The evolutionary line between health and illness

By Marta Koblańska, September 30, 2025, 17:50 Polish time, Photo: AI-generated neuronal structure, thanks to BrianPenny, Pixabay

Differentiation in neuronal structure within the hypothalamus, as well as modifications in transmission and aggregation of certain molecules, may represent the boundary between health and illness, according to scientists in China.

The structures in the brain, such as various sections, exhibit similarities across mammalian species. Some of these structures are more primitive in shape and function, while others are considered more advanced. These changes have occurred over the evolutionary paths of all species, both those that existed in the past and those alive today on Earth. The primary drivers of evolution include genetics and the environment. Additionally, French anthropologist Claude Levi-Strauss also emphasised the role of group organization, using early human societies as an example.

Leslie A. White, an American anthropologist, pointed out that energy is a major driver of the advancement and thus civilization (that may end in certain circumstances), seeing more and more sophisticated and hence efficient sources of energy as the key. From his perspective, the energy required to perform work was crucial at the onset of human evolution. This energy was dependent on an adequate food intake, which varied in caloric content, to ensure there was enough energy available for both thinking and physical tasks.

Now, scientists from China in a new study published in the journal,,Neuron” prove that energy exchange within the hypothalamus in mice, the brain’s structure controlling a vast number of chemical and biological processes occurring in the body, including emotions, can be responsible for inducing pain and illness. That happens when neurons aggregate in the hypothalamus (circuits) dedicated to energy expenditure, in response to excessive/insufficient food intake, are inadequately firing, causing metabolic disorders or potentially some genetically susceptible psychiatric disorders, according to a Danish scientists’ study also recently published in ,,Neuron”. At the same time, suppression of other types of neurons underlines light-induced metabolic disorders. 

How is this possible? By tracking the development of neural cell shape, structure, and their primary and current functions, we can identify both similarities and differences. However, since the emergence of these structures around 500 to 600 million years ago, notably in jellyfish and ctenophores, the overall configuration has remained relatively consistent. Simplifying, “consistency” enables efficient communication through signal and molecule transmission within an organism’s body. This communication flows through dedicated pathways and molecules, which condition the organism’s functioning and its ability to sustain life or contribute to others. When the signaling transmission through specific circuits or connections in the newly established brain structure, from an evolutionary perspective, is disrupted, problems arise. 

The China’s scientists analyzed neuronal subtypes in the hypothalamus and their selected molecular classification. Some populations of these cells (neurons) can be older, some younger (hence they may have a slightly different shape or structure as such). However, according to scientists, there can be suggested the existence of the evolutionary conservation of some types across species.

What is more, the evolution left traces in the shape of ,,a conserved cytosolic protein for binding retinoic acid with high affinity” in the studied populations of neurons. This subtype of neurons has been identified as an indicator of retinoic acid signaling. There are various signaling pathways in the brain and among specialized neuron populations that regulate hormonal circulation, either triggering or inhibiting actions in the body. However, scientists in a study titled “Identification of a Neural Basis for Energy Expenditure in the Mouse Arcuate Hypothalamus” demonstrated that more primitive cells, mainly located in the hypothalamus, control energy expenditure through neural circuitry.

The striking thing is that the neuronal subtypes ( the molecularly defined neuronal diversity) conditioning energy flows may be associated with metabolic and pain-inducing/silencing path functions. However, as scientists admit, some populations of neurons active in the regulatory processes occurring within the hypothalamus have not been defined, yet. Nevertheless, according to scientists, research over recent decades has established the hypothalamus, particularly the arcuate nucleus (ARC), as a central hub for homeostatic control of energy balance.

• This involves inspecting the major functional response types (e.g., glutamatergic and GABAergic), followed by iterative refinement among main neuronal subtypes to achieve the finest resolution along the hierarchy of transcriptional similarity. In the ARC, it is well-known that glutamatergic neuron activation rapidly regulates satiety, while chronic activation of GABAergic neurons induces food intake and causes obesity, say Ting Wang, Shuping Han, Yaxin Wang, Hui Gong, Peng Cao, Qing-Feng Wu. 

In line with the study, the knowledge of the paths and functions may enable therapeutic measures when needed. Although, in line with previous studies, positive emotions can also be a cure. In response to the request of evolutionandsecurity.com, whether an increased energy expenditure could be in favor of drug cessation in the case of those administrated due to mechanisms triggering a virtual/subjective pain or addiction feeling in the brain, the scientists explain that,, increased energy expenditure, such as exercise, serves as a core component of non-pharmacological management for chronic pain conditions such as fibromyalgia and low back pain.”

Additionally, in line with the scientists’ response: ,,regular physical activity has been proven to effectively reduce pain intensity and improve physical function. As an adjunctive treatment, exercise has been applied in the cessation of nicotine, alcohol, stimulant, and even opioid dependencies. Studies have found that individuals with addiction who engage in regular exercise exhibit higher rates of successful abstinence, lower relapse rates, and greater psychological stability. We are still not sure whether Crabp1 neurons ( the subtype of neurons that are activated by cold and exercise but inhibited by long photoperiod and promote energy expenditure) could target the brain region involved in pain sensing and addiction. If possible, we could also manipulate the activity of this neuronal subtype to ameliorate pain and addiction, say scientists.