It’s usually mediated by viruses. A virus infects an organism, picks up some host genetic material, and later jumps to a different host. At some point, the viral DNA is incorporated into the host genome and stays there, bringing the DNA from the previous host with it. This is how mammals got placentas. About 8% of the human genome is made of viruses that got stuck there

There are conservatives on Mastodon, but the rest of the Fediverse defederates the explicitly conservative instances. The big ones are Gab, Parler, and TruthSocial, which don’t seem to federate with anybody at all. (I would advise against looking them up, because they have a rather high concentration of Nazis).