Is modern medicine causing a decline in human genetic fitness?

[JPC]

hey
i was wondering

before, those who were the most adapted survived, which made us evolve

but now, even those who have genetical problems , get cured by medecine (like lung replacement for example), but their sexual cells stay the same, and that malfunction in the DNA has chances to be found back in the children of that person

so for a lot of mutations that make us weaker we will survive and send those malfunctions to the next generation

so are we slowly going to become weaker ?

 

[jim mcnamara]

Doesn't work that way. A lot of "defects" are as much environmental as anything else. Meaning it may not be passed on to future generations.

The Main Human Adaptive Strategy: cultural evolution. We are getting better at many things collectively, like the medical assistances you mention.

You need to realize that you are assigning your values to something - ie., "weak" lungs today are bad for humans in the future. Evolutionary change is random - it does NOT have a "good" or a "bad" associated with it. Individuals that make more individuals are successful in an evolutionary sense. So helping kids with bad lungs to survive has an evolutionary "success" outcome. ...If you have to assign values.

 

[Nexus555]

"The Main Human Adaptive Strategy: cultural evolution. We are getting better at many things collectively, like the medical assistances you mention."

I disagree here. Evolution has shown us if you need something for survival, evolution will try it's best to provide it. (Sonars for blind bats, fins for fish, wings for birds, camoflauge insects/animals, etc.) When we use medicines to cure things for us, instead of our natural immune system, we are most likely (though nothing is 100% certain) making our natural selves weaker. The more medicines you take to fix things, the less your body does. Let's say theoretically in the future, 90% of all illnesses, infections and virus infections are cured. We would probably end up developing into an organism with relatively few, if any, disease fighting agents. And if something happened like a natural catastrophe and the medicine supply was destroyed or the knowledge lost, we'd most likely go extinct because we couldn't fight off any diseases with our natural selves.

 

[jim mcnamara]

Evolution does not "try its best" for anything, it has no sense of direction or purpose. It is not a sentient thing.

Most of the adpatations that humans have gotten in the past 500 years are due to cultural change - not evolutionary change.

Here is an example discussing evolutionary psychology - which deals with cultural human changes - a sort of cultural Darwinism I guess.

http://www.psych.ucsb.edu/research/cep/primer.html

 

[JPC]

Yes , its true we get more and more intelligent and we adapt our environment to ourselves, rather than adapting ourselves to our environment

and i agree with Nexus555,
except for : i don't agree it will lead to our extinction, because i think latter we will be able to understand very well DNA, and be able to modify our DNA to survive if any undersired mutations

Thus, if we latter manage to convert our biological system to a , how do u say it in english , maybe : "4 helix" one, to resist better mutations

 

[Nexus555]

It depends how the civilization is in the hypothetical "future" that I stated. It would depend on how the humans would store information and if that information was erased, it would be disastorous.

Also, evolution does somewhat have a "direction." It adapts nearly all aspects of any given organism depending on it's environment. If you live in the ocean, your skin can withstand water for the duration of your life, while land animals if in the water long enough will damage your skin. If an organism lives in extreme cold or extreme hot, the organism is adapted to where it can efficiently survive it's entire life relative to the temperature it's adapted to. Bats live in caves (no light) therefore their optical part of their brain is never stimulated. At first you'd think they'd die off but what happens? They evolve to have sonar sensory and can survive without eyesight.

The same applies to infections. Why are some animals immune to certain diseases while others aren't? Most likely they've had more exposure and over a greator time and have developed a natural resistant to what infections are common for their species. Humans aren't born magically with immunities to some diseases that are life threatening to other animals, and weakness to other diseases. We've gained certain resistances to certain infections through evolution. Now if 90% of all infections had a cure, we'd most definitely use our immune system less, since our immune system doesn't need to work, only on occasion for the other 10% of those uncurable by technology. If kept not using our immune system, let's say for a few million years, do you really think that the race as whole will still have the same immune system from before? This is very doubtful, because the use of the immune system has become obsolete and isn't used enough.

This applies to certain unused organs in our body. We don't need them anymore so they don't work anymore. They are obsolete. So apparently in funny ways, nature does has a plan... a plan for survival and adaptation.

EDIT: Also I'd like to declare a bit of criticism when you said "Evolution does not "try its best" for anything, it has no sense of direction or purpose. It is not a sentient thing."

You say this with sheer certainty that evolution is 100% factual. While I've researched evolution (many times), and agree overall that it's highly probably, nothing is absolute fact as of now. Believing with 100%, absolute certainty that any scientific theory is completely factual is actually ignorance and is avoided in science. No one can say for complete certainty that evolution is 100% true (could be, or could partially be, or could not be at all), current laws of physics (what if physics is a local thing and is different somewhere else? are we missing a lot of information since we're here on this earth, and the universe is supposedly over 13 billion light years across?), etc. Granted, for our local environment, our current knowledge of physics works, and evolution seems almost obvious. But I would suggest avoiding complete certainty on anything scientific, because most of the time things can change and new theories can arise. Our current species is only documented into the tens to hundreds of thousands of years old. Compared to some species or the age of the earth, we are still a very feeble, ignorant and learning species who hasn't mastered the universe yet. Cheers.

 

[paralith]

I think, Nexus, that you may be a little muddled in your understanding of the immune system. When a person's immune system is "used," it is being exposed to an environmental pathogen, and developing antibodies for it. You are not born with antibodies; you have the ability to make them, but their form is not determined until an actual pathogen is introduced. Therefore, any "use" of your immune system during your lifetime induces changes in it that are not heritable. Whether or not we use our immune systems will not effect our children's immune systems, except perhaps in the case of mothers passing antibodies to their infants in utero. Even then, the effect is not genetic.

