What is natural selection?
It may seem like a silly question.
However, most people are probably more familiar with phrases that have come to represent the process such as:
‘survival of the fittest’, ‘only the strong survive’, ‘it’s a dog-eat-dog world (out there)’,
and the list goes on I'm sure.
Or perhaps you have heard of the Darwin awards, a site that “commemorate(s) those who improve our gene pool by removing themselves from it.”
To be accurate, I would argue these common associations actually refer to a principle of natural selection called gause’s law or the competitive exclusion principle.
Do only the strong survive?
Go to rainforest and you will find yourself in one of the most diverse ecosystems on our planet. Notice anything strange?
If only the strong survive, why is there so much diversity?
Before you think Darwin or Gause
messed up, I will argue there are two important factors to think about not
included in the phrases mentioned above: environmental
complexity and time. That is, society's truncated interpretation is messed up.
What is a ‘resource’?
There is a part of the competitive exclusion principle worth highlighting: the principle states that competitors competing for the same resources when other ecological factors are constant cannot co-exist.
Thinking like a survivalist, the key resources for survival are:
Although fire is not a requirement for wild animals, the others definitely are. Survival is also not always about food. Shelter or spatial arrangement is very important.
For strong competition to occur and cause exclusion or extinction, the key is to think of situations when ALL these requirements overlap.
Some species may rely on similar water and food sources but be spatially separated. To Returning to the rainforest example, stratification results in species that live on the ground while others can live high up in the canopy. Although they may eat similar food, they rarely come in contact.
Within a specific spatial region, different species may then rely on different food sources to avoid competition. For example, different species of birds in the same canopy may specialize in different food sources like nuts and bugs allowing co-existence.
However, the rainforest is an extreme example. What about other environments?
Take a liter of ocean water, for example, and examine it under a microscope. Would you expect there to be a lot of diversity? You might be surprised.
Environments that appear simple may not in fact be as simple as they appear. Gradients of food, temperature, light make subtle spatial differences very distinct especially for microorganisms such as plankton shown above.
Even diversity itself creates complexity due to interactions between species.
Do not judge of an environment by it’s cover.
Currently, factors that allow diversity to co-exist is still widely studied and discussed today (For an example, check out Jeremy Fox's work trying to 'kill' the intermediate disturbance hypothesis).
Now that we have established that strong overlap needs to exist, let’s talk about what it really means to be fit.
How do we define who is strong / fit?
Are you fit? Maybe you go to the gym regularly and you would describe yourself as fit. But, that is not what we are talking about here. Rather than how much you can bench press or your mile time, evolutionary fitness is about population growth rate.
As I mentioned before, the trick is that we need to consider time.
If we consider fitness through time, the focus shifts from a comparison of individuals to a comparison of groups. For example, can you tell me how fit is your family? Said another way, how much has your family grown over the past 1,000 years? Hard question to answer.
To answer this question, you really need to track genetic signals that belong to a family lineage.
A very commonly discussed example you have likely heard of is Genghis Khan’s lineage that is over a thousand years old. Data seems to suggest that 1 in 200 men are direct descendants of Genghis Khan. Besides the fact that Genghis Khan could probably out bench press me, his lineage is also very evolutionarily fit because his lineage displays an exceptional growth rate.
Only the most resourceful over the long term survive?
I think society's interpretation of natural selection and the competitive exclusion principle is a bit too pessimistic. Think of the liter of ocean water; although two organisms competing for the exact same resources cannot co-exist, opportunities to find a niche are numerous.
Although Winston Churchill was not talking about natural selection, I like the use of this quote in this context. It may be a dog-eat-dog world out there but co-existence is possible if you find that little corner of the universe in which you excel.