Thus, we have Digimon who look like angels, devils and dragons alongside ones that look like (outdated concepts of) dinosaurs, insects, and plants, and it all happily makes sense. This is why Digimon is awesome.
Then there's Xros Wars, which seems to throw the concept into question with this conversation, involving human kid Taiki and extremely knowledgeable scientist wizard Wisemon:
This is a really strange idea, and one that I kind of feel the writers fumbled a bit. Xros Wars plays with a lot of interesting notions, but if you're going to drop a bombshell like this, you need to go into it a bit further and then actually explain what's actually up with the Digital World if it doesn't work like the traditional one*. Near as I can tell, this is the only time the subject's brought up in the whole series, and I've yet to see any sites make reference to the fact that Xros Wars had this statement in it**. (I've perused two different Digimon wikis and also TVTropes rather heavily. None of the sites mention it.)
*And because Xros Wars includes the time dilation effect seen in Digimon Adventure 01, where the Digital World's time flow is much faster than that in the human world, it's not even necessary to do this to explain away why the Digital World can have such a long history when digital technology and the Internet are so comparatively young. Heck, something like six months goes by when Taiki returns to the human world for an evening, night, and morning. That means that nearly a year goes by every real-world day. The simplistic histories that the Digital World generally gets would never really need much more than the few thousand years*** that even Digimon Adventure got.
**Admittedly, the Digimon fandom is full of angry people who think it should only ever be Digimon Adventure and hate anything from another series that doesn't match up with Adventure. These people are as annoying in this fandom as the GEEWUNNERS are in Transformers. Also, Digimon Tamers is the best-written Digimon series bar none, even if Xros Wars is something of a personal favorite of mine. I say this as someone who usually dislikes the grimdark approach that Tamers took.
***If the Digital World formed from the Internet of the early '90s, let's say around 1993, it would have had about eight years until Adventure 01 started, give or take. At a "day per year" rate, which is a little higher than it actually is but close enough for
...Is it terribly obvious I've put a lot of thought into this?