This is a highly speculative yet interesting topic: I read about some diseases that possibly could have an advantage under certain conditions
-sickle cell disease (potentially protecting against malaria)
-diabetes type 2 (might have an advantage in creating heat in cold climates , i.e. ice-age)
-obesity (starvation)
-schizophrenia (creative personality, could be useful for the tribe in some instances, speculative I admit)
are there any other diseases, which spread could be explained with evolution/natural selection?
Schizophrenics really are not particularly creative. No doubt there have been few schizophrenics who have done creative things, but probably a lesser proportion than in the general population. Creativity generally depends on the ability to think clearly, which schizophrenia takes away. It is really a very disabling condition.
You seem to be asking if ‘genetic’ conditions which have ‘obvious’ detrimental effects can have a less ‘obvious’ benefit. One answer is that all of them do if they survive over time. That’s how beneficial effects are defined in evolution. But modern humans present a unique situation. The great diversity of genetic structures in humans, large population, lack of isolation, altruism, and ability to compensate for genetic disadvantages make it very difficult to resolve these questions.
Malaria is a case where there is substantial evidence that genetic resistance to malaria is an evolutionary adaptation. But in the case of sickle-cell anemia and some forms of thallasemia there are still questions about how a fatal genetic combination propogates. The correlation with malaria is clear though. But malaria seems to have arisen only 50,000 years ago, which is a short time on an evolutionary scale. Given enough time, sickle cell anemia may not survive. The explanations get more compicated the deeper you dig. Genetic study indicates that the genes responsible for sickle cell have developed independently in humans over time. That is an indication of an underlying genetic structure conducive to the development of sickle cell genes. At that point the complexity of genetics makes it currently impossible to determine if the underlying structure could disappear over time. It seems more likely that a malaria vaccine or eradication will change the evolutionary conditions.
The other cases you cite are more controversial, and usually approached from the typical fallacious concept that evolution has a purpose. Genetic predisposition to the poorly defined condition called ‘obesity’ may have nothing to do with starvation, and more to do with modern agriculture. I haven’t heard of the diabetes theory, but it sounds like nonsense. The detrimental effects of diabetes type 2 are strongly tied to environmental factors, especially that poorly defined obesity, which may not have been prevalent in the ice age.
So basically you are left with genetic disorders that don’t prevent reproduction, but still seem to have detrimental effects. But from an evolutionary standpoint, reproduction is the only benefit, and anything that inhibits reproduction the only detriment.
I’m sure others will join in the speculation you seem to be seeking. But IMHO you will develop more understanding from studying the dynamics of evolution.
To clarify about obesity, some populations are more efficient at storing fat. When food is scare, this provides an advantage. When technology brings things like deep fried twinkies, then they get fat.
Although some schizophrenics are creative (Paul Gösch, Wesley Willis), for the most part the severe ones have difficulty committing to such pursuits. Possibly related though: many bipolar people are resistant to treatment because they feel extreme creative during the manic phase, and medication flattens their affect. I don’t know of any evolutionary links, though.
It bears saying that some diseases continue to exist because they don’t confer a disadvantage, but also don’t have an advantage. Huntington’s disease appears after most people have already had their children, thus the negative effects don’t harm their chances of breeding (but might affect child rearing).
Studies have been done by on the
potential benefit of ADHD like traits in nomad cultures
[QUOTE]
Increased impulsivity, ADHD-like traits, novelty-seeking like traits, aggression, violence and/or activity levels may help nomads obtain food resources, or exhibit a degree of behavioral unpredictability that is protective against interpersonal violence or robberies. /QUOTE]
The majority of migraine sufferers have some increased sensitivities that could improve chances of survival.
These increased sensitivities originate in the brain, not in the nose or eyes, ect.
Increased sense of smell. Especially noxious odors. Smoke. Fumes. Usually a person with migraine will become aware of dangerous odors before a person who does not get migraines. A home gas leak would be an example. Two sleeping people during a house fire, the migraine person has a better chance of waking up in time to escape.
Increased light sensitivity. Especially strobe- like lights often associated with emergency vehicles.
Increased movement sensitivity. Car sickness is a very common migraine associated phenomenon. This could mean survival under circumstances where early detection of motion abnormality signals something is amiss in a vehicle.
Increased noise sensitivity. Changes in noise are picked up earlier by a person who gets migraine. Non- migraine people can easily ignore sounds that a person with migraine pays attention to, whether they want to, or not.
Taste abnormalities of migraine in theory could prevent eating bad/tainted foods.
A person who has migraines is effectively the canary in the coal mine.
Only they don’t drop dead when there is a problem, they get a headache.
And sometimes that can mean literally sensing danger before anyone else.