A better example would be people with weak eyesight. In a species without technology, animals so nearsighted that they can't see things more than six inches away from their faces (like me) would die quickly before spreading their genes for nearsightedness. But in modern humans, people like me can easily survive and bear many children just as nearsighted as I am. But as long as we live in an environment, even if it is a man-made one, where nearsighted people can live just fine, then our species faces no significant risk of extinction.

Also, just because there will be more nearsighted people, doesn't mean the people with good eyesight will reproduce any less. The good genes will still stick around. So should some apocolypse occur that would render nearsighted people doomed, those with 20/20 vision will still be around to perpetuate the species.

 

[Nexus555]

Please then explain how some animals can fight certain infections and diseases while others cannot? If your statement of "You are not born with antibodies; you have the ability to make them, but their form is not determined until an actual pathogen is introduced" is completely true, then why are immune to certain things? If this is true, each time a pathogen tries to overtake us, the outcome of our immune system's ability to fight it would be random, and we would have a higher chance from naturally dieing from any type of bacteria, virus, etc. Immune system primarly makes up of your white blood cells, and assuming they are "cells" I would beg that they are entangled with our DNA and fall under the same evolutionary processes that every other aspect about us does.

 

[paralith]

Immunity is complex, and I'm sure I have understated it to some degree, I will give you that. But the main reason why we are "immune" to some diseases that effect animals and vice versa is this: a given type of virus has a specific host or range of hosts that they attack. They are adapted to attach to and enter certain types of cells, and will essentially "ignore" others. Some viruses have greater ranges than others, and multiple species may be vulnerable. The same goes for micoorganism parasites. They are adpated to specific hosts. Take malaria, for example. Mosquitoes carry it, but suffer no ill effects. It's not until the Plasmodium gets into a human that they begin to multiply and cause harm. Big problems can arise when a virus specific to one species appears to have adapted to be able to target humans - like avian flu.

 

[BoomBoom]

You say this with sheer certainty that evolution is 100% factual.

Do you have an alternative "better" explanation?


Immune systems (adaptive) undergo their own "evolution". This adaptive nature allows them to identify pathogens (which also evolve) and build a response specific to that pathogen. Of course this is overly simplistic since there are many aspects of the immune system(s) as well as many aspects to different types of pathogens. But, keep in mind that the vast majority of these "cures" you mention are vaccines. This is not a "cure", but just a presentation to your immune system to recognize the pathogen and have the ability to mount a full-blown response from "memory" should this pathogen ever introduce itself again. If you are not vaccinated, you have no "evolved" immunity to that disease.

 

[JPC]

anyways even if our imune system is getting weaker or not
it would be easy to store some DNA from people of today as a backup

 

[Moridin]

Also, it is important to separate the notion of antibodies from the cells producing antibodies. Antibodies certainly is not determined until an actual pathogen is introduced, while the cells producing antibodies are.

Evolution does not have a direction. It is completely blind and it is certainly not progress. Take bacteria for example. Strain A can be more successful than strain B in a certain situations. Strain B can be more successful than strain C in other situations. Finally, strain C can be more successful than strain A in yet another environment. The environment is constantly changing.

Complex traits are rarely decided by just one gene; rather it is a combination of several genes at different loci, both recessive and dominant can be involved as well as environmental factors.

 

[picklefeet]

Please then explain how some animals can fight certain infections and diseases while others cannot? If your statement of "You are not born with antibodies; you have the ability to make them, but their form is not determined until an actual pathogen is introduced" is completely true, then why are immune to certain things?

I feel that the ability to produce antibodies is based on the recognition of the disease. In early Europe, small pox, chicken pox, measles, etc. were completely survivable because of the inherited resistance to a common disease. But when the Europeans came to the Americas, the natives immune systems didn't understand the disease and couldn't fight it off. But because of how common these diseases are, people of North and South American descent are able to survive such diseases. I am not talking about small pox in the previous section, because that is dangerous for people even if they are of complete European descent, such as myself.

 

[Moonbear]

Medical intervention will likely result in the same effect that agriculture has had on farm animals. In farm animals, the term relaxation of natural selection is used to refer to the protected environment they are maintained in. Traits that would have been selected against in their wild counterparts are no longer selected against (and instead, breeding programs select different traits desirable for meat or milk production). What happens is you get more variation in traits that will make many of the members of the population unfit for survival in the "wild." For example, among dairy cattle, there is a very wide range of maternal ability/care. Some dairy cows still are great mothers to their calves, and others are terrible mothers. This is no longer an important trait, because the calves born to bad mothers are bottle-fed and raised by the dairy farmer, not the cow, and still survive. So, yes, it would not be surprising for the prevalence of certain diseases to increase in the population if medicine can prevent them from having any impact on reproduction and passing those traits on to future generations. However, that doesn't mean humans will be "weaker" since those traits have been rendered unimportant by supplementation of medical care. Also, many of the "diseases" being treated would not have impacted reproductive ability anyway as they occur later in life. Or, in the case of assisted reproductive technologies, are often needed not because of a genetic problem, but either because the parents are attempting to achieve pregnancy at an older age when it is normal for fertility to decline, or due to things that happened to them as they got older...scar tissue in the reproductive tract from an infection, infertility as a consequence of treatment for something else, etc. Patients seeking assistance with reproducing are not necessarily infertile, but subfertile. With more time, they may have gotten pregnant the natural way anyway. In the case of those who are infertile, the offspring are not actually their biological offspring, but gametes from other fertile people are combined with those of the fertile parent, so that the parent with infertility is actually not contributing to the genetics of the offspring.