In Darwinian evolutionary theory, does the environment has any role?

To state it clearly:

Suppose I have an isolated system. First, I place several types of entities (organisms) in an environment. According to Darwin, eventually, the fittest will survive.

Next time, I place Only one organism. Will it survive this time as there's no one else in the system? If not, did Darwin also consider the whole environment as another entity, so that in the above case, there are two entities, the organism and the environment. The environment is more evolved and it survives, other dies?

Moreover, if the climate is favourable and the organism reproduces sexually results in the same fate as the case if climate is unfavourable, organism reproduces asexually, what conclusion does it leads to?

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    $\begingroup$ For a great introduction to modern evolutionary theory, check out Understanding Evolution from the University of California, Berkeley. Darwin (and Wallace) may have originated the first coherent theories of evolution, but things have changed a lot since then. The environment absolutely has a role in evolution, otherwise there would be no stimulus to evolve. Additionally, there's no such thing as a truly isolated system - predators need prey, all depend on plants and/or other organisms that depend on the sun, etc. etc. $\endgroup$
    – MattDMo
    Jul 6, 2016 at 18:31
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    $\begingroup$ I don't think you understand Darwin's argument very well. Organisms never evolve. If you place one organism, there's nothing to evolve, so your question is meaningless. Populations evolve. If the organism produces a population (i.e. through its progeny) then there is room for evolution on the population. $\endgroup$
    – iayork
    Jul 6, 2016 at 18:32
  • $\begingroup$ Those best adapted to their environment will reproduce. Fitness is a value judgement. Take a human with sickle cell anemia and place them in the Himalayas and they will suffer terribly and likely die before they can reproduce. Place the same person in a jungle type environment, and maybe they are better adapted to survive until they reproduce as they are resistant to malaria, where as a Sherpa might quickly fall ill in the jungle and die from trypanosomiasis before reproducing. Both organisms are "fit" just in different ways that the environment places pressures on. $\endgroup$
    – AMR
    Jul 6, 2016 at 20:47
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    $\begingroup$ Fitness has no meaning without the environment. There is no absolute fitness. Fitness is always with respect to a given environment. $\endgroup$
    Jul 7, 2016 at 5:55

1 Answer 1


"According to Darwin, eventually, the fittest will survive"

Darwin never said this. Fitness and survival are two separate concepts.

In a simplistic version, fitness is measured by reproductive output. Survival is, well, survival. You can have higher output than your brother, but have a lower chance survival. In fact, the very act of producing offspring can negatively affect your ability to survive.

No, the environment is not an other organism, in any context. It is the place (stage, arena, etc) in which the measure of fitness (reproductive output) can be measured. The environment can directly influence and affect fitness, and other organisms (inter and intraspecific) ARE part of that environment.

A single isolated organism does not evolve, but can have offspring. However, you need a more than one organism for fitness to have any meaning in a Darwinian model.

  • $\begingroup$ It would have to be a bacterium or "simple" eukaryote that either replicates asexually or through self fertilization in order to have offspring if they are isolated. Mammals, reptiles etc. need certain levels of organisms in a population to allow for successful enough reproduction to maintain the species above extinction. $\endgroup$
    – AMR
    Jul 6, 2016 at 20:53
  • $\begingroup$ Yes, but it makes do difference to the central concept of fitness vs survival. I did not qualify the organism in isolation. $\endgroup$
    – theBIOguy
    Jul 6, 2016 at 20:54
  • $\begingroup$ Prokaryotes and viruses (even prions) can have fitness. Anything that replicates with information persistence can have Darwinian fitness. $\endgroup$
    – theBIOguy
    Jul 6, 2016 at 20:55
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    $\begingroup$ -1: I don't think your answer is particularly clear or well constructed, has no references or supporting material, and generally does a poor job of answering the question. $\endgroup$
    – rg255
    Jul 7, 2016 at 5:19
  • $\begingroup$ Fitness is a function of both reproductive success and survival. The answer is wrong. $\endgroup$
    – Remi.b
    Jul 26, 2016 at 1:28

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