One definition of intelligence is that it is the ability to communicate, learn, and solve problems. Intelligent organisms apply knowledge to manipulate their environment to improve the survival and reproduction of individuals, groups, species, and ecosystems. Life depends on cooperation, not competition. Mutually beneficial symbiotic relationships exist throughout the biosphere. Plants and animals don’t exist in isolation, but as part of a superorganism or holobiont that also contains microorganisms in a microbiome1. This includes the human body, which is an ecosystem that is part of the global ecosystem. We can be thought of as “super organisms” or holobionts with a hologenome. We have a brain not only within our skulls, but in our guts – the enteric nervous system2.

Even though viruses are usually thought to be bad for human health, those that infect bacteria (bacteriophages) help control the populations of potentially harmful bacteria. Moreover, there are parts of our DNA that are mobile, or transposable. These transposable elements are descendants of ancient retroviruses that infected our ancestors. Retroviruses (like the SARS-CoV-2 virus that causes COVID-19) have RNA that is reverse transcribed into DNA when the virus is replicated. That is, normal transcription is when DNA is transcribed into RNA. Reverse transcription is when RNA is transcribed into DNA.

One class of retrotransposon is called L1 (Long Interspersed Nuclear Elements-1). Retrotransposons are important in the healthy development of the human brain, in which new neurons are constantly being made. They are active in the hippocampus and caudate nucleus and may account for many of the differences in identical (monozygotic) twins. Retrotransposons are also important in generating new neurons in the hippocampus throughout life. On the other hand, L1 insertions occur in genes that are commonly mutated in cancer. So, viruses and bacteria are important for human health and intelligence. Viruses are not alive and are not intelligent by themselves. Bacteria are alive and have many of the skills that are often attributed to intelligence.

Bacteria (Prokaryotes) communicate through quorum-sensing, chemotactic signaling, and plasmid exchange. Plasmids are small circular pieces of DNA that are separate from chromosomal DNA. Bacteria can cooperate and self-organize into highly structured colonies that fit into ecological niches. They use signal transduction networks and genomic plasticity (the ability to change in response to changes in the environment) to create a language for communication. They interpret chemical cues, exchange chemical messages (semantic), and have dialogues (pragmatic). The identity of a colony emerges from this communication, which enables intentional behavior (such as pheromone-based courtship for mating), purposeful alteration of colony structure (to make fruiting bodies), decision making (to sporulate), as well as recognizing and identifying other colonies. These are characteristics of bacterial social intelligence 3.

Single-cell Eukaryotic microorganisms in the kingdom called protists also exhibit intelligent behavior 4. For example, the unicellular aquatic protist Physarum polycephalum is a model organism for studying learning. It can be taught to solve problems. It can find its way out of a labyrinth and learn how to ignore repelling conditions when it is associated with a reward such as nutrients. Moreover, learning and memory do not require a central nervous system, as demonstrated by intelligent octopi, P. polycephalum and even plants.

Plants seek out light and forage for nutrients. They avoid competition, form mutually beneficial relationships, and make complex decisions. These behaviors demonstrate phenotypic plasticity. This includes directed growth, differentiation, and modifying their environments to benefit the niches into which they fit. Plant cognition is manifested by their ability to manipulate the environment to enable optimum metabolism and increased survival. Plants communicate, in part, through airborne biogenic volatile organic compounds (VOCs). The emission of VOCs can follow an attack by an herbivore or by other stress. The plants adapt and adjust their phenotype to develop defense mechanisms. Communication also takes place underground as their roots interact with mycelial networks of mycorrhizal fungi5-6. About three trillion trees on Earth survive through symbiosis with an underground network of fungi7. Scientists have mapped a wood-wide web on a global scale, using a database of more than 28,000 tree species living in more than 70 countries.

At the same time, plants and insects communicate, with plants being able to influence the behavior of their insect partners using biochemicals8. Plants communicate through underground fungal networks by emitting volatile organic compounds that travel through the air. The fungi form thin threads (mycelium) that spread through the soil and link the root systems of different trees. This network enables the transfer of essential resources like carbon, nitrogen, and water between plants, so they can support each other.

