It seems logical that evolution and natural selection get rid of everything unnecessary, much less harmful. But then it is unclear why our ancestors passed on the tendency to depression to us, instead of giving it up back in mammoth times.
Scientists are also concerned with this question. Biologists, psychologists, and anthropologists have developed several hypotheses to explain depression as a function of evolution. Perhaps the symptoms of the disease helped humans adapt and survive. Let’s try to figure it out.
How scientists explain depression in terms of evolution
So far, these are all just theories, and not necessarily compatible with each other. And some researchers do not consider depression to be an adaptation method at all.
1. It helps to stop useless and dangerous actions
Some scientists suggest that strong negative emotions, including those caused by depression, sometimes increased our ancestors’ chances of survival. For example, frustration or discouragement may have caused a person to abandon activities that were too dangerous or time-consuming and had a low chance of success.
For example, even the most skilled hunter understood that going after a large animal alone was dangerous, and refused the venture if his fellows did not support the idea. No matter how much a man would like to get a lot of meat or a beautiful skin, he realized that life is worth more. Otherwise, it was very likely to die.
Presumably, depression caused apathy and so increased human survival rates. And therefore overcame natural selection.
It is quite possible that this mechanism sometimes works unconsciously. For example, psychologists have long noticed that infants, left without their mother for a long time, stop crying and shrink into a ball with their hands around their knees.
In the past, it could save a baby’s life. After all, while the mother is not around, there is no one to protect the baby from predators, and therefore it is better for the baby to lay low. In addition, less energy and nutrients are consumed this way. Such behavior could be preserved as an unconscious reaction to dangerous conditions, when any action only worsens the situation.
2. Depression “helps” in relationships with others
In primitive society, expulsion of a man from his tribe meant an agonizing death. Why? Because one cannot hunt or defend oneself against enemies or predators.
According to some scholars, depression was necessary to avoid conflict. Low self-esteem and depression forced a person to give in and accept the opinions of others. As a result, the likelihood of remaining in the tribe increased.
This mechanism was especially pronounced when people found themselves at the bottom of the existing social hierarchy. A depressed state of mind helped to reconcile with the status quo and not to take actions that could cause discontent with the others and lead to expulsion and death.
A similar thing can be observed in the wild. For example, a male leader chimpanzee, defeated by a stronger rival, is forced to accept his new status and become submissive and quiet. After that, the animal has a state similar to depression. Passive behavior as if allows the former leader to protect himself from further attacks. This means to preserve life and the possibility to pass on the genes to the offspring.
Roughly the same thing happened to people in primitive society. Former leaders gave way to new leaders, but they survived because they offered no resistance after defeat.
3. Depression is a way to get support
Other scholars suggest that depression is an extreme version of a cry for help, a way of signaling trouble.
In primitive society, people would not have survived without the support of others. Especially in a difficult situation, which is exactly what can trigger the development of depression.
Thus, a man who is unable to hunt needs help. For him, an attempt of suicide or a silent refusal to fight do not constitute a great threat – he will not survive on his own in any case. But in this way, the person can attract the attention of others and receive the necessary support.
Postpartum depression, when the mother does not receive the necessary help from the child’s father and relatives, works in about the same way. This reaction becomes an adaptation strategy, a way to create offspring and prolong her lineage.
4. Depression helps solve difficult problems
Depressed people tend to think about the same events or things all the time. Most doctors believe that such thinking is destructive because it takes away a person’s full attention and prevents him or her from doing anything else.
However, two American scientists, Paul Andrews and Anderson Thomson, Jr. They suggested that in some cases such fixation and concentrated reflection are necessary. It is as if the body forces a person to concentrate on a difficult problem. A depressed person does not want to have fun or socialize, which means that all his energy and time are spent on solving the key issue.
That is, depression turns out to be a way of adapting to difficult situations and hypothetically helps to overcome them.
This assumption is supplemented by the fact that people in a depressed mood make more reasonable decisions than their joyful opponents. The former, as a rule, more often doubt and try to avoid unnecessary risks. The latter act decisively and less often think about the consequences.
This is exactly how the participants in the experiment on the effect of mood on decision-making behaved. Investors who praised their investments began to act recklessly and make mistakes. But people who were criticized acted more conservatively and make money.
5. Depression helps fight infections
In 2012, American psychiatrists analyzed many genomic studies of people with depression. Scientists noticed that genes that are associated with an increased risk of developing this psychological illness are also linked to the body’s effective immune response to infections.
That is, depressive alleles (different forms of the gene) are simultaneously immunological alleles that are responsible for protecting the body from pathologies. In this case, the propensity for depression becomes advantageous from the evolutionary point of view: it was various infections that most actively killed the ancestors of modern humans.
Tellingly, “depressed” genes are more often found in people who inhabit regions with a higher risk of infection.
For example, some residents of Ghana get their water from clean wells, while others get it from polluted rivers. Naturally, representatives of the second group die of infections more often. This is why their bodies adjust to natural conditions: river dwellers develop the very “depressive” genes that protect them from infections.
That is why, perhaps, depression was preserved in the process of evolution as a genetic response to diseases rather than as a way of social adaptation.
Does this mean that depression is useful?
No. Maybe evolution really did have its own reasons for preserving depression – scientists have not yet given an exact answer. However, such a condition cannot be considered normal or even more useful.
Depression is a dangerous mental disorder that must be treated. Even if it was once beneficial, this does not mean that it is worth ignoring today.