[jefftk]

> It'd be weird for evolution to struggle so much on trying such a simple concept somewhere.

While "building it backwards" sounds simple to us, it's not simple at all in evolutionary space. Evolution operates over a fitness landscape, where every configuration of an organism has some fitness (essentially, probability of reproducing). It can make good progress as long as there are paths that don't require traversing areas of impractically low fitness. The problem in this case is that between "normal" and "mirror" is an area of absurdly low fitness, which evolution shouldn't be expected to be able to cross.

[roenxi]

We can't really say what is hard, because evolution tends to be more creative than anyone expects. But we can say it sounds easy - evolution would only need to come up with a "build this with reverse the chirality" mechanism and run everything through it. That'd even be what humans are doing in this research, I suspect. If there are advantages to reversing chirality then there'd be lots of paths where partially reversing chirality of parts of an organism would be interesting or creating clouds of reverse-chirality molecules would be evolutionary powerful.

It wouldn't be likely, but we're talking millions of years and a process that has overcome some remarkable engineering challenges. Finding one place where building backwards then extending that just wouldn't be such a big deal.