Some trees can recognize their own offspring and send them more carbon and nutrients, increasing their chances of survival. These VOCs can lure predators of the pests (such as birds to aphids). Some VOCs serve as a warning signal to nearby plants, causing them to produce defensive enzymes or chemicals. can also use electrical signals to communicate danger or environmental changes. This is like a nervous system. They are also transferring portions of their DNA to other species. This produces plants that are resistant to pesticides. Trees in rainforests can stimulate the growth of specific fungi that are toxic to non-native species. As a result, crops that humans try to grow after clearing parts of a rainforest often do not grow or survive very well.

The flow, perception, integration, and storage of environmental information allow plants to adapt and respond. They can attack herbivores while integrating past experiences and environmental cues that help to predict future conditions. The predictive value of environmental information and the costs of acting on false information are important drivers of the evolution of plant responses to herbivores. Defense responses enable plants to prevent the potential costs caused by acting on false information. The priming mechanisms provide short- and long-term memory. By one definition, plants are intelligent. That is, intelligence is a measure of “an agent’s ability to achieve goals in a wide range of environments”. The agent does not need a nervous system and even applies to artificial intelligence9.

Plants are also holobionts that contain their own microbiomes. The phytomicrobiome is essential for the metabolism, growth, health, reproduction, and evolution of plants10. Interactions between plants and their phytomicrobiomes range from associations between roots and microbial communities in the rhizosphere to endophytes that live between plant cells, to the endosymbiosis of microbes by the plant cell resulting in mitochondria and chloroplasts. Mitochondria and chloroplasts were once part of the external phytomicrobiome of the first cell. The endosymbiosis of an alpha-proteobacterium and a cyanobacterium in the ancient holobiome eventually became a mitochondrion and a chloroplast, respectively. These endosymbionts did not replace any parts of the ancestral organism. They did provide new capabilities. This gave the plant cells that had them an evolutionarily competitive advantage.

The phytomicrobiome of modern plants includes parasitic and commensal microbes, as well as mutualists and beneficial microbes, such as mycorrhizal fungi and bacteria. They all help plants grow and survive stress in the environment. The plant host can then alter the abundance and composition of different species of bacteria within the phytomicrobiome. For example, root exudates can select for and promote the growth of beneficial microbes by providing carbon and/or energy sources.

Plants also communicate stress through ultrasound11. They emit high-frequency clicks that we can detect (or hear) using soundproof boxes with microphones designed to capture ultrasonic waves. Thus, they can record the sounds of stressed plants, such as tomato and tobacco plants. Stress was induced by either withholding water for several days or by cutting the stems of the plants. Then, machine learning algorithms were trained to analyze the recordings. This helped the AI learn to identify the specific sounds made by the stressed plants, distinguishing them from background noise. It showed that stressed plants emit a specific type of sound and that each plant species and type of stress is associated with a unique sound signature. The sounds are a form of communication that can signal stress to other organisms. This technology could be used to monitor the health of crops, alerting farmers to problems like dehydration or injury before they become severe.

Similarly, the microbiomes of insects help them survive and thrive. For example, the gut microbiome of honeybees determines their social group12. That is, bees in the same hive have similar gut microbiomes. They help the members of each colony recognize the hive. The members produce specific volatile hydrocarbons and pheromones.

Insects, fish, birds, and mammals have collective intelligence and behavior13. Many of them can migrate thousands of kilometers. Insects can be amazing. Unlike fish, birds, and mammals, individual insects do not make a round-trip journey that returns them to the area from which they departed14. This is intergenerational migration. For example, the monarch butterfly flies south to Mexico for the winter. Then they go north through a process of intergenerational migration, in which successive broods advance northward.

Bees and ants have been civilized for 100 million years. They can organize into large, well-organized groups, make decisions, and communicate through a language that includes pheromones and dances. There are over 20,000 known species of bees, including honeybees (Aphis mellifera). There are over six trillion honeybees in the world. There are as many honeybees that are not domesticated as are domesticated. The total biomass of honeybees is about 2,000,000,000 tons. The total population of all bees is about 20 quadrillion. Most bees are not social but live by themselves.

Thanks to humans, there are far more honeybees that are domesticated than there were before us. They form a large civilization led by a queen. Drones and worker bees take care of the queen and work in factories that produce honey. Our civilizations have been and continue to be tightly linked and are dependent on each other. Humans have domesticated honeybees for about 9000 years. Ancient Egyptians had been keepers who domesticated bees and collected their honey. The oldest honey ever found was 5500 years old. So, humans and honeybees help each other survive and thrive.

Ants have an extraordinary capacity for collective problem-solving. This phenomenon is called ants’ collective intelligence. They collaborate, communicate, and use decentralized decision-making systems that humans can learn from. Ants in colonies collaborate successfully to solve problems efficiently and adapt to changes in the environment. Chemical messengers called pheromones help ants coordinate foraging, maintain the queen and nest, as well as for defense. Ants use a distributed method to solve problems called swarm intelligence. They solve problems by breaking them down into smaller parts. Individual ants concentrate on a specific aspect of the problem. They exchange information with other ants nearby using trails of pheromones that other ants can follow. Ants have shown us that complex problems often can be addressed by decentralized decision making15.

This interaction is even extending into computer science. Algorithms based on the intelligent group behaviors of social creatures are being studied and used for computer-aided optimization. Algorithms for search, optimization, and communication are being developed by simulating various aspects of the social life of honeybees. For example, queen bee evaluation can improve the performance of Genetic Algorithms. One of these evaluation methods can be used to design DNA sequences using a Bee Swarm Genetic Algorithm16.

Human technologies, from beekeeping to predicting weather and climate change, to optimizing the efficiency of sustainable energy, increase our ability to survive, thrive, and evolve – provided we can control them. This includes artificial intelligence (AI). It started as an efficient way of performing a relatively simple task17. It was based on rules or instructions given by humans. For example, it can control indoor environments automatically. It grew into context-based AI. It evaluated and learned from environmental changes, user behavior, and historical data. AI is used to help tailor news, entertainment, and advertising to each person’s individual needs and desires.

AI became capable of exceeding human capabilities in some areas or domains. For example, IBM's Watson can analyze large amounts of medical literature and patient records to provide insights or even potential diagnoses. DeepMind’s AlphaGo was even able to master the ancient game of Go. AI is now in stage 4, reasoning AI. It can mimic the thought processes of humans. Chat GPT, Perplexity, and other platforms use a large language model to answer questions that users ask. These platforms can write books and create art. Another example of stage 4 is the development of autonomous vehicles, which may change society as much as cell phones have.

Perhaps more impressive is the newly introduced AI Scientist18. It is the first fully automated and scalable pipeline for doing research. It develops an idea or testable hypothesis when given a general direction and a simple initial codebase. The AI Scientist does a literature search, plans experiments, modifies and iterates them, writes a manuscript, and even performs peer reviews. The AI Scientist can run in an open-ended loop, building on its previous scientific discoveries to improve the next generation of ideas.

So, intelligence exists throughout the biosphere, Mother Earth, or Gaia. It continues to grow and evolve. Some people even imagine a world in which computers and other machines become self-aware and develop consciousness. While some look at this as an existential threat to humanity, others imagine a more positive future. Perhaps our AI-powered machines can develop a consciousness while learning from humans and other organisms. Perhaps they can share this consciousness with all sentient organisms to build a harmonious humanity and truly deep ecology.

Notes

1 Dietary fiber, the gut microbiome and health. There is an undeniable link between the brain, the gut and the immune system on Meer.
2 Our second brain. The enteric nervous system and gut microbiome on Meer.
3 Bacterial linguistic communication and social intelligence on Trends in Microbiology.
4 Learning in the single-cell organism Physarum polycephalum: effect of propofol on International Journal of Molecular Sciences.
5 Consciousness and cognition in plants on Wiley Interdisciplinary Reviews: Cognitive Science.
6 Las plantas se comunican a través de una red subterránea de hongos on Meer.
7 Mycorrhizal networks facilitate tree communication, learning, and memory on Springer.
8 Induced resistance to herbivory and the intelligent plant on Taylor & Francis Online.
9 A collection of definitions of intelligence on Frontiers in Artificial Intelligence and Applications.
10 Plant holobiont theory: the phytomicrobiome plays a central role in evolution and success on MDPI.
11 Sounds emitted by plants under stress are airborne and informative on Cell.
12 The gut microbiome defines social group membership in honey bee colonies on Science Advances.
13 Collective cognition in animal groups on Cell.
14 How and why do insects migrate? on Science.
15 Ants’ Collective Intelligence: What Could We Learn? ResearchGate.
16 Principles of cognitive biology and the concept of biocivilisations ScienceDirect.
17 10 Stages of AI: A Journey from Simple Rules to Cosmic Consciousness on Medium.
18 The AI Scientist: Towards Fully Automated Open-Ended Scientific Discovery on arXiv.