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

The evolution of abilities within a species

In any species, evolution does not act solely on genetics. Genes, physical capacities, senses such as hearing and sight, cognitive abilities, social behaviours like communication, and—even in some species—technological skills like tool making develop together as an integrated whole.

In early human ancestors, for example, genetic changes affecting hand bones and brain development reinforced one another. As grip strength and precision improved, individuals could manipulate stones more effectively; as tool use became more important, natural selection favoured enhanced brains with planning ability and fine motor control. Over time, these traits co-evolved, each amplifying the adaptive value of the others.

(The untold story of our remarkable hands and how they made us human: New Scientist: 17 Feb 2026)

Every species faces specific fitness demands shaped by its environment, and these demands often differ by sex and life stage. In lion populations, for instance, a mature lioness benefits from a collection of traits: effective maternal instincts, cooperative behaviour within the pride, hunting skill, physical endurance, and disease resistance.

Evolution of the species proceeds through a self-reinforcing feedback process driven by natural selection and natural variation.

	Natural selection: Survival of the better adapted
The entire population		The better-adapted breeding population
	Natural variation

Diagram: The natural selection and variation feedback cycle amplifying the advantageous traits of (1) the breeding population and (2) the next generation.

In this amplifying feedback cycle, driven by natural selection and natural variation:

• The entire population experiences natural selection, so individuals with advantageous traits tend to survive and make up the breeding population.
• The breeding population tends to pass on (1) their advantageous traits, and (2) natural variations, e.g., genetic mutation, to the next generation. Then the cycle repeats.

Both causal links in this cycle only operate intermittently:

• The breeding population will sometimes not be better adapted. For example, a natural disaster could decimate the population and, by chance, leave inferior breeders.
• The next generation will often fail to acquire advantageous traits. Offspring may not inherit the adaptive trait at all, or they may inherit it but die before reproducing. In addition, waiting for beneficial traits to arise—such as through genetic mutation—can pause the cycle. Even once an adaptive trait appears, it may take many generations or intense selective pressure for it to spread widely through the population.

This feedback cycle is a sequence of tendencies, not certainties, and there are periods in which this cycle is not dominant. For example, there are periods in which a species loses abilities or fails to adapt rapidly and becomes extinct. Also, perverse periods in which adaptive change fails to become widespread in the population.

Yet, across vast timescales, this iterative process has dominated. It has generated complex features like eyes and the extraordinary diversity of species on Earth, each with finely tuned abilities and intricate relationships with other species, the web of life.

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 CHEETAH abilities.		Increased IMPALA abilities

Diagram: The feedback cycle amplifying abilities in both predators and prey

Over a period in which this symmetric amplifying feedback cycle dominates:

• An increase in the abilities of the cheetahs raises the selective pressure on the impala and increases the abilities of the impala.
• The more able impala increase selective pressure on cheetahs, increasing the abilities of the cheetah population, and then the cycle repeats.

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 co-evolution 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 pass to the next human generation through natural childbirth and breastfeeding. Humans benefit from the gut microbiome in many ways, but for simplicity, I will focus only on the microbes that aid human digestion. The amplifying feedback cycle described above for the evolution of abilities within a single species organises the co-evolution of humans and the gut microbes.

	Natural selection: Survival of the better adapted
The entire population.		The better-adapted breeding population.
	Natural variation

Diagram: The natural selection and variation feedback cycle amplifying the advantageous traits of (1) the breeding population and (2) the next generation.

In this situation, the “better adapted” includes:

• 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 reduce their ability to digest these foods in the absence of microbes and become increasingly dependent on the microbes.

Diagram: The feedback cycle amplifying the ability of microbes to digest some foods and the human loss of this ability

This amplifying feedback cycle is a complementary relationship. Over a period in which this cycle dominates:

• The microbes increase their ability to digest some foods.
• Humans reduce their ability to digest these foods.

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; for example, global warming now threatens this very web of life in which humans have flourished.

Counselling Pages & References

The introduction to my counselling pages includes:

• Links to the other counselling pages, which include pages describing how this approach relates to other counselling practices and theories, are at the top of the introduction page
• References for all the counselling pages are at the end of the introduction page.

Loaded: 19 Dec 2025: Updated 13 June 2026