The evolutionary benefit is this.
Migraine itself does not cause death ( only misery).
Migraine sensitivities have potential to warn when here might be something dangerous, and even life threatening.
Do you mean the disease itself is beneficial or that beneficial biological changes, when taken to extremes, can cause disease?
Some degree of mutation in red blood cells makes you resistant to malaria. Too much gives you sickle cell anemia.
A degree of insulin resistance and stored bodyfat helps you survive in famines. Too much causes obesity & type II diabetes.
Type I diabetes may be a response to survive in winter climates like Scandinavia.
But there is no real benefit to sickle cell anemia, type II diabetes or obesity. However the biological changes that predispose a person to them did help some people in some parts of the world.
Supposedly trying to figure out why depression is so common is something evolutionary psychologists want to work on. Other mental illnesses like schizophrenia or bipolar only affect 1-2% of the population. Depression affects 10-20%. So people aren’t sure why depression is so common since it has so many negative effects from an evolutionary POV (lack of motivation, lack of energy, lack of desire to socialize, suicidal or passive suicidal ideation, weakened immune system, less interest in raising your kids, etc) which put you and your family/tribe at higher risk of death.
Some people say that the depression itself offers some advantage. But to me it may just be a side effect of higher cognitive thinking. Knee and back pain are common and happen to huge numbers of people. But they don’t offer any evolutionary benefit, they are just unwanted side effects of standing upright and walking. The reward (mobility) is greater than the price (joint pain). Depression may fit that bill and just be a tolerated side effect of higher cognition and brain development, or it may serve some unknown purpose all on its own. But at the end of the day it is a far more common mental illness than the other mental illnesses and I don’t think anyone knows why yet.
Did you mean to type Type II diabetes may be a response to survive…? Because while I can see II having survival advantages in certain environments (sadly, not mine), it’s hard to imagine for Type I. It was my impression that, historically (i.e., before we knew how to make insulin) that most type-I diabetics died very young.
Just to make it clear, When I mentioned obesity being a potential survival enhancer, I was of course talking about the ability to easily store energy as fat. Not obesity itself which of course most often is a consequence of eating too many mcnuggets
True, but the potential evolutionary advantages favor trichromacy. For every advantage of colorblindness you can find, you can find dozens of disadvantages. However, it is not such a great disadvantage that it disappears from the gene pool.
Type 1 diabetes is more common among people from northern europe and causes a lowering of the freezing point of bodily fluids. The assumption is that during the last ice age it offered an advantage. However I don’t know how people survived into adulthood with it.
There is more than a little evidence that a single dose of the sickle cell gene conveys some resistance to malaria. Maybe the strongest evidence is that the geographical distribution closely tracks that of malaria. A double dose, however, has to be deleterious. Those poor people are paying the evolutionary price (speaking entirely metaphorically, let me hasten to add) for their heterozygous (i.e. single dose) relatives. Luck of the genetic draw.
There is a conjecture, but the evidence is pretty iffy, that a single dose of the Tay-Sacks gene confers some resistance to insulin. A double dose is invariably fatal within the first couple years of life, but again those sufferers are paying, perhaps, the genetic price for whatever protection may accrue to their relatives.
I don’t know of any other situation for which there is more than mere speculation. Type I diabetes was invariably fatal before insulin.
Thanks for the information; I’d seen that, but somehow I thought it was about Type II. Probably because I’m a II my ownself.
As for how they survive into adulthood, I can imagine a reduction in insulin production (as opposed to an outright lack) having the described effect in a population, only to become lethal eventually. As long as the personwith the reduced insulin production can survive to a breeding age, and be able to breed, it can be passed on, after all.
It is an interesting theory no doubt, however it doesn’t cut it completely . DM
type 1 is thought to have an autoimmune pathogenesis , where the Beta cells in the pancreas are destroyed. No beta cells means no insulin production.
In modern day at least you have what is called a honeymoon period where your insulin production slowly drops. Once you develop bona fide Diabetes you do not produce any insulin. No insulin is not compatible with survival.
It would be possible though that the people developing diabetes after puberty could have offspring before they die. This raises other questions of the offsprings survival chances having lost at least one parent.
I think this theory is much more compatible with DM2, and I have a vague memory I have read about it i from credible sources .
Im not well versed in evolution would be very interested indeed if anyone have any more info on this.
“schizophrenic” is a medical diagnosis, one that people get if they lost the ability to think clearly. A “schizophrenic”'s relative who can think clearly might well take advantage of greater inquisitiveness and willingness to take unusual ideas seriously.
An article on norvegian folklore hero Askeladden - Wikipedia who does well while being a bit too eccentric for the tastes of normal people around him makes the following speculative claim:
