So what I understand is, evolution is a mere mistake in the replication of DNA and this change is sometimes good and sometimes bad.

And the other day, in our biology class, we were told the functioning of the lungs and how the RBCs fetch the O2 from the alveoli and dump the CO2 out.

And I also know a little bit about some complicated processes in the body like, how the digestive system works, how the muscle cells switch to anaerobic mode when we run out of O2 causing cramps, how the cells make ATPs in the mitochondrea.

And 1 more notable thing- the amount of complicatedness and all the neural networks in brain.

My question is- how can evolution(a mere mistake in copying a strand of DNA) make such a complicated machine, like our body. There are SO many organs, all working in collaboration to make the body work. And all of those organs are doing SO many things.

I know that this is a result of 3.8 billion years of evolution...but still... how can even a million "mistakes" make a body which is so well deisgned?

ALSO was the whitening of the polar bears a mistake too? Then what are the chances of such a mistake occuring in the replication of DNA? If it was evolution then why don't birds become the colour of the sky?

  • $\begingroup$ I'm afraid you need to learn a bit more about how evolution works. Evolution is not just a series of random mistakes, it also involves natural selection which is not random at all. A good starting point to learn about evolution is: evolution.berkeley.edu/evolibrary/home.php $\endgroup$
    – Roland
    Commented Jul 28, 2016 at 7:44
  • $\begingroup$ @Roland I know about natural selection- its like the survival of the fittest right? Like if there are 5 species of dogs in an environment, then only the fittest species will survive. $\endgroup$ Commented Jul 28, 2016 at 8:28
  • $\begingroup$ @Roland im a 10th grade kid and all the knowledge that i have gathered about evolution is from 2 or 3 youtube videos $\endgroup$ Commented Jul 28, 2016 at 8:29
  • $\begingroup$ Yes, that's natural selection. It acts as a "force" directing evolution, which means that the way things evolve is not random at all. Many people have questioned how evolution can come up with such incredible complex structures, but it does happen over billions of years, with countless organisms alive and evolving at any moment. It's really hard to grasp the enormous scale of it all. But evolution is a large topic, and we can't provide textbook material on this site, so check out the Berkeley page I mentioned for more information! $\endgroup$
    – Roland
    Commented Jul 28, 2016 at 8:48
  • $\begingroup$ @Roland ok, but 1 more question. Was there a species of animal with their brain not in their head? And maybe it went exist because the "brain in the heads" species was more fit? This is a silly question but it makes sense to me. $\endgroup$ Commented Jul 28, 2016 at 8:56

1 Answer 1


If this is a general question about how evolution works then Roland's comment is correct - you should start with one of the excellent resources available online, like http://evolution.berkeley.edu/evolibrary/home.php. However, this specific question sounds more like something we used to call the 'argument from personal incredulity' to me - you're willing to accept that evolution occurs, you're just not sure whether it is sufficient to create something as complex as the organisms you see around you. This is quite a common issue people have with evolution by natural selection, and it's a perfectly reasonable question to ask. Essentially, it originates in the difficulty of appreciating the sheer scale of the processes involved. To paraphrase Douglas Adams, "[life] is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is." But I'll do my best to try to help you understand this a bit better.

The number of single-celled organisms on the ocean floor is estimated at 2.9×10^29 - that's roughly three hundred billion billion billion. The current global human population is about seven billion - that's already effectively impossible to imagine. If every one of those people had seven billion tiny people living on them, and every one of those had seven billion people living on them, that's roughly the number of single-celled organisms on the ocean floor right now. Many of those appeared less than 24 hours ago and will be gone tomorrow. Natural selection is acting on every aspect of every one of those organisms simultaneously and has been doing for roughly 1.5 trillion generations. One-and-a-half thousand, thousand, thousand, thousand, thousand, thousand generations.

Natural selection is also a fantastic mechanism for homing in on solutions to complex problems - so good that we've started using it to solve mathematical and computational optimisation problems.

Essentially, it's one of the best approaches to solving complex problems we have been able to conceive of and it's had an insanely, mind-bogglingly long time to act on a planet-sized test tube. That's how we ended up with so much amazing stuff on our planet.

  • $\begingroup$ @arbrviral but still, like that complicated mechanics? Is the ability of the brain to switch itself off when we are hit on head also a mistake? Like I once saw in brain games that as light travels faster than sound, our brain perceives them both at the same time by lagging the light perception a little behind. Now that is a really complicated process and I don't think that was caused by a mere mistake and natural selection. If it was caused by natural selection then wouldn't some organisms might have existed on the planet who lag behind the sound perception? $\endgroup$ Commented Jul 28, 2016 at 11:04
  • $\begingroup$ @Adi: It's not by mistake. It's by natural selection. And yes, there have existed many individuals that lagged behind in many aspects when you compare them to existent individuals. many of those did not contribute to future generations because of their lagging behind. And there are still individuals that lag behind and they will also more likely not contribute to future generations. You have to keep in mind that what we see on earth today is a very, very, very (...) short evolutionary time frame, say a glimpse or a snapshot, and therefore not very informative. $\endgroup$ Commented Jul 28, 2016 at 11:29
  • $\begingroup$ @Adi Some aspects of any organism's environment are highly unpredictable; one is contact with parasites and pathogens, one is social environment. In situations like this the optimal response can be to evolve a system which is itself adaptive, rather than a pre-programmed solution. The brain and the immune system are the most obvious (and most complex) examples of this. I'm not sure I follow your brain-switching-off example, but this partially explains how we learn to integrate sensory inputs. See also: theguardian.com/education/2012/nov/12/… $\endgroup$
    – arboviral
    Commented Jul 28, 2016 at 12:42

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