Not only Intelligent Design - but DIVINE DESIGN!

Hi Anita, I'm sure others more knowledgeable than me will be along to address your other points, but I thought I should point out that this is untrue, as a quick look at the British Trust for Ornithology's Birdfacts site - http://www.bto.org/birdfacts/index.htm - will confirm. This site holds data gathered from decades of field research. I just looked at a few common British species beginning with C and found:Cetti's Warbler - 16-17 days
Collared Dove (pigeon family) - 17-19 days
Common Scoter (a duck!) - 30-31 days
Cuckoo - 11-13 daysNote the variation within each species too.It's also not correct to define incubation period simply as the time between laying and hatching, as consistent incubation (and thus development of the embryo) in many species does not begin until the clutch is complete - several days after the first egg is laid. This ensures the eggs all hatch at about the same time, despite their differences in 'age'.ETA - sorry, this was supposed to be a reply to Anita, not bluescat48...Edited by aiki, : replied to wrong message, somehow...

The figures I gave you are for actual incubation periods, not including the variable and irrelevant amount of time between laying and the start of incubation, when no embryonic development occurs. Even so, incubation periods are not consistent but vary by about 15% within a species, primarily because of temperature variation (source - BTO Birdfacts again).I don't think I understand what you're getting at in the second part of your message, but I see that Parasomnium already pointed out some of the many exceptions to the 'rule of seven' among mammals (I'm assuming that's what you mean by 'animals').