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It is assumed, for the purpose of this question, that Charles Darwin, in the 19th Century, formulated the concept of "Survival of the Fittest". Penned in his book "The Origin of the Species", which is internationally renowned, the theory is that each creature alive on Earth today is the way it is because it has evolved, through many millions of years, to be the way it is.

The concept of "Survival of the Fittest" itself is the idea that that evolutionary process occurs because only the creatures most suited to their environment survive. Thus "unfit" offspring will die out over time.

I don't wish to discuss the validity per se of Darwin's Theory of Evolution - for the purpose of this discussion, we assume that it is true. However, I put it to you that, specifically in modern-day developed countries*, so many stringent Health and Safety measures are put into place, and use of medicine and medical practice has reached such a high level of success, that evolution in humans has been artificially halted.

My question is: As a result of human progression in science (specifically medicine), have we created ourselves a plateau in the evolutionary process?

I have reached the age I am without ever having broken a bone in my body (at least not one of the major ones, to my knowledge). What if I discover that my body can't heal broken bones and that I'll die if it happens? But I pass that gene on to my child, who, in turn, is a bit of a womaniser and has seventy offspring, all with this same gene; and so on ad infinitum. This rather extreme example helps to illustrate my question, but the point is that, after a few generations, many hundreds of thousands of people would not be able to withstand a simple earthquake or other natural disaster.

The question title I had originally planned was: "Survival of the Fattest?", but I didn't want to make the already rather controversial question more provocative than was necessary!

*For example: The United States of America, Canada, Western Europe, Australia, New Zealand and many others

7

No, "evolution" has not reached a plateau

It doesn't make sense to conceive of a "plateau" when it comes to evolution by natural selection outside of a situation where a particular species is subject to relatively little evolutionary changes over a long period of time because the environment is relatively stable. Only in that sense does the term "plateau" make sense (and is actually used) in evolutionary biology.

Evolution by natural selection cannot be halted or turned off, slowed down or sped up. Those concepts do not have such properties. Adaptation, on the other hand, can be slowed down or sped up, depending on the speed at which the environment changes as well as the rate of reproduction, and the rate at which mutations which occur. Adaptation is the property of species I think you mean to refer to. What I think you are really getting at is:

Is it possible for a species to adapt in such a way that is not beneficial?

The answer to this is tricky.

  • First, recall that "fitness" is a relative term. Generally speak, organisms are more fit if more of their offspring survive to reproduce than than others. It doesn't really have anything to do with the "fitness level" of the parent organism, i.e. how long they live, how strong they are, etc. It's all about the successful propagation of genetic material.
  • Second, recall that adaptation to an environment is based on an essentially random process: mutation, crossing over, etc, are essentially arbitrary, such that even when an environment changes, it may not always happen that a species has the correct mutations that will benefit it and allow it to survive the new change. More often than not, when relatively radical changes come, the species simply dies; this is call exictinction. You don't hear about it as much so people generally assume most species adapt successfully to their environment, but this is simply not true. It is estimated that 99% of all species that ever lived are extinct.

With these in mind, is it possible for a species to evolve in such a way that their adaptations are not suited for the environment? Absolutely, and this is particularly true in rapidly changing environments. With advances in medicine, we prevent the deaths of millions of people every year who would have otherwise died from some crippling genetic deficiency, and in many cases they grow up and pass on those genes.

The question which remains is whether this is a good or bad thing. I actually wrote a paper on that... Unfortunately, it's really outside the scope of this question, but see Marian Van Court for a start of where I think your reasoning is taking you... (Note that her reasoning is not entirely solid and I definitely don't prescribe to her views)

6

This is really a biology (human genetics) question, not a philosophy question, but I suppose that there is no better fit among the Stack Exchange sites.

I also need to clarify a few of the points of biology.

First, the question is mostly about selection. Although there are random processes that affect biological evolution, only selection turns evolution into an optimization algorithm. Hence, it does make sense to consider what kind of selective pressures exist, and consequently, what is being optimized. Thus, the question is best phrased in terms of selective pressures affecting human evolution.

Second, let's keep in mind what "fitness" actually means with "survival of the fittest". You could be able to run a marathon, bench press 300 lbs, and so on, but if you have no children (and do not aid siblings of yours in a way that allows them to have more children), your fitness is zero. Fitness means only "reproductive fitness", though to be fair it should be considered arbitrarily far into the future (e.g. if you have 20 children none of which will themselves have any children, your fitness should again be considered zero (at that point)).

So what actually matters to fitness? Let's leave aside the more complicated (but important!) case of assisting relatives, and focus just on the individual aspect. The two things that matter are: (1) How many children do you have? and (2) Do those children survive until they're old enough to have children themselves (and, in fact, do they)?

It is likely true that for a good portion of the world's population, physical fitness and reproductive fitness are being decoupled, because we have many technological alternatives to intrinsic strength and robust immune systems (cars, antibiotics, etc.). Also, for a smaller portion of the world's population (i.e. China), the number of children is also approximately fixed.

So for China, the answer to the question "what selective pressures are there" is "essentially none" (except for essential biological processes necessary to even survive until birth). In other industrialized countries, the selective pressures are in favor of people who have large families; most everyone survives, so only the birth rate remains. Much of the "developing" world has not seen a dramatic change in selective pressures, though details of availability of food have changed somewhat.

The consequence of a lack of selection is an increase in the diversity of the gene pool, much of which would have been maladaptive in earlier more stringent selection environments. Genetic defects accumulate slowly, so one doesn't have to worry much about drift until hundreds or thousands of generations have passed (and I would be very surprised if the same conditions persist in e.g. China for that long).

