The mod increases the speed of evolution. In the world of death, evolution is about 4 times faster.

Afaik evolution factor only gets increased on a) time passing, b) extra pollution, c) destroying spawners - https://wiki.factorio.com/Enemies#Methods_of_increasing

This mod does neither of these things by default, but if you've enabled "wisps fight biters" option, they totally can start killing spawners and hence increasing that factor.
If you have that disabled already, dunno what else it might be (except fallback "factorio bug" option), maybe you know what does it?

EDIT: oh, also, can suggest checking other mods that might do any of 3 things above (e.g. creating/removing pollution in spikes or something).

I checked, yes it is so affected by the "wisps fight biters" setting.
Test it yourself and add it to the description. Because evolution accelerates hard.

Yeah, probably deserves a special mention in description for that option at least, as I guess most people might not know how evolution mechanics work, so won't be obvious at all that this will happen if they enable it.
Thanks for the suggestion.

Replaced WARNING on that option to mention this in 0.3.20, as I think red wisps should be much more manageable now.
Also added as one of the hints to the README, so should hopefully be easy enough to spot in either of these places.

Is it possible though, to make them fight biters and biters fight them, without the biter vs train-roadkill evo-factor gets affected?

Hm, yeah, making biter nests immune to wisp attacks would probably do it.
Dunno if it's a universally good thing though, but should be possible to add a startup mod option for it.

It could be quite a challenge and add a bit of random event, if they ignored spawners, but somehow battle could break out between wisps and biters, burning down trees and what not (if using explosive biters), aggravating biters enough to launch an sudden attack on players.

Added default-enabled "Biter nests are immune to wisps" startup-tab mod option in 0.3.21 and moved evolution warning there.

It won't actually prevent wisps from occasionally attacking the nests, but biters should make short work of them when that happens, so should be hard to notice. Don't think factorio has any kind of "leave these things alone" lists for units (which is why biters occasionally "chew" on rocks and trees), and checking/interrupting attacking ones is probably too much hassle for such small thing.

aggravating biters enough to launch an sudden attack on players.

When biters flock together for an attacking party, pretty sure they'll be sending these herds to attack on their own as well, so it probably shouldn't add much surprise, but might keep triggering attacks faster at night, if disturbed herd always goes on a rampage.