than gains makes sense.
Our aversion to pain also encourages a certain human behavior: to take the most rewarding view of events. We interpret choices and events in ways that make us feel better. We often prefer to hear supporting reasons for our beliefs; think of ourselves as more talented than others, and make the best of bad situations.
“Good and evil, reward and punishment, are the only motives to a rational creature:
these are the spur and reins whereby all mankind are set on work, and guided.”
- John Locke (17th Century E Philosopher