The consequence of selection for large families is more interesting, and could change the gene pool in only a handful of generations. For example, if there were a (dominant) gene that caused those who have it to have a family twice as large as average, after only 10 generations, it would be a thousand-fold overrepresented compared to the small-family variant. Of course, the earth can't tolerate a 1000fold increase in population, so eventually this alelle may become disadvantageous (as everyone in the family suffers to such an extent because of the large size that even though there are more of them, they are less reproductively fit than a smaller family). Still, it doesn't matter why the gene was effective; if it made someone really love children, or gave them a latex and contraceptive allergy, or predisposed them to Mormonism (or another religion that promoted large families), it would have the same impact: that gene would be favored. The question, though, is whether such single genes exist. Because, of course, if it takes many genes to generate a large difference in family size, almost none of the children in that family will actually have all those genes. So the process of "fixation" (i.e. those genes taking over) will be slow. In most cases, although genes do appear to play an important role in many human behaviors, the number of genes is large. Thus it is likely (although here we can only speculate, whereas in the genetic drift case we know) that it will be many generations before this would have much impact either.

(And, of course, don't forget the large fraction of the world's population where the pressures are different.)

So, bottom line is: in some places yes, we're approximately at a plateau but plateaus are not so bad in the short term; in other places no, there are sizable pressures still; and we probably have quite some generations before we'll see major consequences from those pressures.

Eventually we as a species will have to deal with these issues. Presently, however, it is not one of our most pressing concerns. (Let's get resource depletion, overpopulation, global warming, etc., all dealt with first.)

  • (Let's get resource depletion, overpopulation, global warming, etc., all dealt with first.) - Surely these are all problems that stem from the same thing? Overpopulation comes from the low death rate in developed countries, which leads to resource depletion and global warming? – oliver-clare Nov 6 '11 at 10:45
  • @LordScree - We could deplete, overpopulate, and warm the planet with high death rates. Don't mistake technological effectiveness in resource extraction and consumption with technological effectiveness in medicine. In practice, we've done well at both, but they are only minimally connected logically. – Rex Kerr Nov 6 '11 at 16:51
  • 1
    "It is likely true that for a good portion of the world's population, physical fitness and reproductive fitness are being decoupled" - I think this is what I was really asking in my question, although perhaps I phrased it badly. In essence, if physical fitness and reproductive fitness are being decoupled now, when they need to be re-coupled at some point in the future (e.g. as a result of lack of resources), we as a race may be unsuited to continue surviving. In which case, I assume the evolutionary response would be extinction. – oliver-clare Nov 7 '11 at 9:05
4

Short answer: no.

"Survival of the fittest" means, as you point out, that the creatures most suited to their environment survive. What constitutes the environment, however, is not static, and necessarily changes over time. What is "fit" for one environment may no longer be fit as the environment changes: the dinosaurs are an object lesson here.

Furthermore, all creatures, by the very act of existing, have an impact on their environment, changing it sometimes subtly, sometimes blatantly. Humans are not an exception in this regard.

So: evolution is occurring, the same as it ever was.

In the case of your hypothetical: if the seventy grandchildren are able to go through life without breaking any bones, they are clearly fit to their environment. If not, they will die and fail to pass on their genes. So it goes. If an earthquake kills off all of those with brittle bones, then the survivors will go on to reproduce. If those survivors happen to not be human, then we join the dinosaurs. And so it goes.

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Evolution is not limited to genes ;) And Darwin did not knew about gene existence, as they were later discovered by Mendel.

Human is a notable creature that is evolving not by genetic means, but by means of 'culture'. This allows them to have long life span and generation cycles, together with high adaptation rate.

So when bacterias develop chemical resistance - we discover antidotes or gas masks, when mammals grow longer fur - we make warm cloth and houses, and so on.

So we would only be able to talk about human evolutionary plato - when there will be no scientifically, technological or social improvements in our civilization.

  • Premise is wrong. Evolution, in the sense meant by the OP (i.e. in the context of biology), is in fact limited to genes. Essentially, the question is: given that we can do all these things with culture, what's happening to our genetic makeup? – Rex Kerr Nov 5 '11 at 20:11
  • i quote OP - <<It is assumed, for the purpose of this question, that Charles Darwin, in the 19th Century, formulated the concept of "Survival of the Fittest".>> Read the book, and find me something about genes. If you can. – c69 Nov 6 '11 at 2:20
  • What a silly argument! If we talk about optics motivated by something written by Newton, do we have to pretend that we don't know Maxwell's equations or that it's still an open question whether light propagates through the ether? (Also, culture is not subject to the same heredity constraints that Darwin describes in many places.) – Rex Kerr Nov 6 '11 at 3:37
  • Silly or not, I happen to agree that the concept of "Survival of the Fittest" does not necessarily have to do with genes. A person with severe asthma can survive when their genes would otherwise prevent their survival, due to medicine. The difference is that, although it is the gene for asthma that's passed on, the reason for survival is not gene-related. Therefore humans have found a way to break the current sense of the word "evolution", which, as you correctly suggest, is entirely based around the concept of genes. – oliver-clare Nov 6 '11 at 10:42
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The last comment by LordScree points to the heart of the original question and the appropriate philosophical answer. Geneic changes take place randomly and support the survival of individual ( families over time ), species in varying environments. This is the common association of evolution with genes. But Richard Dawkins broke this link with his idea of a meme. Certain ideas are more effective - reproducable - and therefore fitter and reproduce. Combining these concepts, like any good philosopher, and you can concieve of 'evolution' meaning change over time; survival of the fittest meaning 'things = genes, ideas, culture, spending habits, cleaning habits' leading to reproductive success. In other words, evolution has brought humans to the point of decoupling evolution from strictly genetic change and incorporated 'self created' environments into the 'random' changes that lead to reproductive success.

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