Is intelligence inevitable in evolution?

Knowledge : Evolution of mind

People have always felt mentally and intellectually superior to animals. The list of supposedly “unique” human abilities such as consciousness, toolmaking, morality, self-reflection, religiosity and language is long. However, in the past 20 years, behavioral researchers, psychologists and neurobiologists have presented research results that increasingly question this uniqueness. There is now no human intellectual and intellectual ability that researchers have not found precursors to in the animal kingdom, even in distantly related animal groups such as octopuses, corvids and dolphins. There seems to have been an evolutionary continuum of the mind, as put forward by Charles Darwin in his late work “The Descent of Man” in 1871, and not a “fulguration,” a lightning bolt of the mind, at some point in the development from ape to man, like for example Konrad Lorenz and Karl Popper thought and many philosophers still do today.

Nervous systems and brains are a product of evolution. If - as neuroscientists have shown - intellectual and intellectual performance are inevitably linked to brain processes, then there should be a co-evolution of brains and intellectual performance. Both would have to be subject to the known principles of evolution, with the result that the “better adapted” prevails. But if you try to reconstruct this process of co-evolution of brain and mind more precisely and to fathom its mechanisms, you quickly come across facts that seem to be incompatible with the conventional picture of evolution and at the same time shed new light on them Cast nature of the human mind.

The first insight is that you don't need a nervous system or brain to be successful. The most numerous and successful living beings on our earth, the unicellular organisms, do not have a nervous system. Most animal phyla have only a very simple nervous system, consisting of a throat ring and nerve cords extending from it, which are connected to sensory organs, intestines, glands and muscles - and they have survived with it for 600 million years. Surprisingly few of them, mostly predatory species, have more complex sensory organs and, at the same time, have developed a moderately complex brain from the pharynx. Significantly more species, on the other hand, have simplified their moderately complex nervous system and brain again, mostly in connection with a sedentary or parasitic way of life, and the vast majority of species have remained as they came into being for hundreds of millions of years. Evolution is by no means identical with “higher development” - on the contrary.

Complex brains and intelligent behavior are the exception in evolution and are only found in invertebrates in cuttlefish such as the octopus and arthropods, and especially in insects such as the honeybee. Vertebrates (cartilaginous and bony fish, amphibians, reptiles, birds and mammals) usually have complex brains, but even here only a few animal groups have high intelligence such as corvids, parrots, elephants, dolphins and monkeys. These animals have considerable memory and intellectual abilities, they make tools, they can recognize themselves in the mirror, they are conscious and have a complicated communication system made up of sounds and gestures. Humans, belonging to the primates, tower above these animals only quantitatively, not qualitatively.

The second insight is that such “high achievements” developed independently from less intelligent ancestors in many cases during evolution - after all, squids, insects, birds and mammals are only very distantly related to one another. Forms of high intelligence almost always appeared when animals entered new habitats in which higher sensory performance, better neuronal information processing and flexible, innovative behavior were required. The basic principle of this process is not, as it is called in many biology textbooks, to win the competition for resources in the previous habitat, but to avoid competition. For example, some great apes tried to escape the competition that was prevalent in the shrinking jungle by dodging into the savannahs. This explains why the great apes “who stayed at home” successfully continued to exist in the jungle and why the two groups (until recently) did not interfere with each other. It wasn't until a million years later that humans developed a greatly enlarged brain, tool making, fire use and complex language.

If you now look at the brains of animals, which are characterized by high cognitive performance, another problem arises. The smallest of them, like that of a honey bee, weigh only a few milligrams. Despite the high intelligence of these animals, the brain of a magpie weighs only around 10 grams, while a rhesus monkey, which does not appear much more intelligent than a magpie, has a brain of around 90 grams. Very large brains can be found in elephants weighing up to 6 kilograms and whales up to 10, but neither species is characterized by outstanding intelligence. With an average weight of 1.4 kilograms, the human brain is significantly smaller than that of elephants or whales. Brain size does not seem to have anything to do with intelligence; animals with smaller brains can be more intelligent than those with larger brains.

The same applies to the number of nerve cells in the regions of the brain that are directly related to cognitive performance. The fungal bodies in the honeybee's brain contain just 300,000 neurons, the vertical lobe in the octopus' brain contains at least 25 million, the mesonidopallium in birds an estimated 200 million, the cerebral cortex of a macaque monkey around 400 million, and that of an elephant and a large whale around 11 billion and finally the human cerebral cortex 12 to 15 billion. The number of nerve cells involved in intelligence can therefore vary by a factor of twenty in similarly intelligent animals such as corvids, macaques and elephants. It only seems to “fit” with humans: they have the most nerve cells in their cerebral cortex and are the most intelligent!

But what then matters, if not the size of the brain or the number of cells? A detailed analysis shows that animal and human intelligence depend on two factors: the processing speed of information and the storage capacity of the nerve networks. The first factor in turn depends on the mean distance between the nerve cells and the speed at which the nerve fibers are transmitted: the closer the nerve cells are packed and the faster the speed at which they are transmitted, the faster the information can be processed. The storage capacity, on the other hand, depends on the number of neurons in the memory network and the contact points between them, the synapses: the more neurons and synapses, the larger the memory.

If, like the honey bee, very small neurons are very tightly packed, then these brains can have a high processing speed with medium memory capacities. That explains, at least in part, their amazing intelligence. Elephants and whales have very many neurons in their huge cerebral cortex, which is beneficial for memory formation, but the packing density is low, the nerve fibers are long and their conduction speed is low. This explains why elephants and whales, despite their giant brains, are nowhere near as smart as macaque monkeys, with a tenth of the brain mass and cell count. Although humans have a significantly smaller brain than elephants, they have smaller cells, a higher packing density and a high transmission speed. So while processing speed is the trump card for small animals and brains and memory is the trump card for very large animals and brains, the human brain optimizes both, and this is an essential reason for its outstanding intelligence.

We thus recognize two things: Firstly, within evolution, spirit and intelligence often emerged independently of one another. In humans, a number of factors come together that greatly increase the efficiency of their brains, in particular the evolution of a syntactic-grammatical language around 100,000 years ago, which can be viewed as an extreme intelligence amplifier. Second, there is apparently a kind of basic structure of mind and intelligence that has often been realized independently of one another during the evolution of animals, mostly in connection with the conquest of new habitats. This basic structure has developed further in humans than in other animals, but the human mind and human intelligence remain within the framework of scientific understanding and are not a metaphysical event. The more precisely we understand this basic structure, the sooner we could one day recreate it in principle as artificial intelligence. But it can be that the sheer complexity and the necessary materials throw a thick line on us.

Gerhard Roth is a brain researcher and professor of behavioral physiology at the University of Bremen. A detailed presentation of his theses can be found in the book “How Unique is Man? The long evolution of the brains and the mind ”(Spektrum Akademischer Verlag, Heidelberg 2010. 442 pages, 24.95 euros).

There are numerous examples of intelligent behavior in nature. Apparently the spirit arose gradually and did not suddenly appear in primitive man.

Complex nervous systems and brains have arisen independently several times. This usually happened when animals penetrated new habitats and had to master new challenges there.

Most living things can do without a complex brain. Einzeller are extremely successful and have no nervous system. In fact, more animal species have simplified their complex nervous system again than vice versa.

Apparently, neither the size of a brain nor the number of nerve cells alone determines the intelligence of an animal.

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