Evolution and self-reinforcing feedback cycles

This self-amplifying feedback cycle organises the evolution of better-adapted genes over generations through natural selection

Self-reinforcing feedback cycles organise the evolution of life on Earth. Here, I describe several types of evolutionary feedback cycles.

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The evolution of abilities within a species

Each species requires specialised forms of genetic fitness to survive and reproduce, and these requirements differ by sex and life stage. For example, in lions, a mature lioness benefits from abilities including:

strong maternal instincts,
cooperative behaviour within the pride,
efficient hunting ability, and
disease resistance.

This amplifying feedback cycle organises the evolution of better-adapted genes over generations through natural selection. It depends on the selective pressure on a population to adapt to its environment.

In this cycle:

The breeding population consists of survivors from the entire population and tends to have better-adapted genes than the entire population. This tends to result in
the next generation’s population having better-adapted genes than the previous generation, which tends to result in
the next generation’s breeding population having even better-adapted genes.

This self-reinforcing cycle organises the evolution of superior abilities in a species.

The co-evolution of predators & their prey

Another feedback cycle that has contributed to the evolution of life on Earth is the co-evolution of predator and prey abilities, such as those of cheetahs and impala. Over many generations, this cycle can progressively increase the abilities of both populations.


Increased imapla genetic ability.		Increased imapla genetic ability

In this symmetric amplifying feedback cycle :

An increase in the genetic fitness of the cheetah population raises the selective pressure on impala, as the less fit impala struggle to survive, which tends to produce
An increase in the genetic fitness of the impala population, which raises the selective pressure on cheetahs, as the less fit cheetahs struggle to survive, which tends to
Further increase the genetic fitness of the cheetah population.

Cooperative evolution: microbiome

Cooperation also plays a critical role in evolution. For example, the symbiotic relationships between:

Bees and flowering plants
Coral and algae
Cleaner fish and sharks
Humans and their gut microbes.

Consider the coevolution of humans and their gut microbes. Although humans and their gut microbes are distinct species, they form an integrated evolutionary unit, as they depend on each other for survival. The microbes survive into the next human generation through natural childbirth and breastfeeding. Humans benefit from the gut microbiome in many ways, but to keep this text simpler, I will focus only on the microbes that assist human digestion. This is organised by the same amplifying feedback cycle described above for the evolution of abilities within a single species.

In this situation, the “better adapted genes” include:

For humans, the ability to host the microbes by supplying them with nutrition and a stable environment, and
For microbes, the ability to assist humans in digesting a wide range of foods. This ability would have been crucial during food shortages, which were often severe for early humans.

Specialisation in symbiotic evolution

In this symbiotic evolution between humans and their gut microbes, there was:

the initial cooperative interaction between them,
mutual benefit, which increased the reproductive success of both the humans and the microbes.
modification of the environment for the microbes as the human gut became a honed niche for the microbes, and
locked in cooperation, through the specialisation of both the humans and microbes.

The organisation of this specialisation is an example of a complementary system, another amplifying feedback cycle.


Microbes increase their ability to support human digestion of certain foods.		Humans decrease their ability to digest these foods without the help of microbes and become more dependent on microbes.

This is a complementary relationship, an amplifying feedback cycle in which one party (the microbes) tend to increase a specific skill while the other party (humans) tend to lose the same skill.

Mutually reinforcing amplifying feedback cycles.

Here we have a group of amplifying feedback cycles, all mutually supporting one another in the evolution of life on Earth:

The evolution within a species,
The co-evolution of predators and prey,
The co-evolution of symbiotic species, and
The evolution of specialised cooperation between species.

Here, as in many other systems, amplifying feedback cycles interact and reinforce one another. They sometimes produce extraordinary outcomes, such as the intricate web of life on our planet. At other times, they organise destruction, such as the global warming that now threatens this very web of life in which humans have flourished.

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