Horizontal Gene Transfer: Sorry, Darwin, It's Not Your Evolution Any More

Horizontal gene transfer (HGT), sometimes called lateral gene transfer (LGT), is a profound recent discovery in genetics: Genome mapping has shown that bacteria can acquire genes from the bacteria around them --that is, horizontally -- rather than from a previous generation (vertical transfer), as when a parent cell divides into two daughter cells. They can transfer multiple segments of DNA at once to fellow species members.

But that was hardly the critical finding. This is: Because bacteria...