Just a small note: lateral gene transfer (= horizontal gene transfer) also exists in eukaryotes, although it’s much rarer than in bacteria. Nevertheless, the human genome is actually full of genetic elements that were originally transferred laterally from other organisms (virtually all of them via viruses). A “contemporary” example (i.e. a gene transfer that most people experience in their lifetime) is herpesvirus infection: Herpes simplex are retroviruses that introduce their own genetic material into the host’s.

It’s important to note that such viral infections generally do not infect germline cells and are thus not automatically inherited (though, like in the case of genital herpes, are easily transmitted to the offspring during birth).