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Most (if not all) industrialized countries follow a 7-day work week now, such that we are bound to follow a certain weekly trend in matters such as pollution generation, where to go (e.g. stay in town during weekdays, more likely to go to parks during weekends), what to do (mow the lawn on weekends).

Is there any evidence of any species evolving to adapt to the pace of the human 7-day week lifestyle?

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I think I could sketch out some of the premises for how it could happen, but unfortunately I'm unaware of any specific research (which is how you phrased the question) so I don't dare give that answer since it's not in your question –  deinonychusaur Oct 16 '12 at 10:39
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I have no clear evidence of a specific species, but two pieces of the puzzle:

  • species can adapt to living in cities: birds living in cities are bolder (i.e. allow humans to come closer before flying away), and apparently even some genetic changes can be detected.

  • it may be possible for species to evolve a circaseptan rhythm: beach beetles may have a seven-day rhythm to accommodate for different heights of the tides (spring/neap tide). (PubMed / PDF)

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Two comments: (1) The question asks about adaptation in an evolutionary perspective (which should be said is but a fraction of what is evolution (genetic drift etc. should not be forgotten!)). This implies that the there must have been a shift in the gene pool of the species that adapted. –  deinonychusaur Oct 17 '12 at 12:30
    
(2) Experiments on bacteria and yeast show that you can have a clonal population adapt to a severe selection in less than 200 generations. In fact some do in as little as 30. Taken with that the 7-day work week should only have been a relevant strong selection criteria (if it at all is) for about 100 years. That means that the species most probably has to have a short generation time with a maximum less than 3 years. But that said, I agree with you that there could be either a cognitive entity that adapts or a circadian. But to prove that it is the work week and not urban society at large! –  deinonychusaur Oct 17 '12 at 12:35
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And a suggestion: The bacteria "flora" in the stomach could in some humans have adapted to the tides of carbon-source/toxin shifts with the host behaving on the work-days and getting drunk etc on the weekends. –  deinonychusaur Oct 17 '12 at 12:36
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@deinonychusaur: I would also expect epigenetics to possibly play a role there... –  nico Oct 18 '12 at 5:19
    
@nico: I agree that epigenetics could lead to quick adaptation. But rather than causing the species to evolve, I'd say it's a way for the genotype to resist environmental change so that the genotype doesn't need to change (hence no evolution). Further, I find it hard to see how epigenetics could cause rewiring of the signaling network of a cell so that a new 7-day circadian rhythm would appear. It could, maybe, silence cautiousness or so in the first scenario (but once again, this would not be explicitly a 7-day week adaptation, nor an evolutionary process). –  deinonychusaur Oct 18 '12 at 12:32
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