Warm-bloodedness turns out to be one of the main differences between birds and mammals and other animals. Maintaining a stable body temperature requires a significant increase in metabolism, but it also changes the body's physiology and behavior. Read more about the effects of constant body temperature in the Rambler article.
What is warm-blooded?
Warm blood (endoexia) is the ability to maintain a constant internal body temperature regardless of environmental temperature. In birds, this temperature reaches about 40 °C, in mammals the average temperature is about 37 °C, significantly higher than that in most habitats. Maintaining this temperature requires a lot of energy: the body must consume more food than a thermoregulatory (cold-blooded) animal.
That's why warm blood is such a rare phenomenon: it developed independently in two evolutionary lines – in the ancestors of birds (theropod dinosaurs) and in the ancestors of mammals (cynodonts) about 200 million years ago, during a period of significant climate fluctuations. This convergent evolutionary response to environmental instability points to the significant advantages that warm-bloodedness confers.
Why is it expensive to keep warm?
Maintaining a constant temperature is an energy-intensive strategy. For example, for an animal the same size as a boa constrictor, the warm-blooded creature must eat about 30 to 50 times more to maintain a constant core temperature above air temperature. These increased costs can make warmblood breeding unprofitable without several key advantages.
One of them is that biochemical processes in the body are more efficient. At high temperatures, the rate of biochemical reactions increases, which reduces the relative energy costs of nerve impulse transmission, improves muscle function and allows you to maintain vigorous metabolic processes. This, in turn, allows warm-blooded animals to operate over a wide temperature range without dependence on solar regimes or surface temperatures.
Another important advantage is protection against infections. Many pathogenic fungi and bacteria cannot survive at temperatures above 37°C. This means that warm-blooded animals are less susceptible to many types of infections that affect reptiles, amphibians and invertebrates.
Freedom of movement: why are warm-blooded animals more active?
In cold-blooded creatures, activity depends directly on the environmental temperature: when the air is cold, muscles and nerves slow down, the animal becomes lethargic or completely immobile. For warm-blooded animals, this limitation disappears: they do not have to wait for the “right” time of day or season. They can hunt, feed and move regardless of outside temperature conditions.
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This provides significant ecological advantages: warm-blooded animals can occupy more geographical niches, tolerate temperature fluctuations, avoid seasonal resource shortages, and are active at dusk, at night, or in cold weather when many cold-blooded predators are less likely to be active.
It was this expansion of behavior – the ability to act and survive in a variety of conditions – that became the basis for the development of complex patterns of interaction with the world: from social strategies to spatial exploration, indirectly influencing the evolution of the brain.
How does body temperature affect brain function?
Warm blood not only affects the body, but also the brain – its speed of activity and network organization. The efficiency of neural processes depends greatly on temperature: as temperature increases, the speed of nerve impulses increases and the refractory period – the time needed for neurons to become active again – decreases.
When switching from a cold blood brain temperature of about 15°C to a warm blood brain temperature of about 37°C, the speed of neural circuits more than doubles and neurons can operate faster and more accurately. This accelerated neural network dynamics paved the way for the formation of more complex feedback connections between neurons—the basis for the integration of complex sensory, predictive, and behavioral information. This leads to two important changes that may contribute to the development of “conscious” neural circuits:
- Increases the speed of nerve signal transmission, helping to reduce time delay between brain areas.
- Reduces the neuron refractory period, allowing for denser and more stable feedback loops.
These changes make it possible for the brain not only to respond quickly to external stimuli, but also to maintain internal models of the world, repeating and integrating information at a higher level.
How did warm blood change animal behavior?
What exactly separates consciousness from a complex reflex? Modern neuroscientific theories tend to view consciousness as complex, self-referential information processing, in which the system does not simply respond to stimuli but also generates and operates on internal representations. And here, warm blood may play an important role, giving the brain the engineering ability to support such circuits.
A constant high body temperature not only ensures biochemical stability, but also reduces the dependence of neural activity on external thermal noise, maintaining network function under wide conditions. This means that the neural circuits responsible for sensory integration, memory and prediction can grow faster and stronger in cold-blooded creatures.
This physiological “stepping stone” provided the opportunity to develop more complex forms of behavior that we would later call cognitive abilities. These include planning, social interaction, predicting the future, and learning from experience.
Warm blood is an evolutionary advantage
The transition to warm-blooded animals ushered in not only physical but also behavioral autonomy for the ancestors of birds and mammals. In contrast to reptiles and amphibians, whose activity is limited by environmental temperature, warm-blooded animals can use their body as a more stable system, less dependent on the outside world.
Philosophically, this can be considered a transition to internal autonomy – the basic condition for developing a complex perception of the world and one's own “I”. The less your reactions are dictated by external conditions, the more self-sufficient your internal processes become: wanting, choosing, remembering, planning.
This does not mean that warm-bloodedness itself gave rise to consciousness, but it greatly expanded the biological pool from which it could arise. This explains why birds and mammals have risen to the top of ecological niches and why their behavior, social structure, and learning abilities exceed those of most cold-blooded animals.
We previously wrote, How terrifyingly the brain distorts reality.
